Abstract
When we asked observers to perform a discrimination task with stimuli that were either geometrically organized in order to produce a subjective shape or disorganized in order to provide only local stimulus information, observers casually reported that the organized stimulus appeared to persist longer than the misaligned one.
Therefore in the current experiment we tested the question whether the apparent duration of a visual stimulus is affected by its geometrical, and hence perceptual, organization. Subjects (n=16) were presented with two test intervals, one containing the standard and the other the comparison stimulus, and had to decide which one persisted longer. Aligned and misaligned Varin stimuli were used as standards as well as comparisons. The standard was presented for a fixed duration of 150ms and was paired randomly with comparisons of 100, 133, 150, 166, 200ms durations. We found that a misaligned comparison had to be presented about 25ms longer than an aligned comparison in order to appear to be of equal duration as the aligned standard. An aligned comparison on the other hand could be about 13ms shorter than a misaligned comparison in order to be perceived as equally long as a misaligned standard. Hence systematic investigation confirmed the casual observation of longer persistence of a geometrically (perceptually) meaningful shape compared to identical but disorganized information. We conjecture that the greater persistence reflects the activation of a recurrent network in lateral occipital or more anterior cortex, driven by and feeding back to V1/V2.
We thank F. Geringswald for help with data collection. The work was supported by a TransCoop grant from the Humboldt foundation to MM and RS.