J Exp Psychol Anim Behav Process 5:211–223īruce C (1982) Face recognition by monkeys: absence of an inversion effect. J Exp Psychol Hum Percept Perform 31:20–39īlough DS (1979) Effects of the number and form of stimuli on visual search in the pigeon. The results clearly show that the configuration of facial features plays a critical role in the upright superiority effect, and strongly suggest similarity in face processing in humans and chimpanzees.īallaz C, Boutsen L, Peyrin C, Humphreys GW, Marendaz C (2005) Visual search for object orientation can be modulated by canonical orientation. To examine this possibility, various stimuli manipulations were introduced in subsequent experiments. Thus, the configural properties of facial features, which cause an inversion effect in face recognition in humans and chimpanzees, were thought to be a source of the upright superiority effect in the visual search process.

Upright superiority was shown in a visual search for orientation when caricaturized human faces and dog faces were used as stimuli for the chimpanzee but not when shapes of a hand and chairs were presented. The present study sought to extend these results and explore factors affecting the face-specific upright superiority effect. This upright superiority effect was also seen when using chimpanzee faces as targets but not when using photographs of a house. A previous experiment showed that a chimpanzee performed better in searching for a target human face that differed in orientation from distractors when the target had an upright orientation than when targets had inverted or horizontal orientation.

Chimpanzee face side view