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Z94.9 Human Factors (Ergonomics) Engineering



LANDOLT RING. A ring with a small gap at one point, used to test visual acuity by having observer report orientation of the gap.

LATERAL. Of or pertaining to the side or lateral axis; directed, moving or located along, or parallel to, the lateral axis.

LEARNING. A relatively permanent change in personality (including cognitive, affective, attitudinal, motivational, behavioral, experiential, and the like),  reflecting a change in performance usually brought about by practice although it may arise from insight or other factors, including memory.

LEARNING CURVE. A function indicating learning rate. When graphed, typically time or practice trial is plotted on the abscissa and a performance measure is plotted on the ordinate.

LEARNING, TRIAL-AND-ERROR. The process in which a person or animal, having no already established response to the requirements of the task, responds at first to only the task’s general features with a wide variety of acts, then gradually eliminates the responses that prove unsatisfactory and repeats with increasing frequency those that prove satisfactory.

LEARNING, WHOLE VS. PART. In “whole learning,” all of the material to be learned is worked through in successive repetitions from first to last; in “part learning” (or “piecemeal learning”), the material is broken into smaller segments to be learned separately and then combined into the whole.

LIFE SUPPORT. An area of human factors which focuses on health promotion, biomedical aspects of safety, protection, sustenance, escape, survival, and recovery of personnel.

LIGHT ADAPTATION. A process of neuro-chemical changes whereby the visual system becomes less sensitive to light.

LIGHT FLUX. Rate at which a source emits light energy (evaluated in terms of visual effect) and expressed in lumens (lm) (q.v.).

LIGHT PEN. An input device shaped like a pen which emits energy to a particular location on a light sensitive display.

LIKERT SCALE. An ordinal rating scale, typically consisting of 5 or 7 items, labelled from strongly agree to strongly disagree.

LIMEN. Threshold; a psychophysical concept denoting the lowest detectable intensity of any sensory stimulus.

LINK ANALYSIS. An analysis of the visual, auditory, and tactual links between human and machine or between one human and another involved in an operation. Primary objectives are determination of the importance of links, frequency of their use, and their adequacy.

LOAD. The demand made by inputs on performance.

LOAD, SENSORY. The number and variety of stimuli to which responses must be made. For example, if the operator must discriminate among several different classes of visual stimuli, the load on the visual system is greater than if discrimination is of only one type or of limited types.

LOCALIZATION, AUDITORY. The capability of an observer to identify the position of a sound source with reference to himself.

LOUDNESS. The attribute of auditory sensation by which sounds may be ordered on a scale extending from soft to loud. The unit of loudness is the sone. Often a weighting network is used to determine loudness (i.e. a weighted scale for noise measurement).

LOUDNESS CONTOUR. A graph of sound pressure level versus frequency, showing the sensitivity of the ear.

LOUDNESS LEVEL. The (judged) loudness level of a sound, in phons, is numerically equal to the median sound pressure level, in decibels relative to 20 micronewtons per square meter, of a 1000 hertz reference tone presented to subjects facing the sound source and judged by the subjects in a number of trials to be as loud as the sound under test.

LUMINOUS FLUX. The total visible energy emitted by a source per unit of time is called the “total luminous flux from the source.” The unit of flux, the LUMEN (lm) is the flux emitted in a unit solid angle (steradian) by a point source of one candela luminous intensity. A uniform point source of one candela intensity thus emits 4  lumens.


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