Abstract
In a recent study, we used the Bubbles technique (Gosselin & Schyns, 2001) to probe the facial features that lead to changes in the perceived trustworthiness of a face (Robinson et al., 2014). However, this study did not allow us to identify which facial features are involved in accurate trustworthiness judgments. Surprisingly, few studies have investigated whether the diagnostic facial information for trustworthiness judgment is stable across faces from different ethnicities. The present study aims to pinpoint the diagnostic facial features for accurate trustworthiness judgments of Caucasian (Cau) and African-american (AA) faces using Bubbles. First, 40 participants rated the level of trustworthiness of a large number of faces from both races. These judgments were then used as our accuracy measure in a Bubbles experiment, conducted on another group of 50 participants. On each trial, two bubblized faces were shown to the participants and they were asked to choose the one that appeared most trustworthy. The bubbles’ locations were the same on both faces. The average accuracy for each face ethnicity was maintained at 62.5% (approximately halfway between chance and the average performance without Bubbles) by adjusting the number of bubbles on a trial-to-trial basis using QUEST (Watson & Pelli, 1983). A paired t-test indicated that participants needed less bubbles with Cau faces (M=67.4, SD=40.2) than with AA faces (M=90.6, SD=43.7), t(49)=-2.86, p=0.006. We computed distinct classification images for both ethnicities by calculating a weighted sum of the bubbles mask, using the accuracy transformed into z-scores as weights. A cluster test (Chauvin et al., 2005) was applied on the classification images to determine statistical significance. Our results indicate that the left eye is positively correlated with accurate trustworthiness judgments for Cau faces, while the area of the mouth and the right eye are diagnostic for AA faces.
Meeting abstract presented at VSS 2015