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Katharina Anton-Erxleben, Katrin Herrmann, Marisa Carrasco; Independent effects of adaptation and attention on speed perception. Journal of Vision 2011;11(11):230. doi: 10.1167/11.11.230.
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Introduction: Both attention and adaptation influence perception of visual stimuli. Adaptation typically causes a repulsive shift in perception of a given feature away from the adaptor, i.e., either an over- or underestimation, by shifting neuronal population activity away from the adaptor value. Spatial attention leads to an overestimation of several visual features, including motion speed (e.g., Turatto et al., 2007). This effect may similarly be caused by a shift in neuronal population activity. If a common neuronal population mediates both effects, adaptation and attention should interact. The magnitude and direction of the interaction should depend on the specific value of the adaptor: Attention and fast adaptor speeds have opposing effects on perceived speed and should thus counteract. Slow adaptor speeds often only have a weak effect and thus should not modulate the effect of attention. Methods: Here, we combine spatial attention and adaptation in a psychophysical paradigm. An uninformative, exogenous cue directed covert spatial attention to one of two moving stimuli. Observers reported which one they perceived as moving faster. Either the attended or the unattended stimulus was preceded by an adaptor moving at one of two speeds, slow or fast. Both speeds were chosen so that the fast adaptor yielded a strong adaptation effect, whereas the slow adaptor served as a control condition. We measured the point of subjective equality (PSE) for perceived speed. Results & Conclusions: Peripheral cueing shifted the PSE compared to neutral cueing consistent with an increase in perceived speed. This effect of attention, however, did not depend on the adaptation speed. In additional experiments, both the effect of attention and the effect of adaptation on perceived speed were found to be of similar magnitude when tested in isolation and when tested in combination. These results suggest that attention and adaptation affect perceived speed independently.
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