Different Spatial Frequency Tuning for Judgments of Eye Gaze and Facial Identity
33.558, Sunday, 18-May, 8:30 am - 12:30 pm, Pavilion
Mark Vida1, Daphne Maurer1; 1Department of Psychology, Neuroscience & Behaviour, McMaster University
Humans use the direction of people's gaze as a cue to their mental and emotional states. Human adults are most efficient in using low (coarse details) to mid (finer details) spatial frequencies to discriminate facial identities (Gao & Maurer, 2011). Adults are highly sensitive to changes in the direction of gaze (Vida & Maurer, 2012a). Here we tested whether adults’ sensitivity to eye gaze, like their sensitivity to identity, is tuned to a limited range of spatial frequencies. In Experiment 1, participants (n=4) viewed faces presented with filtered noise that masked one of 10 narrow spatial frequency bands, with the centre frequency of the noise varying between blocks. Participants discriminated between two male faces or two female faces, or between gaze shifted to the left or right by 4.8º or 8º. We measured participants' contrast thresholds for each task, and used an ideal observer analysis to evaluate the importance of each frequency band for human sensitivity, taking into account the amount of information available to perform the task. For judgments of identity, participants relied on low to mid frequencies, but not on higher frequencies, a pattern consistent with previous studies (Gao & Maurer, 2011). For eye gaze, a small range of mid to high frequencies was most important, and the highest frequency important for gaze was higher than that for identity. In Experiment 2, participants (n=6) discriminated among horizontal and among vertical shifts of gaze. The most important frequencies were the same as for judgments of gaze in Experiment 1. However, the surrounding frequencies were less important for horizontal than vertical judgments, a result that may reflect finer tuning for horizontal judgments. Together, these results provide the first evidence that sensitivity to gaze is tuned to higher spatial frequencies than sensitivity to facial identity.