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Peter Thompson; Adapting to missing fundamental square waves: a replication of an unreported experiment. Journal of Vision 2002;2(7):740. doi: https://doi.org/10.1167/2.7.740.
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Adelson (1982) reported that a square wave grating, missing its fundamental and stepped to the right in 90 deg phase jumps, appears to move to the left. This result, unpredicted by correspondence and cross-correlational theories of motion perception, is easily explained by looking at the spatio-temporal characteristics of the stimulus, since the largest component of the stimulus, the 3rd harmonic actually does move to the left, the jump being 270 deg of its cycle to the right which is equivalent to a 90 deg jump of its cycle to the left. An obvious question (and one that almost certainly has been asked several times) is what happens if we adapt to this 90 deg jumping missing fundamental stimulus; in which direction will a subsequently viewed stationary 3rd harmonic appear to move? We have carried out a series of experiments adapting to 90 deg jumping square waves, with and without their fundamental component, and testing on a variety of stationary stimuli. In one critical condition we have found that following adaptation to the 90 deg rightward-jumping square-wave grating a stationary 3f-only test stimulus appeared to move to the left, i.e. in the same direction as the 3f component of the adaptation pattern. Although this result might be interpreted as support for the global motion determining the direction of the MAE we shall present evidence to support the view that the broad spatial tuning of the movement aftereffect is responsible for this result.
Adelson (1982) Some new motion illusions — and some old ones, analysed in terms of their Fourier components. Investigative Ophthalmology and Visual Science 22 (3) 144
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