Abstract
Retinal inputs that are perceptually suppressed can still build up to various aftereffects such as linear motion or orientation. However, in a previous study we found that the identity-specific face aftereffect following 4 s of adaptation is effectively cancelled by withdrawing attention from the adapting stimulus. Here, we examined whether 1) attention is necessary for gradual buildup of face-identity aftereffect over many trials, 2) adaptation to emotional expressions is modulated by attention, and 3) attentional manipulation has any effect on conscious face identification. In Exp 1, an anti-face image was displayed for 10s (initial adaptation), and redisplayed for 1 s between trials (readaptation). At the same time, a stream of digits (3Hz) was displayed at fovea. Observers (n=9) were instructed to either attend to the distracting digits and report occurrences of letters, or ignore them. A test image followed and was identified by pressing a key. The identity strength of the test face varied between 0 (average) and 0.4. When the distracting stimuli were ignored, there was significant shift in the identification curve as a function of identity strength (p < .01). The aftereffect disappeared completely when subjects monitored the digits. In Exp 2, happy and angry expressions were tested on 5 observers. The paradigm was similar to Exp 1. Although when the distracters were attended, adaptation to emotion was reduced (p < .05), some aftereffect specific to the emotional expression still remained (p < .05). In Exp 3, observers concurrently performed both digit/letter and face identification tasks. Surprisingly, the shift in the identification curve due to inattention was negligible. We conclude that the implicit processing of face identity and emotion underlying the corresponding aftereffects require different levels of selective attention. Adaptation to emotion is possible in near absence of attention. Explicit face identification (Exp 3) also seems to be robust to attentional blink.
We wish to thank Gopal Sarma for assisting in Exp 1 and 3, and Joel Gutierrez for Exp 2.