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Remy Allard, Patrick Cavanagh; Orientation uncertainty reveals different detection strategies in noise. Journal of Vision 2010;10(7):1371. doi: 10.1167/10.7.1371.
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© ARVO (1962-2015); The Authors (2016-present)
Widely used external noise paradigms are based on the assumption that adding external noise quantitatively affects performance but does not qualitatively affect the processing strategy. However, we recently found evidence in a crowding task that some forms of external noise do change processing strategies at higher levels and we confirm this effect of noise on strategy here using an uncertainty reduction procedure. Specifically, we measured the impact of orientation uncertainty (fixed- versus randomized-orientation) on contrast detection thresholds of a sine wave grating in three different noise conditions: noiseless, spatiotemporally localized noise (i.e. signal and noise shared the same spatiotemporally window) and spatiotemporally extended noise (i.e. continuously displayed full screen dynamic noise). In the no-noise and extended-noise conditions, knowing the orientation of the signal to detect had little impact on performance (orientation uncertainty increased contrast thresholds by 4% and 8%, respectively) suggesting that detection was not based on an orientation recognition strategy but rather mediated by an energy-based strategy as it is generally assumed. In contrast, knowing the orientation of the signal substantially improved performance in the localized-noise condition (orientation uncertainty increased contrast thresholds by 28%) suggesting that detection was based on an orientation recognition strategy. We conclude that spatiotemporal localized external noise can qualitatively affect the processing strategy. Our results suggest that external noise paradigms should use only spatiotemporally extended dynamic noise in order to match the likely characteristics of the internal noise and avoid triggering qualitative changes in the processing strategy. These results raise questions about the validity of the conclusions of many previous studies using external noise paradigms with localized external noise.
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