PERCEPTION ACTION COGNITION TALK
Thursday March 20th 2014, 1:00pm
PERCEPTION OF HUMAN AND ANIMAL BODIES
Perception of the human body is special because it is very familiar to view and also because it is similar to an observer’s own body. We conducted a series of experiments to investigate the effects of biomechanical constraints (possible or impossible postures) on perception of the human body. In a first experiment we showed that it is more difficult to recognize impossible postures and actions than possible postures and actions. These results suggest that our brain uses some knowledge of biomechanical constraints to perceive the human body. Next, we investigated the difference between the perception of human and animal bodies. Human observers could discriminate actual animal biological motions from human mimicry of those motions, but performance decreased with inversion. Thus, the perceptual system for perceiving animal bodies is partly identical to that for perceiving human bodies.
PRESENTED BY
Michiteru Kitazaki
Professor
from the Toyohashi University of Technology
INVITED BY
Frank E. Pollick

1:30pm: ESTIMATING THE “AVERAGE RACE” IN A DYNAMIC CROWD OF FACES
Inspired by recent studies of “ensemble” face processing, we asked whether observers could accurately estimate the ethnic composition of an array of faces. We also examined whether such estimates were influenced by the race of the observer. We developed a new task in which a set of 16 faces was continuously shuffled within a moving 4 x 4 grid. This design prevents explicit estimation and blocks spatial sub-sampling. Across trials we systematically varied the proportion of Asian and Caucasian faces. Two groups of observers were assigned different target and distractor races. Their task was to indicate whether there were more targets or distractors present on each trial. Each group consisted of 8 Asian and 8 Caucasian observers. We fitted cumulative normal functions to the response distributions and extracted the PSE and JND as dependent measures. The same 2 (Observer Race) x 2 (Target Race) ANOVA was used for analysis. For PSE, there were main effects of Observer and Target that did not interact. Observers consistently weighted other-race faces more heavily than own-race faces and PSEs were generally shifted in the direction of the Target. For JND, there was a main effect of Observer and a Observer x Target interaction. While Asian observers were generally more sensitive, both groups had smaller JNDs when the target was the other-race. Overall, our findings indicate that observers can rapidly estimate the racial composition of a group of faces, but these estimates are influenced by their own race.
PRESENTED BY
Ian Thornton
Professor
from the University of Malta
INVITED BY
Frank E. Pollick