Robin S.S. Kramer, James E. King, Robert Ward Presented by: Maeghyn Koehler and Char May Schule

Identifying personality from the static, nonexpressive face in humans and chimpanzees: evidence of a shared system for signaling personality Robin S.S. Kramer, James E. King, Robert Ward Presented by: Maeghyn Koehler and Char May Schule

Background • "Personality traits describe the stable context-general behavioral biases of an individuals" • It had been shown there is a genetic heritability to personality • Humans show cross-cultural and cross-species generalization of personality factors • Socially relevant personality traits can be identified by static non-expressive faces • It is believed that our signal system is evolutionary therefore we will share some traits with other primates • Dominance is expressed by extroversion in humans

Stimuli • Started with set of 37 photos from previous study • Chose photos: • Looking straight on • Had no facial expression • Were cropped to only the head and neck • 15 characteristics were chosen • Highest and lowest rating of each chosen

Study 1 Methods • Participants were presented with a high-low pair of a characteristic and asked to choose the face that best fit the on screen definition of a personality trait • After the participants were asked to rate 1 (young) to 5 (old) the age of the chimpanzees • Participants also completed a task of humans of the same task

Study 1 Results and Discussion • Accurate perception of "dominant" and "active" characteristics. • Close to significant accurary on "sympathetic." • Poor perception of "sociable." • Accurate estimate of chimp's age. Characteristics relating to extraversion, and possibly agreeableness, were accuratly perceived in chimpanzee faces.

Class Discussion Why do you think participants were able to accurately identify traits of "dominance" and "active" but not the charatertic of "sociable"?

Study 2 Methods • Saw a single image of a chimpanzee at a time and asked to rate 1 (very low) to 7 (very high) on the defined characteristic • Participants also completed the same task with human faces

Study 2 Results and Discussion • Ratings of dominance significantly correlated with actual dominance. • No significance correlations for other characteristics. • Accuracy of dominance ratings was not affected by age-related cues. • No significant difference in perception of dominance of males and females. The characteristic of dominance was accurately assessed even though participants were unable to compare the faces associated with extreme personality values.

Study 3 Methods • Participants were presented a high-low pair of chimpanzees and asked to select the more dominant • Each pair was of the same sex

Study 3 Results and Discussion • Significantly accurate perception of dominance for within-sex comparisons of males and females. • More accuracy on perception of dominance in males than females. Dominance accurary was present for both males and females.

Study 4 Methods • Two blocks were presented: one chimpanzee and one human • In the chimpanzee block, high-low pairs of photos were presented and they were asked to identify the more dominant individual • In the human block, high-low pairs of photos were presented and they were asked to identify the more extroverted individual

Study 4 Results and Discussion • Significant accuracy of chimp dominance. • Significant accuracy of human extraversion. • However, there were individual differences in performace on tasks. Particiapant scores on the "social skills" domain of the AQ were negatively correlated with accuracy on human discription task but not on chimp task.

Class Discussion Why do you think participants with higher scores on Autism had trouble identifying human characteristics but not with identifying chimpanzee characteristics?

General Discussion The results demonstrate that humans can accurately perceive charactersitics relating to extraversion in chimpanzee faces on the basis of static, nonexpressive cues. Also, people can use cues in human and chimp faces to identify those who are biased toward social activity and dominace-related behaviors.

General Discussion The researchers hypothsize a shared signal for personality from the face in humans and chimpanzees on the basis of shared evolutionary past. Humans and chimps evolved to share aspects of a system for communicating behavioral biases to conspecifics. This shared system would involve shared aspects for personality, shared links between personality and facial morphology and shared cognitive mechanisms for processing those links.

Confounds and Limitations • Culture and/or personality of participant may affect participant performance. • Although the results demonstrate that people can indentify links between personality and facial morphology in humans and chimps, it is not known wether chimps have similar abilities to process and use these signals. Do you think the researchers are right to assume that chimps also have this ability? How could we test chimpanzee ability to identify personality traits?

Class Discussion • What are the benefits for the signal sender in this arrangement? • Why do you think humans are better at identifying traits of extraversion and dominance than traits like sociable, active or sympathetic? What's the advantage of being able to identify these traits but not others?

Robin S.S. Kramer, James E. King, Robert Ward Presented by: Maeghyn Koehler and Char May Schule