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There has been much debate on whether color categories affect how we perceive color. Recent theories have put emphasis on the role of top-down influence on color perception that the original continuous color space in the visual cortex may be transformed into categorical encoding due to top-down modulation. To test the influence of color categories on color perception, we adopted an RSVP paradigm, where color stimuli were presented at a fast speed of 100 ms per stimulus and were forward and backward masked by the preceding and following stimuli. Moreover, no explicit color naming or categorization was required. In theory, backward masking with such a short interval in a passive viewing task should constrain top-down influence from higher-level brain areas. To measure any potentially subtle differences in brain response elicited by different color categories, we embedded a sensitive frequency-tagging-based EEG paradigm within the RSVP stimuli stream where the oddball color stimuli were encoded with a different frequency from the base color stimuli. We showed that EEG responses to cross-category oddball colors at the frequency where the oddball stimuli were presented was significantly larger than the responses to within-category oddball colors. Our study suggested that the visual cortex can automatically and implicitly encode color categories when color stimuli are presented rapidly. [ABSTRACT FROM AUTHOR]

Highlights: [•] Adults implicitly learn the prototype and first two eigenfaces of the studied faces. [•] The prototype and eigenfaces are learned more efficiently than the studied faces. [•] The learning of the eigenfaces is as strong as the prototype learning. [ABSTRACT FROM AUTHOR]

Abstract: We measured contrast thresholds for the identification of faces and facial expressions as a function of the center spatial frequency of narrow-band additive noise. In adults, masking of mid spatial frequencies (11–16c/fw) caused the largest elevation in contrast threshold (Experiment 1). Ideal observer analysis revealed that adults were equally sensitive to available information at low and mid spatial frequencies, both of which they used more efficiently than high spatial frequencies. The drop-off of sensitivity at high spatial frequencies began at a lower spatial frequency for recognizing facial identity than for recognizing facial expression. As a result, the critical band was higher for expression than for identity. The critical band for both identity and expression shifted to slightly lower values as distance increased (Experiment 2), a pattern indicating only partial scale invariance. Children aged 10 and 14years showed similar tuning but needed more contrast (Experiment 3). The patterns suggest that adults use finer details for recognizing facial expressions than for identifying faces, a tuning that appears as early as age 10. [Copyright &y& Elsevier]