Seeing and Perceiving最新文献

Exposure to synchronous but spatially discordant auditory and visual inputs produces adaptive recalibration of the respective localization processes, which manifest themselves in measurable aftereffects. Here we report two experiments that examined the time course of visual recalibration of apparent sound location in order to establish the build-up and dissipation of recalibration. In Experiment 1 participants performed a sound localization task before and during exposure to an auditory-visual discrepancy. In Experiment 2, participants performed a sound localization task before and after 60, 180 or 300 exposures to the discrepancy and aftereffects were measured across a series of post-adaptation sound localization trials. The results show that recalibration is very fast. Substantial aftereffects are obtained after only 18-24 exposures and asymptote appears to be reached between 60 and 180 exposures. The rate of adaptation was independent of the size of the discrepancy. The retention of the aftereffect was strong, as we found no dissipation, not even after as few as 60 exposure trials.

Drawing on many seemingly disparate and unrelated lines of evidence, we argue that the direction of the simultaneous contrast effect in three-dimensional colour space is given by the difference vector between target and surround ('direction hypothesis'). This challenges the traditional idea according to which the direction of the simultaneous contrast effect is complementary to the colour of the surround ('complementarity law'). We also argue that the size of the simultaneous contrast effect is either constant or decreases with the difference between target and surround in three-dimensional colour space. The latter proposal challenges Kirschmann's fourth law. Within our theoretical framework, the universally presumed validity of the complementarity law and Kirschmann's fourth law can be understood as resulting from the failure to take various confounding factors into account when interpreting empirical data, the most prominent of which is the influence of temporal von Kries adaptation.

Numerous studies have demonstrated that sighted and blind individuals find it difficult to recognize tactile pictures of common objects. However, it is still not clear what makes recognition of tactile pictures so difficult. One possibility is that observers have difficulty acquiring the global shape of the image when feeling it. Alternatively, observers may have an accurate understanding of the shape but are unable to link it to a particular object representation. We, therefore, conducted two experiments to determine where tactile picture recognition goes awry. In Experiment 1, we found that recognition of tactile pictures by blindfolded sighted observers correlated with image characteristics that affect shape acquisition (symmetry and complexity). In Experiment 2, we asked drawing experts to draw what they perceived after feeling the images. We found that the experts produced three types of drawings when they could not recognize the tactile pictures: (1) drawings that did not look like objects (incoherent), (2) drawings that looked like incorrect objects (coherent but inaccurate) and (3) drawings that looked like the correct objects ( coherent and accurate). The majority of errors seemed to result from inaccurate perception of the global shape of the image (error types 1 and 2). Our results suggest that recognition of simplistic tactile pictures of objects is largely inhibited by low-level tactile shape processing rather than high-level object recognition mechanisms.