Abstract
Holistic processing (HP) for faces (and objects of expertise) can be measured in a sequential matching task with two composite images (S1 and S2), when subjects try to selectively attend to one part of the composites (e.g., the top) and ignore the other part. HP is evidenced by a congruency effect between the correct responses on the attended and irrelevant parts. Last year, we reported that misaligning parts of a face composite at encoding did not substantially reduce HP, suggesting that the locus of this effect is not at encoding (Gauthier et al., VSS 2003). Here we investigate the possibility that selective attention during the perceptual judgment is the locus of HP. High perceptual load can facilitate selective attention and reduce the processing of irrelevant distractors (e.g., Lavie, 1995; Yi et al., 2004). We ask if a high perceptual load would increase selective attention to a face part (in other words decrease HP), especially with a load during the matching judgment. We increased perceptual load by adding Gaussian noise to the attended top half of the composites. In a sequential matching task where subjects matched the top of two composites, S1 and S2, the noise was either added to S1, S2 or both S1 and S2. Compared to a control (no noise) condition, perceptual load significantly impaired overall performance, without impacting the magnitude of HP in sensitivity. More importantly, perceptual load increased HP in reaction times, but only when added to S2. These results are consistent with prior findings that HP is more influenced by manipulations at test than at encoding. However, contrary to its influence in studies where attended and irrelevant information are different objects, perceptual load increased rather than decreased distractor processing. This suggests that the relationship between perceptual load and selective attention depends on the nature of the load and the relationship between attended and irrelevant information.