The importance of pigmentation for face recognition

Holistic Face Processing is Induced by Shape and Texture

There is increasing evidence that shape and texture are integral parts of face identity. However, it is less clear whether face-specific processing mechanisms are triggered by face shape alone, or if texture might play an important role. We address this question by studying mechanisms involved in holistic face processing. Face stimuli were either full-color pictures of real faces (shape and texture) or line drawings of the same faces (shape without texture). In a change detection task subjects judged whether eyes and eyebrows in two otherwise identical, sequentially presented faces were different in size or not. Afterwards, subjects had to identify the just presented face among two distractor faces (forced-choice identification task). The results obtained from the two tasks give rise to the conclusion that face identification and change detection tasks engage different processing strategies, which capture different aspects of holistic processing. Real faces were processed holistically, irrespective of task requirements, whereas line drawings were processed holistically only if face identification was required. On the basis of the data we conclude that face shape is relevant for the initial processing stage and feature binding, whereas face texture seems to be involved in processing of face configuration more specifically. Moreover, results demonstrate considerable flexibility of the face processing systems allowing for goal-directed and task-specific recall of face information.

Attention to Form or Surface Properties Modulates Different Regions of Human Occipitotemporal Cortex

We carried out 2 functional magnetic resonance imaging experiments to investigate the cortical mechanisms underlying the contribution of form and surface properties to object recognition. In experiment 1, participants performed same-different judgments in separate blocks of trials on pairs of unfamiliar "nonsense" objects on the basis of their form, surface properties (i.e., both color and texture), or orientation. Attention to form activated the lateral occipital (LO) area, whereas attention to surface properties activated the collateral sulcus (CoS) and the inferior occipital gyrus (IOG). In experiment 2, participants were required to make same-different judgments on the basis of texture, color, or form. Again attention to form activated area LO, whereas attention to texture activated regions in the IOG and the CoS, as well as regions in the lingual sulcus and the inferior temporal sulcus. Within these last 4 regions, activation associated with texture was higher than activation associated with color. No color-specific cortical areas were identified in these regions, although parts of V1 and the cuneus yielded higher activation for color as opposed to texture. These results suggest that there are separate form and surface-property pathways in extrastriate cortex. The extraction of information about an object's color seems to occur relatively early in visual analysis as compared with the extraction of surface texture, perhaps because the latter requires more complex computations.