Locomotion Lab Outline
Introduction
C. elegans
Caenorhabditis (see-no rab-dye-tis) elegans (C. elegans) is a species of non-parasitic, non-pathogenic roundworms (Phylum: Nematoda). The life cycle of the nematode can be seen in figure 1. Nematodes are a model organism used in research labs around the world, including here at McMaster University. This includes the Nematode Biodiversity Project (Dr. Dej; School of Interdisciplinary Science), studying developmental biology and regulation of gene networks (Dr. Bhagwati Gupta; Department of Biology) and how age-related disorders develop (Dr. Leslie MacNeil; Department of Biochemistry and Biomedical Sciences).
When placed on nematode growth media (NGM) plates, C. elegans move in response to environmental cues using rhythmic, undulating and oscillating body motions that resemble a sinusoidal wave-like pattern (figure 2). The particular pattern of movement is a result of the coordination by the neuromuscular system. The nervous system of C. elegans is made up of 302 neurons. These include sensory neurons, which detect changes in environmental conditions and relay signals to central processing centers. These processing centers contain interneurons that are able to integrate sensory information with motor neuron activity. It is then the direct control of muscle activity by 75 motor neurons that coordinates the undulating movements of the worm. Being able to coordinate movement seems to be a complex task for such a small, 1-1.5 mm long organism, but imagine scaling the control of locomotion to a human, who can have as much as 100 billion neurons in the body!
One of the unique aspects that makes C. elegans a great model organism is that we can investigate the coordination of physiological processes (such as movement) and correlate this knowledge with how humans regulate the same processes. Being such small organisms that can be easily manipulated also makes C. elegans a great model to investigate the effects of aging and aging-related disorders on neuromuscular activity. This is easy to do since there are mutant or knockout strains for almost every C. elegans gene available to order from work repositories (e.g. Caenorhabditis Genetics Center) or from research labs which have engineered their own strains. This enables us to identify how gene products correlate to their function, and also enables us to investigate how physiological processes (such as movement) can be affected with disease and aging.
Protein Aggregation
Aging is a complex biological process that involves changes in molecular and cellular behaviours that in turn impact tissue and system health and function. Cellular aging is accompanied by an increasing number of toxic protein aggregates in the cells. These aggregates are correlated with various neurodegenerative disorders, such as Alzheimer’s, Huntington’s, and Parkinson’s disease. Researchers are trying to identify how protein aggregation might cause the observed cellular and tissue-level phenotypes seen with these diseases.
Modelling Protein Aggregation in Living Systems
Protein aggregation can be studied using a number of biological model systems, including the C. elegans. The strains we are using today have been developed by the Morimoto lab at Northwestern University. These strains produce fluorescently labelled protein aggregates in the muscle cells of its body wall (figure 3). The effect of knocking down various proteins (e.g. through RNA interference; RNAi) on the size and amount of these aggregations can be used to identify proteins involved in the unfolded protein response, which is crucial for understanding these neurological diseases. However, there are limitations to using this C. elegans model for studying neurological disease pathology for a number of reasons. For instance, the protein aggregations in these disease states actually occur in neurons, not in the muscle cells like we see in this model. However, this is still a good model for studying the unfolded protein response (UPR) which is activated in response to an accumulation of unfolded or misfolded proteins in the lumen of the endoplasmic reticulum, and how dysfunction of this response can affect protein aggregations that contribute to these neurological diseases.
The video below is from a different strain of C. elegans that contains a green fluorescent protein (GFP) in the muscle cells. You can observe these organisms under a stereomicroscope. In this video, C. elegans movement is being influenced by chemotaxis – movement of the organism triggered by following chemical gradients in the surrounding environment.
LSL Video Locomotion – C. elegans
Investigating UPR and protein aggregation disorders with C. elegans
The AM138 (Q24), AM140 (Q35) and AM141 (Q40) strains are being used in the lab today. These strains carry a yellow fluorescent protein (YFP) fusion under the regulation of a muscle-specific (myosin heavy chain) promotor (unc54p). This means that the YFP localizes to just the muscle cells of the organism, as that is where the protein is expressed in the nematode. In the Q0 strain of nematode, the proteins tagged with YFP show a diffuse (soluble) distribution throughout the body wall muscle cells their whole lives. However, the construct in the AM141 strain (“Q40”; unc54p::Q40:YFP) also contains a poly-glutamine repeat (polyQ), Q40 (N=40 glutamines) fused in frame with YFP. Immediately after hatching, there is a soluble distribution of the polyQ:YFP protein in the muscle cells of the body wall. As the nematode ages, these polyQ:YFP proteins form aggregates within the muscle cells of the body wall, which affects its locomotion. The number of aggregates is proportional to the poly-glutamine expansion length. There are actually dozens of these varying strains, each engineered with a different length of aggregation – fluorescent images of 9 of these strains are shown in figure 4, including the Q35 and the Q40.
These worm strains are often utilized to study how aging can contribute to physiological accumulation of protein aggregates and cellular toxicity. This models the various neurodegenerative and neuromuscular diseases including Alzheimer’s, Parkinson’s, amyotrophic lateral sclerosis (ALS), and Huntington’s diseases. This is a model only, because the expression of these protein aggregates is in the muscles, where we would find these aggregates in the neurons in the human diseases.
Interestingly, the potential for aggregate formation with increased poly-glutamine repeats is not only regulated by a muscle-specific promotor (e.g. as seen in the AM141 (‘Q40’) strain). There are strains available that contain the poly-glutamine repeats that are induced for expression by neuron-specific promoters. Aggregate formations in these neuron cells are similar to the aggregate formation phenotype observed in muscle cells. Then this provides further evidence that wildtype and mutant strains of C. elegans can be used to model both neurodegenerative and neuromuscular disorders.
Table I provides a summary of the genotype and phenotype of these 3 mutant strains we are specifically using today.
Table I: Description of Nematode Strains Used in the 2L03 Lab. Strain ID corresponds to the ID# for ordering this strain from the Caenorhabditis Genetics Center (CGC).
| Strain ID | Genotype | Phenotype |
|---|---|---|
| AM 138 "Q24" | rmls130 [unc-54p::Q24::YFP] | Diffuse distribution of Q24::YFP throughout body-wall muscle cells. Worms maintain a soluble phenotype during their lifespan. |
| AM140 "Q35" | rmls132 [unc-54p::Q35::YFP] | Animals show a Q35::YFP progressive transition from soluble to aggregated as they age. |
| AM141 "Q40" | rmls133 [unc-54p::Q40::YFP] | Animals show a soluble Q40::YFP distribution in their body wall muscle cells immediately after hatching. However, as the nematodes age, foci (aggregated protein) are observed. When they reach adulthood, animals show an entirely Q40::YFP aggregated phenotype. |
You’ll want to watch the video about how to use the Zen Stemi305 stereomicroscope before coming to lab this week – this microscope is different from a compound light microscope in that the you’ll retain 3-D view of the materials you are working with (with a compound light microscope, you are reduced to a 2-D plane that you are viewing, and the image has no depth of field). You may also hear stereomicroscopes called “dissecting” microscopes, as they facilitate microdissection activities on small organisms like nematodes or fruit flies, which would not be possible with normal human vision! Please refer to Appendix E: Zeiss Stemi305 Stereomicroscope to learn about the operation of the stereomicroscope.
Lab Overview and Timeline
| Time (min) | What will you be doing? | Total Time (min) |
|---|---|---|
| 0 - 10 | Overview of lab activities by the TA. | 10 |
| 10 - 50 | Lab Part 1: Mechanosensory Response Assay Lab Protocol 1 - Mechanosensory Response Assay |
40 |
| 50-90 | Lab Part 2: Thrashing assay using C. elegans Lab Protocol 2: Collecting your worms Lab Protocol 3: Capturing Videos of Nematodes during Thrashing Assay Ensure all data is in the class dataset by the 90 min mark. |
40 |
| 90-170 | Clean up your workstation Complete and submit your ELN in PAIRS |
80 |
Lab Part 1: Mechanosensory Response Assay (‘touch-test’)
Purpose
To practice manipulation of objects under a stereomicroscope, and collect data regarding behavioural differences in various nematode mutations to observe the differences between organisms related to protein aggregation in the muscle cells of the body wall.
Summary of Activities
You will be conducting a mechanosensory response assay with the same mutant strain of nematode you used from Part 1. This time, you’ll be using nematodes still on the surface of their NGM agar plate, and you will touch the nematode on the head with a fine paintbrush and observe whether they retreat away from the stimulus (what is called a “backing” response) or if they do not react. This will provide an indicator of the functionality of the mechanoreceptors in the organisms in response to stimuli.
Form two pairs at your stations. Each pair will work together with one petri dish of nematodes. Record your data in table II.
Materials
A. Plastic transfer pipettes
B. plate of nematodes – will be ONE of three types of nematodes used by you and your partner
- Q24 nematodes (AM138)
- Q35 nematodes (AM140)
- Q40 nematodes (AM141)
C. empty plates for conducting experiments
D. M9 buffer jar
E. P20 pipette tips
F. P1000 pipette tips
G. 15 ml conical tubes for collecting nematodes in Part 2
H. micro-brush for Part 2 (THESE ARE REUSABLE! DON’T THROW AWAY!)
I. permanent marker for labelling plasticware
J. P1000 micropipette
K. P20 micropipette
Not shown in image:
- Stemi305 Stereomicroscope
- Computer set up with Zeiss Zen software
- tips waste container
- liquid waste container
- Benchtop centrifuge (the TA will operate this today)
- cell counters
- stopwatches
Safety Reminders
There are potential risks associated with these lab activities that you should be aware of, including but not limited to:
-
- The food source for nematodes is E. coli (OP50) which is found on the agar layer of the petri dish you get the nematodes from. Use caution working with the nematode plates and M9 buffer of nematodes, wearing gloves and ensuring not to touch your personal belongings or face with your gloves!
- Centrifuges are extremely dangerous if not properly loaded. Your TA will be supervising centrifuge usage in this lab, and the centrifuge should never be turned on if not properly balanced.
Lab Protocol 1: Mechanosensory Response Assay
LSL Video Locomotion – Mechanosensory Response to micro-brush contact
- You will select a petri dish with NGM media and nematodes in it. Make sure you record which strain of nematodes you will be working with today (e.g., Q35).
- You’ll be removing the lid of the petri dish for this activity, so you can interact with the nematodes on the plate. Do this before you start adjusting the focus, or you’ll need to adjust again when the lid comes off.
- Place the NGM plate under the stereomicroscope and adjust the coarse focus and magnification until you can see several nematodes.
- Increase the magnification until you are viewing one specific adult nematode. You can move the plate around under the field of view to adjust as required.
- You will not be using the computer/microscope camera for this part, because the field of view through the eyepieces is much easier to work with for this activity.
- You will use the micro-brush and gently brush the bristles across the head of the nematode you are viewing. Observe the response, and give the nematode about 20s to recover from the poke.
- How can you tell which end of the nematode is the head? Watch it move a bit – the nematode will naturally be travelling head-first, with it’s tail dragging along behind it.
- Repeat this touch test four more times, recording the response each time.
- Generate a score for this nematode /5, where the nematode receives 1pt for each backing away in response to the paint brush poke, and 0pts for each time it does not respond. Record this score in your downloaded copy of Table II.
- Move the NGM plate a bit and locate a different nematode. Repeat the touch test again, poking the nematode on the head 5 times, with rests in between, and recording a score /5.
- Complete the touch test for 5 nematodes on your NGM plate, recording the scores as you go.
Lab Part 2: Thrashing assay using C. elegans
Purpose
To practice working with the stereomicroscope and Zen software, and to experience working with a model organism and scoring behavioural data related to muscle-localized protein aggregation.
Summary of Activities
You will use the stereomicroscope and Zen software to capture short (~30s) videos of the Q24, Q35 and Q40 nematodes moving in a droplet of M9 buffer. You will then count the number of body motions for each worm during an elapsed time of 30 seconds. This will allow you to investigate the effects of age-related disorders (specifically, polyQ-repeats) on the locomotion of C. elegans. Record your data in table I.
Materials
- Same as part 1
Lab Protocol 2: Collecting your worms
- Using a p1000 micropipette, wash the surface of the petri dish with 0.5 ml of M9 buffer 4 times, transferring the liquid into a 15 ml conical tube each time. Be careful not to overfill the plate!
- NOTE: you should swap tips on the pipette after each wash. This is so you don’t put worms in the M9 buffer jar when you get your next 0.5 ml out!
- This 15 ml conical tube now contains the nematodes that were on the surface of the NGM plate, in addition to 2 ml of M9 buffer. You will label your tube with your pod name, and take your tube over to the TA to centrifuge.
Why are we centrifuging our nematodes? Won’t that hurt them?
-
- Nope! The forces being applied during this centrifugation are not high enough to damage the organisms. Instead this will create a “pellet” of worms in the bottom of the conical tube, leaving the liquid buffer on top.
 You will use the plastic transfer pipette to remove the extra M9 buffer on top of the pellet, leaving ~1 ml of buffer in the tube with the worm pellet.
- Now, the worms need to be resuspended! Use the plastic transfer pipette to gently pipette the remaining M9 buffer up and down over and over again, creating turbulence to mix up the worms in the pellet with the buffer. You’re creating a HOMOGENOUS solution of worms and buffer.
Lab Protocol 3: Capturing Videos of Nematodes during Thrashing Assay
- Using the P20 micropipette, you will draw up 10 μl of resuspended worms and place this droplet onto a fresh petri dish (not containing any agar).
- Place the petri dish under the stereomicroscope. Bring the droplet into focus, increase the magnification as required, and identify how many adult worms you have within the droplet. You can refer back to Figure 1 to refresh your memory about the life stages of the nematode.
- If there are too many worms – add another 10 μl of M9 buffer to dilute your droplet.
- If there are not enough worms – add another 10 μl of the resuspended worm solution to increase the number of worms in the droplet.
- Connect the stereomicroscope camera to the computer, and open the Zen software.
- Place 1 (or more) adult nematodes in the field of view of the microscope camera on the software. Ensure the live view of the camera is in focus.
- Following the instructions for recording videos using Zen (see Appendix F: Zen Software). The relevant part of this appendix for this protocol is part 5. You will capture 30s of video for each organism, using the stopwatch to measure the time you are recording.
- Save the file with a descriptive title so you remember the organism strain information, as well as your pair info so you can easily identify the video afterwards. Be sure to stick to B/W videos, or the files will get too large!
- You can skip saving the videos as files if you just watch back the video in the Zen software. Ensure you’ve recorded a 30s video exactly using the stopwatch, and then you can count the thrashes within Zen instead.
- Open the video file on the computer, and watch the video through, recording how many FULL body thrashes take place in the elapsed 30 seconds. If the video is longer than 30s, you won’t count thrashes after this time.
- A full body thrash is when the nematode swings it’s body from the midline all the way to the left, back through the midline, all the way to the right, and back to the midline.
- You can use the counters to help record thrashes while you watch back the video.
- Record the number of body thrashes for your organism in Table I.
- Repeat this process for 5 worms. Note: You may have more than one worm in a single video, so you can double up on data for that recording, counting the thrashes for one worm first, then counting the second worm, giving each of them their own value in your list of 5 recorded worms.
- When you are done collecting your data, you will add your 10 values to the class dataset. Clean up your station, turning off the microscope and putting the nematode plate you were using for this assay in the discard pile on the central lab bench – these plates are now empty, so they won’t be reused, and we’ll be bleaching them to disinfect them before disposal. The micro-brush should be sprayed with 70% EtOH (recall, there is OP50 E. coli on the plate, so we want to disinfect the paint brush), and the bench top can be sprayed and wiped down as well. Do NOT throw away the micro-brush!
- Once all data is collected, the TA will post the class data set on Avenue for you to begin your analysis. We will be aiming to complete the class data spreadsheet by the 90 minute mark – if students have not completed their data collection by this time, we’ll move on with the partial dataset so student pairs have time to complete the graph for the ELN.
LSL Video Locomotion – C. elegans movement in water
(Video by Clint Reynolds, YouTube, 2012.)
Let’s consider the experimental design of today’s lab a bit!
What are the differences between the replicate measurements taken in the two activities today?
- Thrashing Assay:
- We counted the number of thrashes in 30s for 5 unique nematodes.
- Each of these nematodes was the same mutant strain in your personal data tables (although different pairs worked with different strains, to allow for data to be collected for all 3 strains for the class dataset)
- Mechanosensory Response Assay (touch-test):
- 5 unique nematodes were assessed by each pair of students
- For each unique nematode, the touch-test was repeated 5 times, to generate a score out of 5
Technical Replicates: these are replicates taken within the same biological sample (this could be a cell, a human, a cat, a nerve, etc.) They show if there is any variability of the protocol. An example of this was when you did the aging and frailty chair stand test multiple times, or when you counted the cells from your cell suspension ten times, using each of the grid squares across the two sides of the haemocytometer.
Biological Replicates: these are the same type of measurement but in different biological samples. These biological samples can be considered to be part of the same treatment group for this definition here, but this isn’t a perfect rule for the full field of science! An example of this was in the epidemiology lab, where you ran each NetLogo simulation multiple times.
Treatment Groups: Treatment Groups should receive a different experimental intervention between them, with the rest of the variables controlled. When you design an experiment, you want to consider to what extent both technical and biological replicates will play a role within each of your treatment groups. (E.g., how many mice will be in each treatment group? How many times will you test each mouse? How many treatment groups are there?)
Can you identify which type(s) of replicates were used for each of the two experiments today?
With your partner, consider the following experimental design features of today’s class data set:
- What is the hypothesis/prediction for each experiment? (i.e. what are we expecting we will see when we analyze the class data set during the ELN?)
- What is the independent variable? (Was it something intrinsic to the organisms, or was it something related to the procedure we executed?)
- What is the dependent variable? (Note: there are two, since there were two experiments with different endpoints!)
Lab Exit Checklist
- Thrashing assay scores collected for 5 nematodes from your pair, using the Zen software, and recorded in your personal copy of Table I
- Touch-test scores collected for 5 nematodes from your pair, using just the stereomicroscope (no videos for these!), and recorded in your personal copy of Table II
- Scores from Table I and Table II transferred to the class dataset for each assay. NOTE: the mutant you collected this data from is very important, please don’t forget to indicate this in the class dataset
- Clean up your station for the next group of students:
- All tips waste into the tips waste container
- Any waste buffer in the liquid waste container
- Plastic transfer pipettes and petri dishes used for assays in the solid waste container on the TA bench (we need to bleach these before disposal)
- Gloves in biowaste box (yellow bag cardboard box)
References
Altun, Z.F., & Hall, D.H. (2009). Introduction. In WormAtlas. doi:10.3908/wormatlas.1.1
Brignull, H.R., Morley, J.F., Garcia, S.M., & Morimoto, R.I. (2006). Modeling polyglutamine pathogenesis in C. elegans. Methods in Enzymology. 412: 256-282.
Gjorgjieva, J., Biron, D., & Haspel, G. (2014). Neurobiology of Caenorhabditis elegans locomotion: Where do we stand? BioScience, 64(6): 476-486.
Morley, J.F., Brignull, H.R., Weyers, J., & Morimoto, R.I. (2002). The threshold for polygluatmine-expansion protein aggregation and cellular toxicity is dynamic and influenced by aging in Caenorhabditis elegans. PNAS, 99(16): 10417-10422.
Nussbaum-Krammer, C.I., Neto, M.F., Brielmann, R.M., Pedersen, J.S., &Morimoto, R.I. (2015). Investigating the Spreading and Toxicity of Prion-like Proteins Using the Metazoan Model Organism C. elegans. J. Vis. Exp. 95(e52321). doi:10.3791/52321
Volovik, Y., Marques, F.C., & Cohen, E. (2014). The nematode Caenorhabditis elegans: A versatile model for the study of proteotoxicity and aging. Methods. 68(2014): 458-464.


What the literature says
Literature Review
Sandra Law
Identifying Gaps in the Literature
The areas of focus for this literature review will be 1) underdiagnosis of autistic women 2) the experience of autistic students transitioning to postsecondary education 3) the kinds of supports provided to autistic students, specifically 4) autistic student perceptions of supports and accommodations that are provided to them 5) faculty perceptions of students with disabilities
Underdiagnosis of Autistic Women
Women with autism often receive their diagnoses much later in life than their male counterparts. Some women are diagnosed at the same time as their children, others struggle through life receiving a number of misdiagnoses until finally receiving a correct diagnosis of autism (Beckwith-Fellows, 2017; CBC, 2018). Women who have autism may excel at the primary and secondary school levels but decide to forgo pursuing postsecondary education because of their own low levels of confidence in their abilities (Kim, 2015; Stark, 2019). Women’s skill at masking their symptoms, essentially hiding their struggles from peers, friends, teachers, parents and professionals (McCann, 2017) may be one reason for their later diagnoses. Receiving a diagnosis later in life means that women lose out on a number of supports that are provided to individuals with an autism diagnosis prior to the age of 18 (Lehnhardt et al., 2016; Milner et al., 2019; Stark, 2019). Anderson, Carter, & Stephenson (2018) argue that the needs of women in postsecondary education may be greater than those of men. In addition, their needs may not be well-understood and are generally not being met, given the limited amount of research on sex-based differences in autism.
Experiences of Autistic Students in Postsecondary Education
More and more autistic students are pursuing postsecondary education (Widman & Lopez-Reyna, 2020; Gurbuz et al., 2019). The number of autistic postsecondary students is likely underestimated as many of these students fail to register with disability services (Ames et al., 2016; Cai & Richdale, 2016). Even autistic students who are well-prepared academically may struggle to succeed in postsecondary education (Baldwin et al., Ma et al, 2016). Despite the increased participation of autistic students in postsecondary education there is a shortage of programs that specifically address their needs (Chown and Beavan, 2012). A common theme amongst autistic student accounts of their postsecondary experience is that they feel isolated and lonely and encounter barriers communicating with other students (Ariel & Naseef, 2006; Francis, Duke, Fujita, & Sutton, 2019). This contributes to lower program completion rates for autistic individuals (Adreon & Derocher, 2007; Gotham et al., 2015).
Supports Provided to Autistic Postsecondary Students
There is a lack of clarity about the specific needs of autistic students in postsecondary education. Students who received some preparation (e.g., through postsecondary programs) in transitioning to postsecondary education likely have improved outcomes (i.e., increased program completion rates) (Greenberg, 2020). One of the difficulties inherent in providing supports to autistic postsecondary students is that they are a heterogeneous group. As one autism researcher has put it ‘if you have met one person with autism, you have met one person with autism’. Most of the accommodations provided to autistic students (e.g., separate testing space) were developed to serve the needs of other types of disabled students (Anderson, Stephenson, Carter, & Carllno, 2019). It has been suggested that most of the supports offered to autistic students are a poor match to their actual needs given that they are focused on academic supports when the needs of autistic people may be in non-academic areas (Gelbar et al., 2015). Even when postsecondary institutions do offer specialized supports to autistic students, students may not take advantage of them for a variety of reasons, such as,
- not being aware that supports exist,
- inability to understand that they need help, and
- stress response that impairs ability to request support.
Elias & White, 2018; Gaffney, 2020; Knott & Taylor, 2014)
Autistic Students Perceptions of Supports and Accommodations
A multi-year, single institution study conducted by Accardo et al. (2019) on student satisfaction with accommodations and supports provided by a university indicated that students felt misunderstood by university faculty/staff, which in and of itself, was a barrier. Students also identified accommodations that they felt would have helped them succeed, such as: quiet locations for exams, a notetaker for lectures, extended time for assessments, academic coaching, housing accommodations, tutoring, and counseling (Accardo et al., 2019).
Faculty Perceptions of Students with Disabilities
Different educators have different degrees of willingness to support accommodation requests (Easterbrook et al., 2015). They may also have different levels of awareness of the range of disabilities their students may have and understanding of their legal responsibilities towards students (Muller, 2006). Faculty members are more likely to support students with disabilities when they have been given some training about the general needs of students with disabilities (Austin & Pena, 2017). It may be that faculty and staff are simply unaware of autistic students in their courses, as many of these students choose not to disclose their status (Kelly & Joseph, 2012). Although there are pedagogical strategies that have proven to be effective with autistic students there is little evidence that they are known or used by faculty members (Austin & Pena, 2017).


92 Chapter 8 Overview
What You’ll Learn To Do: Examine and identify Ancient Roman art.
In Chapter 8 we will examine Ancient Roman art. We will look at how this art contributed to the larger development of Western art. It is imperative to understand Ancient Roman art in order to see how it impacted later artistic developments.
Learning Activities
The learning activities for this module include:
- Review: Key Learning Items
Introduction
- Watch: Ancient Rome (13:46)
- Watch: Digging Through Time (2:26)
Roman Republic
- Watch: Temple of Portunus (3:10)
- Watch: Veristic Male Portrait (2:58)
Roman Empire
- Watch: The Pantheon (8:31)
- Read: Augustus of Primaporta (includes a video—4:52)
- Watch: Painted Garden (4:03)
- Watch: Head of Augustus (5:15)
- Watch: Ara Pacis (10:40)
- Watch: Villa of Mysteries (9:12)
- Watch: Colosseum (8:33)
Extra Review
- Review: External Resources
Assignment
- Submit: Module 8 Quiz (5 points)


19 Periodic Variations in Element Properties
[latexpage]
Learning Objectives
By the end of this section, you will be able to:
- Describe and explain the observed trends in atomic size, ionization energy, and electron affinity of the elements
The elements in groups (vertical columns) of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number and distribution of electrons in their valence shells. However, there are also other patterns in chemical properties on the periodic table. For example, as we move down a group, the metallic character of the atoms increases. Oxygen, at the top of group 16 (6A), is a colorless gas; in the middle of the group, selenium is a semiconducting solid; and, toward the bottom, polonium is a silver-grey solid that conducts electricity.
As we go across a period from left to right, we add a proton to the nucleus and an electron to the valence shell with each successive element. As we go down the elements in a group, the number of electrons in the valence shell remains constant, but the principal quantum number increases by one each time. An understanding of the electronic structure of the elements allows us to examine some of the properties that govern their chemical behavior. These properties vary periodically as the electronic structure of the elements changes. They are (1) size (radius) of atoms and ions, (2) ionization energies, and (3) electron affinities.
Explore visualizations of the periodic trends discussed in this section (and many more trends). With just a few clicks, you can create three-dimensional versions of the periodic table showing atomic size or graphs of ionization energies from all measured elements.
Variation in Covalent Radius
The quantum mechanical picture makes it difficult to establish a definite size of an atom. However, there are several practical ways to define the radius of atoms and, thus, to determine their relative sizes that give roughly similar values. We will use the covalent radius ((Figure)), which is defined as one-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond (this measurement is possible because atoms within molecules still retain much of their atomic identity). We know that as we scan down a group, the principal quantum number, n, increases by one for each element. Thus, the electrons are being added to a region of space that is increasingly distant from the nucleus. Consequently, the size of the atom (and its covalent radius) must increase as we increase the distance of the outermost electrons from the nucleus. This trend is illustrated for the covalent radii of the halogens in (Figure) and (Figure). The trends for the entire periodic table can be seen in (Figure).
| Covalent Radii of the Halogen Group Elements | ||
|---|---|---|
| Atom | Covalent radius (pm) | Nuclear charge |
| F | 64 | +9 |
| Cl | 99 | +17 |
| Br | 114 | +35 |
| I | 133 | +53 |
| At | 148 | +85 |
As shown in (Figure), as we move across a period from left to right, we generally find that each element has a smaller covalent radius than the element preceding it. This might seem counterintuitive because it implies that atoms with more electrons have a smaller atomic radius. This can be explained with the concept of effective nuclear charge, Zeff. This is the pull exerted on a specific electron by the nucleus, taking into account any electron–electron repulsions. For hydrogen, there is only one electron and so the nuclear charge (Z) and the effective nuclear charge (Zeff) are equal. For all other atoms, the inner electrons partially shield the outer electrons from the pull of the nucleus, and thus:
Shielding is determined by the probability of another electron being between the electron of interest and the nucleus, as well as by the electron–electron repulsions the electron of interest encounters. Core electrons are adept at shielding, while electrons in the same valence shell do not block the nuclear attraction experienced by each other as efficiently. Thus, each time we move from one element to the next across a period, Z increases by one, but the shielding increases only slightly. Thus, Zeff increases as we move from left to right across a period. The stronger pull (higher effective nuclear charge) experienced by electrons on the right side of the periodic table draws them closer to the nucleus, making the covalent radii smaller.
Thus, as we would expect, the outermost or valence electrons are easiest to remove because they have the highest energies, are shielded more, and are farthest from the nucleus. As a general rule, when the representative elements form cations, they do so by the loss of the ns or np electrons that were added last in the Aufbau process. The transition elements, on the other hand, lose the ns electrons before they begin to lose the (n – 1)d electrons, even though the ns electrons are added first, according to the Aufbau principle.
Sorting Atomic Radii Predict the order of increasing covalent radius for Ge, Fl, Br, Kr.
Solution Radius increases as we move down a group, so Ge < Fl (Note: Fl is the symbol for flerovium, element 114, NOT fluorine). Radius decreases as we move across a period, so Kr < Br < Ge. Putting the trends together, we obtain Kr < Br < Ge < Fl.
Check Your Learning Give an example of an atom whose size is smaller than fluorine.
Ne or He
Variation in Ionic Radii
Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it is smaller than the atom from which it is derived ((Figure)). For example, the covalent radius of an aluminum atom (1s22s22p63s23p1) is 118 pm, whereas the ionic radius of an Al3+ (1s22s22p6) is 68 pm. As electrons are removed from the outer valence shell, the remaining core electrons occupying smaller shells experience a greater effective nuclear charge Zeff (as discussed) and are drawn even closer to the nucleus.
Cations with larger charges are smaller than cations with smaller charges (e.g., V2+ has an ionic radius of 79 pm, while that of V3+ is 64 pm). Proceeding down the groups of the periodic table, we find that cations of successive elements with the same charge generally have larger radii, corresponding to an increase in the principal quantum number, n.
An anion (negative ion) is formed by the addition of one or more electrons to the valence shell of an atom. This results in a greater repulsion among the electrons and a decrease in Zeff per electron. Both effects (the increased number of electrons and the decreased Zeff) cause the radius of an anion to be larger than that of the parent atom ((Figure)). For example, a sulfur atom ([Ne]3s23p4) has a covalent radius of 104 pm, whereas the ionic radius of the sulfide anion ([Ne]3s23p6) is 170 pm. For consecutive elements proceeding down any group, anions have larger principal quantum numbers and, thus, larger radii.
Atoms and ions that have the same electron configuration are said to be isoelectronic. Examples of isoelectronic species are N3–, O2–, F–, Ne, Na+, Mg2+, and Al3+ (1s22s22p6). Another isoelectronic series is P3–, S2–, Cl–, Ar, K+, Ca2+, and Sc3+ ([Ne]3s23p6). For atoms or ions that are isoelectronic, the number of protons determines the size. The greater the nuclear charge, the smaller the radius in a series of isoelectronic ions and atoms.
Variation in Ionization Energies
The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy (IE1). The first ionization energy for an element, X, is the energy required to form a cation with +1 charge:
The energy required to remove the second most loosely bound electron is called the second ionization energy (IE2).
The energy required to remove the third electron is the third ionization energy, and so on. Energy is always required to remove electrons from atoms or ions, so ionization processes are endothermic and IE values are always positive. For larger atoms, the most loosely bound electron is located farther from the nucleus and so is easier to remove. Thus, as size (atomic radius) increases, the ionization energy should decrease. Relating this logic to what we have just learned about radii, we would expect first ionization energies to decrease down a group and to increase across a period.
(Figure) graphs the relationship between the first ionization energy and the atomic number of several elements. The values of first ionization energy for the elements are given in (Figure). Within a period, the IE1 generally increases with increasing Z. Down a group, the IE1 value generally decreases with increasing Z. There are some systematic deviations from this trend, however. Note that the ionization energy of boron (atomic number 5) is less than that of beryllium (atomic number 4) even though the nuclear charge of boron is greater by one proton. This can be explained because the energy of the subshells increases as l increases, due to penetration and shielding (as discussed previously in this chapter). Within any one shell, the s electrons are lower in energy than the p electrons. This means that an s electron is harder to remove from an atom than a p electron in the same shell. The electron removed during the ionization of beryllium ([He]2s2) is an s electron, whereas the electron removed during the ionization of boron ([He]2s22p1) is a p electron; this results in a lower first ionization energy for boron, even though its nuclear charge is greater by one proton. Thus, we see a small deviation from the predicted trend occurring each time a new subshell begins.
Another deviation occurs as orbitals become more than one-half filled. The first ionization energy for oxygen is slightly less than that for nitrogen, despite the trend in increasing IE1 values across a period. Looking at the orbital diagram of oxygen, we can see that removing one electron will eliminate the electron–electron repulsion caused by pairing the electrons in the 2p orbital and will result in a half-filled orbital (which is energetically favorable). Analogous changes occur in succeeding periods (note the dip for sulfur after phosphorus in (Figure)).
Removing an electron from a cation is more difficult than removing an electron from a neutral atom because of the greater electrostatic attraction to the cation. Likewise, removing an electron from a cation with a higher positive charge is more difficult than removing an electron from an ion with a lower charge. Thus, successive ionization energies for one element always increase. As seen in (Figure), there is a large increase in the ionization energies for each element. This jump corresponds to removal of the core electrons, which are harder to remove than the valence electrons. For example, Sc and Ga both have three valence electrons, so the rapid increase in ionization energy occurs after the third ionization.
| Successive Ionization Energies for Selected Elements (kJ/mol) | |||||||
|---|---|---|---|---|---|---|---|
| Element | IE1 | IE2 | IE3 | IE4 | IE5 | IE6 | IE7 |
| K | 418.8 | 3051.8 | 4419.6 | 5876.9 | 7975.5 | 9590.6 | 11343 |
| Ca | 589.8 | 1145.4 | 4912.4 | 6490.6 | 8153.0 | 10495.7 | 12272.9 |
| Sc | 633.1 | 1235.0 | 2388.7 | 7090.6 | 8842.9 | 10679.0 | 13315.0 |
| Ga | 578.8 | 1979.4 | 2964.6 | 6180 | 8298.7 | 10873.9 | 13594.8 |
| Ge | 762.2 | 1537.5 | 3302.1 | 4410.6 | 9021.4 | Not available | Not available |
| As | 944.5 | 1793.6 | 2735.5 | 4836.8 | 6042.9 | 12311.5 | Not available |
Ranking Ionization Energies Predict the order of increasing energy for the following processes: IE1 for Al, IE1 for Tl, IE2 for Na, IE3 for Al.
Solution Removing the 6p1 electron from Tl is easier than removing the 3p1 electron from Al because the higher n orbital is farther from the nucleus, so IE1(Tl) < IE1(Al). Ionizing the third electron from \(\text{Al}\phantom{\rule{2em}{0ex}}\left({\text{Al}}^{2+}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Al}}^{3+}+{\text{e}}^{\text{−}}\right)\) requires more energy because the cation Al2+ exerts a stronger pull on the electron than the neutral Al atom, so IE1(Al) < IE3(Al). The second ionization energy for sodium removes a core electron, which is a much higher energy process than removing valence electrons. Putting this all together, we obtain: IE1(Tl) < IE1(Al) < IE3(Al) < IE2(Na).
Check Your Learning Which has the lowest value for IE1: O, Po, Pb, or Ba?
Ba
Variation in Electron Affinities
The electron affinity (EA) is the energy change for the process of adding an electron to a gaseous atom to form an anion (negative ion).
This process can be either endothermic or exothermic, depending on the element. The EA of some of the elements is given in (Figure). You can see that many of these elements have negative values of EA, which means that energy is released when the gaseous atom accepts an electron. However, for some elements, energy is required for the atom to become negatively charged and the value of their EA is positive. Just as with ionization energy, subsequent EA values are associated with forming ions with more charge. The second EA is the energy associated with adding an electron to an anion to form a –2 ion, and so on.
As we might predict, it becomes easier to add an electron across a series of atoms as the effective nuclear charge of the atoms increases. We find, as we go from left to right across a period, EAs tend to become more negative. The exceptions found among the elements of group 2 (2A), group 15 (5A), and group 18 (8A) can be understood based on the electronic structure of these groups. The noble gases, group 18 (8A), have a completely filled shell and the incoming electron must be added to a higher n level, which is more difficult to do. Group 2 (2A) has a filled ns subshell, and so the next electron added goes into the higher energy np, so, again, the observed EA value is not as the trend would predict. Finally, group 15 (5A) has a half-filled np subshell and the next electron must be paired with an existing np electron. In all of these cases, the initial relative stability of the electron configuration disrupts the trend in EA.
We also might expect the atom at the top of each group to have the most negative EA; their first ionization potentials suggest that these atoms have the largest effective nuclear charges. However, as we move down a group, we see that the second element in the group most often has the most negative EA. This can be attributed to the small size of the n = 2 shell and the resulting large electron–electron repulsions. For example, chlorine, with an EA value of –348 kJ/mol, has the highest value of any element in the periodic table. The EA of fluorine is –322 kJ/mol. When we add an electron to a fluorine atom to form a fluoride anion (F–), we add an electron to the n = 2 shell. The electron is attracted to the nucleus, but there is also significant repulsion from the other electrons already present in this small valence shell. The chlorine atom has the same electron configuration in the valence shell, but because the entering electron is going into the n = 3 shell, it occupies a considerably larger region of space and the electron–electron repulsions are reduced. The entering electron does not experience as much repulsion and the chlorine atom accepts an additional electron more readily, resulting in a more negative EA.
The properties discussed in this section (size of atoms and ions, effective nuclear charge, ionization energies, and electron affinities) are central to understanding chemical reactivity. For example, because fluorine has an energetically favorable EA and a large energy barrier to ionization (IE), it is much easier to form fluorine anions than cations. Metallic properties including conductivity and malleability (the ability to be formed into sheets) depend on having electrons that can be removed easily. Thus, metallic character increases as we move down a group and decreases across a period in the same trend observed for atomic size because it is easier to remove an electron that is farther away from the nucleus.
Key Concepts and Summary
Electron configurations allow us to understand many periodic trends. Covalent radius increases as we move down a group because the n level (orbital size) increases. Covalent radius mostly decreases as we move left to right across a period because the effective nuclear charge experienced by the electrons increases, and the electrons are pulled in tighter to the nucleus. Anionic radii are larger than the parent atom, while cationic radii are smaller, because the number of valence electrons has changed while the nuclear charge has remained constant. Ionization energy (the energy associated with forming a cation) decreases down a group and mostly increases across a period because it is easier to remove an electron from a larger, higher energy orbital. Electron affinity (the energy associated with forming an anion) is more favorable (exothermic) when electrons are placed into lower energy orbitals, closer to the nucleus. Therefore, electron affinity becomes increasingly negative as we move left to right across the periodic table and decreases as we move down a group. For both IE and electron affinity data, there are exceptions to the trends when dealing with completely filled or half-filled subshells.
Chemistry End of Chapter Exercises
Based on their positions in the periodic table, predict which has the smallest atomic radius: Mg, Sr, Si, Cl, I.
Cl
Based on their positions in the periodic table, predict which has the largest atomic radius: Li, Rb, N, F, I.
Based on their positions in the periodic table, predict which has the largest first ionization energy: Mg, Ba, B, O, Te.
O
Based on their positions in the periodic table, predict which has the smallest first ionization energy: Li, Cs, N, F, I.
Based on their positions in the periodic table, rank the following atoms in order of increasing first ionization energy: F, Li, N, Rb
Rb < Li < N < F
Based on their positions in the periodic table, rank the following atoms in order of increasing first ionization energy: Mg, O, S, Si
Atoms of which group in the periodic table have a valence shell electron configuration of ns2np3?
15 (5A)
Atoms of which group in the periodic table have a valence shell electron configuration of ns2?
Based on their positions in the periodic table, list the following atoms in order of increasing radius: Mg, Ca, Rb, Cs.
Mg < Ca < Rb < Cs
Based on their positions in the periodic table, list the following atoms in order of increasing radius: Sr, Ca, Si, Cl.
Based on their positions in the periodic table, list the following ions in order of increasing radius: K+, Ca2+, Al3+, Si4+.
Si4+ < Al3+ < Ca2+ < K+
List the following ions in order of increasing radius: Li+, Mg2+, Br–, Te2–.
Which atom and/or ion is (are) isoelectronic with Br+: Se2+, Se, As–, Kr, Ga3+, Cl–?
Se, As−
Which of the following atoms and ions is (are) isoelectronic with S2+: Si4+, Cl3+, Ar, As3+, Si, Al3+?
Compare both the numbers of protons and electrons present in each to rank the following ions in order of increasing radius: As3–, Br–, K+, Mg2+.
Mg2+ < K+ < Br– < As3–
Of the five elements Al, Cl, I, Na, Rb, which has the most exothermic reaction? (E represents an atom.) What name is given to the energy for the reaction? Hint: Note the process depicted does not correspond to electron affinity.)
\({\text{E}}^{\text{+}}\left(g\right)+{\text{e}}^{\text{−}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{E}\left(g\right)\)
Of the five elements Sn, Si, Sb, O, Te, which has the most endothermic reaction? (E represents an atom.) What name is given to the energy for the reaction?
\(\text{E}\left(g\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{E}}^{\text{+}}\left(g\right)+{\text{e}}^{-}\)
O, IE1
The ionic radii of the ions S2–, Cl–, and K+ are 184, 181, 138 pm respectively. Explain why these ions have different sizes even though they contain the same number of electrons.
Which main group atom would be expected to have the lowest second ionization energy?
Ra
Explain why Al is a member of group 13 rather than group 3?
Glossary
- covalent radius
- one-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond
- effective nuclear charge
- charge that leads to the Coulomb force exerted by the nucleus on an electron, calculated as the nuclear charge minus shielding
- electron affinity
- energy change associated with addition of an electron to a gaseous atom or ion
- ionization energy
- energy required to remove an electron from a gaseous atom or ion
- isoelectronic
- group of ions or atoms that have identical electron configurations


36 4.1 Principles and Functions of Nonverbal Communication
4.1 Principles and Functions of Nonverbal Communication
Learning Objectives
- Define nonverbal communication.
- Compare and contrast verbal communication and nonverbal communication.
- Discuss the principles of nonverbal communication.
- Provide examples of the functions of nonverbal communication.
As you’ll recall from our introductory chapter, a channel is the sensory route on which a message travels. Oral communication only relies on one channel, because spoken language is transmitted through sound and picked up by our ears. Nonverbal communication, on the other hand, can be taken in by all five of our senses. Since most of our communication relies on visual and auditory channels, those will be the focus of this chapter. But we can also receive messages and generate meaning through touch, taste, and smell. Touch is an especially powerful form of nonverbal communication that we will discuss in this chapter, but we will not get into taste and smell, which have not received as much scholarly attention in relation to nonverbal communication as the other senses. To further define nonverbal communication, we need to distinguish between vocal and verbal aspects of communication. Verbal and nonverbal communication include both vocal and nonvocal elements, and Table 4.1 “Vocal and Nonvocal Elements of Communication”shows the relationship among vocal, nonvocal, verbal, and nonverbal aspects of communication. A vocal element of verbal communication is spoken words—for example, “Come back here.” A vocal element of nonverbal communication is paralanguage, which is the vocalized but not verbal part of a spoken message, such as speaking rate, volume, and pitch. Nonvocal elements of verbal communication include the use of unspoken symbols to convey meaning. Writing and American Sign Language (ASL) are nonvocal examples of verbal communication and are not considered nonverbal communication. Nonvocal elements of nonverbal communication include body language such as gestures, facial expressions, and eye contact. Gestures are nonvocal and nonverbal since most of them do not refer to a specific word like a written or signed symbol does.
| Element | Verbal Communication | Nonverbal Communication |
|---|---|---|
| Vocal | Spoken words | Paralanguage (pitch, volume, speaking rate, etc.) |
| Nonvocal | Writing, sign language | Body language (gestures, facial expressions, eye contact, etc.) |
Source: Adapted from Owen Hargie, Skilled Interpersonal Interaction: Research, Theory, and Practice (London:Routledge, 2011), 45.
Principles of Nonverbal Communication
Nonverbal communication has a distinct history and serves separate evolutionary functions from verbal communication. For example, nonverbal communication is primarily biologically based while verbal communication is primarily culturally based. This is evidenced by the fact that some nonverbal communication has the same meaning across cultures while no verbal communication systems share that same universal recognizability (Andersen, 1999). Nonverbal communication also evolved earlier than verbal communication and served an early and important survival function that helped humans later develop verbal communication. While some of our nonverbal communication abilities, like our sense of smell, lost strength as our verbal capacities increased, other abilities like paralanguage and movement have grown alongside verbal complexity. The fact that nonverbal communication is processed by an older part of our brain makes it more instinctual and involuntary than verbal communication.
Nonverbal Communication Conveys Important Interpersonal and Emotional Messages
You’ve probably heard that more meaning is generated from nonverbal communication than from verbal. Some studies have claimed that 90 percent of our meaning is derived from nonverbal signals, but more recent and reliable findings claim that it is closer to 65 percent (Guerrero & Floyd, 2006). We may rely more on nonverbal signals in situations where verbal and nonverbal messages conflict and in situations where emotional or relational communication is taking place (Hargie, 2011). For example, when someone asks a question and we’re not sure about the “angle” they are taking, we may hone in on nonverbal cues to fill in the meaning. For example, the question “What are you doing tonight?” could mean any number of things, but we could rely on posture, tone of voice, and eye contact to see if the person is just curious, suspicious, or hinting that they would like company for the evening. We also put more weight on nonverbal communication when determining a person’s credibility. For example, if a classmate delivers a speech in class and her verbal content seems well-researched and unbiased, but her nonverbal communication is poor (her voice is monotone, she avoids eye contact, she fidgets), she will likely not be viewed as credible. Conversely, in some situations, verbal communication might carry more meaning than nonverbal. In interactions where information exchange is the focus, at a briefing at work, for example, verbal communication likely accounts for much more of the meaning generated. Despite this exception, a key principle of nonverbal communication is that it often takes on more meaning in interpersonal and/or emotional exchanges.
About 65 percent of the meaning we derive during interactions comes from nonverbal communication.
Nonverbal Communication Is More Involuntary than Verbal
There are some instances in which we verbally communicate involuntarily. These types of exclamations are often verbal responses to a surprising stimulus. For example, we say “owww!” when we stub our toe or scream “stop!” when we see someone heading toward danger. Involuntary nonverbal signals are much more common, and although most nonverbal communication isn’t completely involuntary, it is more below our consciousness than verbal communication and therefore more difficult to control. The involuntary nature of much nonverbal communication makes it more difficult to control or “fake.” For example, although you can consciously smile a little and shake hands with someone when you first see them, it’s difficult to fake that you’re “happy” to meet someone. Nonverbal communication leaks out in ways that expose our underlying thoughts or feelings. Spokespeople, lawyers, or other public representatives who are the “face” of a politician, celebrity, corporation, or organization must learn to control their facial expressions and other nonverbal communication so they can effectively convey the message of their employer or client without having their personal thoughts and feelings leak through. Poker players, therapists, police officers, doctors, teachers, and actors are also in professions that often require them to have more awareness of and control over their nonverbal communication.
 Most people whose careers don’t involve conscious manipulation of nonverbal signals find it difficult to control or suppress them. While we can consciously decide to stop sending verbal messages, our nonverbal communication always has the potential of generating meaning for another person. The teenager who decides to shut out his dad and not communicate with him still sends a message with his “blank” stare (still a facial expression) and lack of movement (still a gesture). In this sense, nonverbal communication is “irrepressible” (Andersen, 1999).
Nonverbal Communication Is More Ambiguous
In Chapter 3 “Verbal Communication”, we learn that the symbolic and abstract nature of language can lead to misunderstandings, but nonverbal communication is even more ambiguous. As with verbal communication, most of our nonverbal signals can be linked to multiple meanings, but unlike words, many nonverbal signals do not have any one specific meaning. If you’ve ever had someone wink at you and didn’t know why, you’ve probably experienced this uncertainty. Did they wink to express their affection for you, their pleasure with something you just did, or because you share some inside knowledge or joke?
Just as we look at context clues in a sentence or paragraph to derive meaning from a particular word, we can look for context clues in various sources of information like the physical environment, other nonverbal signals, or verbal communication to make sense of a particular nonverbal cue. Unlike verbal communication, however, nonverbal communication doesn’t have explicit rules of grammar that bring structure, order, and agreed- on patterns of usage. Instead, we implicitly learn norms of nonverbal communication, which leads to greater variance. In general, we exhibit more idiosyncrasies in our usage of nonverbal communication than we do with verbal communication, which also increases the ambiguity of nonverbal communication.
Nonverbal Communication Is More Credible
Although we can rely on verbal communication to fill in the blanks sometimes left by nonverbal expressions, we often put more trust into what people do over what they say. This is especially true in times of stress or danger when our behaviors become more instinctual and we rely on older systems of thinking and acting that evolved before our ability to speak and write (Andersen, 1999). This innateness creates intuitive feelings about the genuineness of nonverbal communication, and this genuineness relates back to our earlier discussion about the sometimes involuntary and often subconscious nature of nonverbal communication. An example of the innateness of nonverbal signals can be found in children who have been blind since birth but still exhibit the same facial expressions as other children. In short, the involuntary or subconscious nature of nonverbal communication makes it less easy to fake, which makes it seem more honest and credible. We will learn more about the role that nonverbal communication plays in deception later in this chapter.
Functions of Nonverbal Communication
A primary function of nonverbal communication is to convey meaning by reinforcing, substituting for, or contradicting verbal communication. Nonverbal communication is also used to influence others and regulate conversational flow. Perhaps even more important are the ways in which nonverbal communication functions as a central part of relational communication and identity expression.
Nonverbal Communication Conveys Meaning
Nonverbal communication conveys meaning by reinforcing, substituting for, or contradicting verbal communication. As we’ve already learned, verbal and nonverbal communication are two parts of the same system that often work side by side, helping us generate meaning. In terms of reinforcing verbal communication, gestures can help describe a space or shape that another person is unfamiliar with in ways that words alone cannot. Gestures also reinforce basic meaning—for example, pointing to the door when you tell someone to leave. Facial expressions reinforce the emotional states we convey through verbal communication. For example, smiling while telling a funny story better conveys your emotions (Hargie, 2011). Vocal variation can help us emphasize a particular part of a message, which helps reinforce a word or sentence’s meaning. For example, saying “How was your weekend?” conveys a different meaning than “How was your weekend?”
Nonverbal communication can substitute for verbal communication in a variety of ways. Nonverbal communication can convey much meaning when verbal communication isn’t effective because of language barriers. Language barriers are present when a person hasn’t yet learned to speak or loses the ability to speak. For example, babies who have not yet developed language skills make facial expressions, at a few months old, that are similar to those of adults and therefore can generate meaning (Oster, Hegley, & Nagel, 1992). People who have developed language skills but can’t use them because they have temporarily or permanently lost them or because they are using incompatible language codes, like in some cross-cultural encounters, can still communicate nonverbally. Although it’s always a good idea to learn some of the local language when you travel, gestures such as pointing or demonstrating the size or shape of something may suffice in basic interactions.
Nonverbal communication is also useful in a quiet situation where verbal communication would be disturbing; for example, you may use a gesture to signal to a friend that you’re ready to leave the library. Crowded or loud places can also impede verbal communication and lead people to rely more on nonverbal messages. Getting a server or bartender’s attention with a hand gesture is definitely more polite than yelling, “Hey you!” Finally, there are just times when we know it’s better not to say something aloud. If you want to point out a person’s unusual outfit or signal to a friend that you think his or her date is a loser, you’re probably more likely to do that nonverbally. Last, nonverbal communication can convey meaning by contradicting verbal communication. As we learned earlier, we often perceive nonverbal communication to be more credible than verbal communication. This is especially true when we receive mixed messages, or messages in which verbal and nonverbal signals contradict each other. For example, a person may say, “You can’t do anything right!” in a mean tone but follow that up with a wink, which could indicate the person is teasing or joking. Mixed messages lead to uncertainty and confusion on the part of receivers, which leads us to look for more information to try to determine which message is more credible. If we are unable to resolve the discrepancy, we are likely to react negatively and potentially withdraw from the interaction (Hargie, 2011). Persistent mixed messages can lead to relational distress and hurt a person’s credibility in professional settings.
We send mixed messages when our verbal and nonverbal communication contradict each other. If this woman said she was excited about seeing you, would you believe her?
Nonverbal Communication Influences Others
Nonverbal communication can be used to influence people in a variety of ways, but the most common way is through deception. Deception is typically thought of as the intentional act of altering information to influence another person, which means that it extends beyond lying to include concealing, omitting, or exaggerating information. While verbal communication is to blame for the content of the deception, nonverbal communication partners with the language through deceptive acts to be more convincing. Since most of us intuitively believe that nonverbal communication is more credible than verbal communication, we often intentionally try to control our nonverbal communication when we are engaging in deception. Likewise, we try to evaluate other people’s nonverbal communication to determine the veracity of their messages. Students initially seem surprised when we discuss the prevalence of deception, but their surprise diminishes once they realize that deception isn’t always malevolent, mean, or hurtful. Deception obviously has negative connotations, but people engage in deception for many reasons, including to excuse our own mistakes, to be polite to others, or to influence others’ behaviors or perceptions.
The fact that deception served an important evolutionary purpose helps explain its prevalence among humans today. Species that are capable of deception have a higher survival rate. Other animals engage in nonverbal deception that helps them attract mates, hide from predators, and trap prey (Andersen, 1999). To put it bluntly, the better at deception a creature is, the more likely it is to survive. So, over time, the humans that were better liars were the ones that got their genes passed on. But the fact that lying played a part in our survival as a species doesn’t give us a license to lie.
Aside from deception, we can use nonverbal communication to “take the edge off” a critical or unpleasant message in an attempt to influence the reaction of the other person. We can also use eye contact and proximity to get someone to move or leave an area. For example, hungry diners waiting to snag a first-come-first-serve table in a crowded restaurant send messages to the people who have already eaten and paid that it’s time to go. People on competition reality television shows like Survivor and Big Brother play what they’ve come to term a “social game.” The social aspects of the game involve the manipulation of verbal and nonverbal cues to send strategic messages about oneself in an attempt to influence others. Nonverbal cues such as length of conversational turn, volume, posture, touch, eye contact, and choices of clothing and accessories can become part of a player’s social game strategy. Although reality television isn’t a reflection of real life, people still engage in competition and strategically change their communication to influence others, making it important to be aware of how we nonverbally influence others and how they may try to influence us.
Nonverbal Communication Regulates Conversational Flow
Conversational interaction has been likened to a dance, where each person has to make moves and take turns without stepping on the other’s toes. Nonverbal communication helps us regulate our conversations so we don’t end up constantly interrupting each other or waiting in awkward silences between speaker turns. Pitch, which is a part of vocalics, helps us cue others into our conversational intentions. A rising pitch typically indicates a question and a falling pitch indicates the end of a thought or the end of a conversational turn. We can also use a falling pitch to indicate closure, which can be very useful at the end of a speech to signal to the audience that you are finished, which cues the applause and prevents an awkward silence that the speaker ends up filling with “That’s it” or “Thank you.” We also signal our turn is coming to an end by stopping hand gestures and shifting our eye contact to the person who we think will speak next (Hargie, 2011). Conversely, we can “hold the floor” with nonverbal signals even when we’re not exactly sure what we’re going to say next. Repeating a hand gesture or using one or more verbal fillers can extend our turn even though we are not verbally communicating at the moment.
Nonverbal Communication Affects Relationships
To successfully relate to other people, we must possess some skill at encoding and decoding nonverbal communication. The nonverbal messages we send and receive influence our relationships in positive and negative ways and can work to bring people together or push them apart. Nonverbal communication in the form of tie signs, immediacy behaviors, and expressions of emotion are just three of many examples that illustrate how nonverbal communication affects our relationships.
Tie signs are nonverbal cues that communicate intimacy and signal the connection between two people. These relational indicators can be objects such as wedding rings or tattoos that are symbolic of another person or the relationship, actions such as sharing the same drinking glass, or touch behaviors such as hand-holding (Afifi & Johnson, 2005). Touch behaviors are the most frequently studied tie signs and can communicate much about a relationship based on the area being touched, the length of time, and the intensity of the touch. Kisses and hugs, for example, are considered tie signs, but a kiss on the cheek is different from a kiss on the mouth and a full embrace is different from a half embrace. If you consider yourself a “people watcher,” take note of the various tie signs you see people use and what they might say about the relationship.
Immediacy behaviors play a central role in bringing people together and have been identified by some scholars as the most important function of nonverbal communication (Andersen & Andersen, 2005). Immediacy behaviors are verbal and nonverbal behaviors that lessen real or perceived physical and psychological distance between communicators and include things like smiling, nodding, making eye contact, and occasionally engaging in social, polite, or professional touch (Comadena, Hunt, & Simonds, 2007). Immediacy behaviors are a good way of creating rapport, or a friendly and positive connection between people. Skilled nonverbal communicators are more likely to be able to create rapport with others due to attention-getting expressiveness, warm initial greetings, and an ability to get “in tune” with others, which conveys empathy (Riggio, 1992). These skills are important to help initiate and maintain relationships.
While verbal communication is our primary tool for solving problems and providing detailed instructions, nonverbal communication is our primary tool for communicating emotions. This makes sense when we remember that nonverbal communication emerged before verbal communication and was the channel through which we expressed anger, fear, and love for thousands of years of human history (Andersen, 1999). Touch and facial expressions are two primary ways we express emotions nonverbally. Love is a primary emotion that we express nonverbally and that forms the basis of our close relationships. Although no single facial expression for love has been identified, it is expressed through prolonged eye contact, close interpersonal distances, increased touch, and increased time spent together, among other things. Given many people’s limited emotional vocabulary, nonverbal expressions of emotion are central to our relationships.
Nonverbal Communication Expresses Our Identities
Nonverbal communication expresses who we are. Our identities (the groups to which we belong, our cultures, our hobbies and interests, etc.) are conveyed nonverbally through the way we set up our living and working spaces, the clothes we wear, the way we carry ourselves, and the accents and tones of our voices. Our physical bodies give others impressions about who we are, and some of these features are more under our control than others. Height, for example, has been shown to influence how people are treated and perceived in various contexts. Our level of attractiveness also influences our identities and how people perceive us. Although we can temporarily alter our height or looks—for example, with different shoes or different color contact lenses—we can only permanently alter these features using more invasive and costly measures such as cosmetic surgery. We have more control over some other aspects of nonverbal communication in terms of how we communicate our identities. For example, the way we carry and present ourselves through posture, eye contact, and tone of voice can be altered to present ourselves as warm or distant depending on the context.
Aside from our physical body, artifacts, which are the objects and possessions that surround us, also communicate our identities. Examples of artifacts include our clothes, jewelry, and space decorations. In all the previous examples, implicit norms or explicit rules can affect how we nonverbally present ourselves. For example, in a particular workplace it may be a norm (implicit) for people in management positions to dress casually, or it may be a rule (explicit) that different levels of employees wear different uniforms or follow particular dress codes. We can also use nonverbal communication to express identity characteristics that do not match up with who we actually think we are. Through changes to nonverbal signals, a capable person can try to appear helpless, a guilty person can try to appear innocent, or an uninformed person can try to appear credible.
Key Takeaways
- Nonverbal communication is a process of generating meaning using behavior other than words. Nonverbal communication includes vocal elements, which is referred to as paralanguage and includes pitch, volume, and rate, and nonvocal elements, which are usually referred to as body language and includes gestures, facial expressions, and eye contact, among other things.
- Although verbal communication and nonverbal communication work side by side as part of a larger language system, there are some important differences between the two. They are processed by different hemispheres of the brain, nonverbal communication conveys more emotional and affective meaning than does verbal communication, nonverbal communication isn’t governed by an explicit system of rules in the same way that grammar guides verbal communication, and while verbal communication is a uniquely human ability, many creatures including plants, birds, and mammals communicate nonverbally.
- Nonverbal communication operates on the following principles: nonverbal communication typically conveys more meaning than verbal communication, nonverbal communication is more involuntary than verbal communication, nonverbal communication is often more ambiguous than verbal communication, and nonverbal communication is often more credible than verbal communication.
- Nonverbal communication serves several functions.
- Nonverbal communication affects verbal communication in that it can complement, reinforce, substitute, or contradict verbal messages.
- Nonverbal communication influences others, as it is a key component of deception and can be used to assert dominance or to engage in compliance gaining.
- Nonverbal communication regulates conversational flow, as it provides important cues that signal the beginning and end of conversational turns and facilitates the beginning and end of an interaction.
- Nonverbal communication affects relationships, as it is a primary means through which we communicate emotions, establish social bonds, and engage in relational maintenance.
- Nonverbal communication expresses our identities, as who we are is conveyed through the way we set up our living and working spaces, the clothes we wear, our personal presentation, and the tones in our voices.
References
Afifi, W. A. and Michelle L. Johnson, “The Nature and Function of Tie-Signs,” in The Sourcebook of Nonverbal Measures: Going beyond Words, ed. Valerie Manusov (Mahwah, NJ: Lawrence Erlbaum, 2005): 190.
Andersen, P. A., Nonverbal Communication: Forms and Functions (Mountain View, CA: Mayfield, 1999), 17.
Andersen, P. A. and Janis F. Andersen, “Measures of Perceived Nonverbal Immediacy,” in The Sourcebook of Nonverbal Measures: Going beyond Words, ed. Valerie Manusov (Mahwah, NJ: Lawrence Erlbaum, 2005): 113–26.
Comadena, M. E., Stephen K. Hunt, and Cheri J. Simonds, “The Effects of Teacher Clarity, Nonverbal Immediacy, and Caring on Student Motivation, Affective and Cognitive Learning,” Communication Research Reports 24, no. 3 (2007): 241.
Hargie, O., Skilled Interpersonal Interaction: Research, Theory, and Practice, 5th ed. (London: Routledge, 2011), 47.
Guerrero, L. K. and Kory Floyd, Nonverbal Communication in Close Relationships (Mahwah, NJ: Lawrence Erlbaum, 2006): 2.
Oster, H., Douglas Hegley, and Linda Nagel, “Adult Judgments and Fine-Grained Analysis of Infant Facial Expressions: Testing the Validity of A Priori Coding Formulas,” Developmental Psychology 28, no. 6 (1992): 1115–31.
Richmond, V. P., Derek R. Lane, and James C. McCroskey, “Teacher Immediacy and the Teacher-Student Relationship,” in Handbook of Instructional Communication: Rhetorical and Relational Perspectives, eds. Timothy P. Mottet, Virginia P. Richmond, and James C. McCroskey (Boston, MA: Pearson, 2006), 168.
Riggio, R. E., “Social Interaction Skills and Nonverbal Behavior,” in Applications of Nonverbal Behavior Theories and Research, ed. Robert S. Feldman (Hillsdale, NJ: Lawrence Erlbaum, 1992), 12.