![]() This illusion is similar to that described by Van der Burg, Olivers, Bronkhorst, and Theeuwes ( 2008), where temporally related (but spatially uncorrelated) auditory information is provided to subjects performing a visual search task. This process, maybe mediated by some attentional mechanisms, was so effective that on some trials subjects reported the dancing dots to be segregated from the noise, a sort of “pop-out” phenomenon. As the tap auditory sequences used in this experiment were the original sequences (not substituted with a template), they contained many distinct features with high salience (for example, shuffles, pullbacks, and toe punches) that could provide further information. Although they were uninformative in their own right, the synchronized auditory signals could have served as temporal references, thereby narrowing the uncertainty window about the timing of the visual signals (and helping to ignore the noise signals). Possibly, the simplest mechanism to account for this facilitation could be reduction of temporal uncertainty. There was no facilitation when the visual and auditory sequences were out of synchrony. The first experiment showed that a non-informative audio sequence can facilitate the recognition of visual tap dance sequences, provided that the taps are in synchrony with the visual motion. The primary aim of these experiments was to investigate if auditory and visual signals integrate in the perception of a form of audiovisual “biological motion”: tap dancing. We show that with these natural-like stimuli, integration does occur, at a level greater than predicted by mere statistical advantage. In this study we pursue further audiovisual integration for a form of biological motion where both sight and sound provide useful information: tap dancing. ![]() ( 2007) demonstrated audiovisual integration for point-source biological motion (Johansson, 1973), showing that reaction times for detecting visual biological motion embedded in noise was enhanced by the presence of congruent auditory “motion” (advancing or retreating steps). On the other hand Meyer, Wuerger, Röhrbein, and Zetzsche ( 2005) reported that audiovisual integration was stronger and direction specific when visual stimuli comprised spatially curtailed objects in motion (rather than whole-field motion) and auditory stimuli a physical signal source providing high-quality localization. ![]() This small audiovisual advantage was consistent with a statistical combination of information, rather than of a functional neural integration of visual and auditory motion. Both Alais and Burr ( 2004a) and Wuerger, Hofbauer, and Meyer ( 2003) reported facilitation for audiovisual motion perception, but the effects were small and, importantly, unspecific for direction: rightward auditory motion facilitated leftward visual motion as much as did leftward auditory motion. Surprisingly, the psychophysical results are less clear. These neurophysiological results reinforced behavioral studies in cat (Stein, Huneycutt, & Meredith, 1988) and also humans (Alais & Burr, 2004b Ernst & Banks, 2002 Frassinetti, Bolognini, & Làdavas, 2002), indicating that mammalian perceptual systems are indeed capable of exploiting multiple sensory stimulation to facilitate the detection of external signals. For example, around one third of them show strongest responses when visual and auditory patterns of an action they are sensitive to are presented together relative to unimodal presentations (Keysers et al., 2003). Auditory and visual signals interact in defining the response profile of these neurons. In addition, audiovisual mirror neurons respond even when only the sound of an action is perceived, without any significant activation for auditory stimuli not related to action (Kohler et al., 2002). Mirror neurons respond both when a monkey observes an action as well as when he makes a similar action (Gallese, Fadiga, Fogassi, & Rizzolatti, 1996 Rizzolatti, Fadiga, Gallese, & Fogassi, 1996). Recent physiological studies on monkey have revealed neurons in the ventral premotor cortex (area F5) that show the characteristics of mirror neurons along with specific sensitivity to audiovisual stimuli.
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