Information Attracts Attention: A Probabilistic Account of the Cross-Race Advantage in Visual Search

Information Attracts Attention: A Probabilistic Account of the Cross-Race Advantage in Visual Search Zhang Lingyun Matthew H. Tong Garrison W. Cottrell ( lingyun, mhtong, gary@ucsd.edu) Department of Computer Science and Engineering University of California, San Diego 9500 Gilman Drive La Jolla, CA 92037 USA Abstract lected for identifying individuals that a person comes in con- tact with. As people are generally more exposed to faces from their own race, the features developed are tuned accordingly and are thus less optimal for faces from other races. This hypothesis has been computationally modelled using princi- pal component analysis, which successfully accounts for the other-race effect. (O’Toole, Deffenbacher, Abdi, & Bartlett, 1991; O’Toole, Deffenbacher, Valentin, & Abdi, 1994). On the other hand, Levin found that people who show the other-race effect are faster in searching for a cross-race (CR) face among same-race (SR) faces than searching for an SR faces among CR faces (Levin, 1996, 2000). Figure 1 shows an example stimulus from his experiment. In this stimulus, there is one African face (the bottom one) and seven images of a Caucasian face. The faces were preprocessed to have identical shading, hair, ears and jaw lines. The only differ- ence between faces from different races are thus the internal features (e.g. eyes, mouth, and nose). The subjects’ task is to detect whether the target face, i.e. the African face in this stimulus, is present or not. For a Caucasian subject, this re- quires looking for a CR face in SR faces. People are better at recognizing faces from their own race than from different races (Shapiro & Penrod, 1986; Bothwell, Brigham, & Malpass, 1989), an effect commonly known as the other-race effect. The causes of this effect have been attributed to the fact that people have more experience with faces from their own race during development (Feingold, 1914; Chance, Turner, & Goldstein, 1982; Shepard, 1981; Valentine, Chiroro, & Dixon, 1995). However, in visual search tasks, cross-race (CR) faces are found faster than same-race (SR) faces (Levin, 1996, 2000). This advantage of CR faces in visual search tasks seems at first to be inconsistent with the advantage of the SR face in recognition tasks. To account for this discrep- ancy, Levin proposed that there is a race feature, which is ac- tive only for CR faces. By explicitly assuming this feature, the face search data fits into a visual search paradigm in which the search asymmetry can be explained. In this paper, we will present an alternate explanation of the CR face advantage in vi- sual search which is consistent with the SR face advantage in recognition without making additional assumptions. The prob- abilistic visual search model we developed predicts that CR faces should be found faster than SR faces, given that people have more experience with SR faces. This model was devel- oped based on an intuitive assumption of the goal of the visual system, yet, with no extra assumptions, it fully accounts for the CR advantage based on the same mechanism believed to be responsible for the SR advantage in recognition. Keywords: visual search; other race effect; search asymmetry; saliency; self-information Introduction People are better at recognizing faces from their own race than from different races (Shapiro & Penrod, 1986; Bothwell et al., 1989). This is known as the other-race effect, cross race effect or own race bias. Most researchers agree that this phenomenon is caused by the learning history; the fact that people have more experience with their own race faces dur- ing development results in more accurate recognition. As mi- norities usually do not have an other race effect for the major- ity, it might be more appropriate called an unfamiliar facial structure effect. It was reported that while six year old chil- dren did not show a significant other-race effect, older partic- ipants show a degree of the effect positively correlated with age (Chance et al., 1982). Feingold suggested that the degree of the other-race effect a person shows is dependent on how much contact he has with people from other races (Feingold, 1914). Later studies argued that contact for individuation is more important than mere contact (Shepard, 1981; Valentine et al., 1995). This leads to the hypothesis of optimal feature selection. The key idea is that an optimal feature set is se- Figure 1: A sample stimulus in the visual search task. The target in this stimulus is an African face (the bottom one). The rest, i.e. the distractors, are Caucasian faces. Levin’s finding, referred to as the advantage of CR faces in visual search, seems to be in conflict with the decreased accu- racy of CR faces in recognition; it is counterintuitive that ex-