Temporal judgments in multi-sensory space.

To successfully interact with the environment requires a combination of stimulus recognition as well as localization in both space and time, with information moreover coming from multiple senses. Several studies have shown that auditory stimuli last subjectively longer than visual ones of equal duration. Recently, it has also been suggested that stimulus position affects duration perception. The present study investigated how lateral spatial presentation influences sub-second visual and auditory duration judgments. Five experiments were conducted using the duration discrimination paradigm, wherein two stimuli are presented sequentially and participants are asked to judge whether the second stimulus (comparison) is shorter or longer in duration than the first (standard). The number of stimulus positions and the way in which different modality trials were presented (mixed or blocked) varied. Additionally, comparisons were made either within or across modalities. No stable effect of location itself was found. However, in mixed modality experiments there was a clear over-estimation of duration in visual trials when the location of the comparison was different from the standard. This effect was reversed in the same location trials. Auditory judgments were unaffected by location manipulations. Based on these results, we propose the existence of an error-mechanism, according to which a specific duration is added in order to compensate for the loss of duration perception caused by spatial attention shifts between different locations. This mechanism is revealed in spatial and modality-mixed circumstances wherein its over-activation results in a systematic temporal bias.