Title |
Free-Energy and Illusions: The Cornsweet Effect
|
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Published in |
Frontiers in Psychology, January 2012
|
DOI | 10.3389/fpsyg.2012.00043 |
Pubmed ID | |
Authors |
Harriet Brown, Karl J. Friston |
Abstract |
In this paper, we review the nature of illusions using the free-energy formulation of Bayesian perception. We reiterate the notion that illusory percepts are, in fact, Bayes-optimal and represent the most likely explanation for ambiguous sensory input. This point is illustrated using perhaps the simplest of visual illusions; namely, the Cornsweet effect. By using plausible prior beliefs about the spatial gradients of illuminance and reflectance in visual scenes, we show that the Cornsweet effect emerges as a natural consequence of Bayes-optimal perception. Furthermore, we were able to simulate the appearance of secondary illusory percepts (Mach bands) as a function of stimulus contrast. The contrast-dependent emergence of the Cornsweet effect and subsequent appearance of Mach bands were simulated using a simple but plausible generative model. Because our generative model was inverted using a neurobiologically plausible scheme, we could use the inversion as a simulation of neuronal processing and implicit inference. Finally, we were able to verify the qualitative and quantitative predictions of this Bayes-optimal simulation psychophysically, using stimuli presented briefly to normal subjects at different contrast levels, in the context of a fixed alternative forced choice paradigm. |
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Geographical breakdown
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Germany | 2 | 1% |
Switzerland | 1 | <1% |
Italy | 1 | <1% |
Australia | 1 | <1% |
United Kingdom | 1 | <1% |
United States | 1 | <1% |
Unknown | 185 | 96% |
Demographic breakdown
Readers by professional status | Count | As % |
---|---|---|
Student > Ph. D. Student | 55 | 29% |
Researcher | 36 | 19% |
Student > Master | 21 | 11% |
Professor > Associate Professor | 11 | 6% |
Professor | 11 | 6% |
Other | 40 | 21% |
Unknown | 18 | 9% |
Readers by discipline | Count | As % |
---|---|---|
Psychology | 53 | 28% |
Neuroscience | 25 | 13% |
Agricultural and Biological Sciences | 24 | 13% |
Computer Science | 12 | 6% |
Medicine and Dentistry | 10 | 5% |
Other | 36 | 19% |
Unknown | 32 | 17% |