The experiments reported by Snodgrass, Shevrin, and Kopka appear to demonstrate that words are perceived even when overall forced-choice discrimination performance does not deviate from chance. We replicated their critical finding in two separate experiments; our results indicated that the subjects′ preferences for one of the two strategy conditions predicted significant deviations from chance performance in the pop condition, even though the overall performance in this condition did not differ from chance. In addition, we found that task preference had no (...) effect when blank cards rather than words were presented and that the words could not be detected when subjects were simply asked to decide on each trial whether a stimulus had been presented. These results suggest that it is possible to demonstrate perception below an objective threshold defined in terms of overall discrimination performance. As such, the results highlight the importance of considering individual differences in studies of perception without awareness. (shrink)

Perceptual tasks such as object matching, mammogram interpretation, mental rotation, and satellite imagery change detection often require the assignment of correspondences to fuse information across views. We apply techniques developed for machine translation to the gaze data recorded from a complex perceptual matching task modeled after fingerprint examinations. The gaze data provide temporal sequences that the machine translation algorithm uses to estimate the subjects' assumptions of corresponding regions. Our results show that experts and novices have similar surface behavior, such as (...) the number of fixations made or the duration of fixations. However, the approach applied to data from experts is able to identify more corresponding areas between two prints. The fixations that are associated with clusters that map with high probability to corresponding locations on the other print are likely to have greater utility in a visual matching task. These techniques address a fundamental problem in eye tracking research with perceptual matching tasks: Given that the eyes always point somewhere, which fixations are the most informative and therefore are likely to be relevant for the comparison task? (shrink)