Awareness and confidence ratings in motion perception without geniculo-striate projection.
Sahraie A., Weiskrantz L., Barbur JL.
We have previously reported that under certain experimental conditions, a subject with damaged primary visual cortex performed significantly above chance in discriminating motion direction and orientation either with or without awareness of the stimulus presentation in his blind hemifield. The subject's performance varied as a function of stimulus speed, excursion length, and background luminance. Present observations confirm the previous findings of above chance discrimination scores both with and without awareness, but nevertheless indicate an overall increase in sensitivity over the past 2 years. In addition to discriminating the direction of motion, the subject was asked on every trial to report either awareness or confidence or both, on a six-point scale. The results show that the introduction of a six-point scale for the reported level of awareness yielded similar results to those when the subject was given a binary choice to indicate the presence or absence of conscious awareness. The area under the receiver operating characteristic (ROC) curves obtained from the rating data was used to compare results across different experimental conditions. It was found that although the subject's reported confidence and awareness varied monotonically as a function of stimulus speed, they were not equivalent measures.