text: Reactions to unresponsive examples of these figures were studied in Edward Tronick's still-face experiments.
full_question: Reactions to unresponsive examples of these figures were studied in Edward Tronick's still-face experiments. One of these figures is moved into and out of a room in Mary Ainsworth's "strange situation" procedure. An experiment found that a drumming toy bear elicited a higher emotionality score in animals in the absence of one of these figures. One scientist discovered that mallards will treat farmyard ducks, but not muscovy ducks, as one of these. Due to "contact comfort," cloth is more effective than wire mesh for creating replacements of them for rhesus macaques. Konrad Lorenz found that, in the critical period, greylag goslings can become attached to a substitute for one via imprinting. For 10 points, name these relatives, which Harry Harlow's experiments replaced with milk-dispensing surrogates.
first_sentence: Reactions to unresponsive examples of these figures were studied in Edward Tronick's still-face experiments.
raw_answer: mothers [or parents; accept surrogate mothers or surrogate parents before "surrogates" is read]