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Gregory Francis; Developing a new quantitative account of backward masking. Journal of Vision 2002;2(7):212. doi: 10.1167/2.7.212.
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© ARVO (1962-2015); The Authors (2016-present)
Backward masking refers to impaired performance on some judgment of a brief target stimulus when it is followed by a mask stimulus. The effect of the mask often varies with the interstimulus interval (ISI) between the target and the mask, so that a plot of the target percept strength against ISI produces a u-shape. A new general explanation for u-shaped backward masking is analyzed and found to predict shifts in the ISI value that produces strongest masking (the bottom of the u-shape). As mask intensity or duration increases, masking generally becomes stronger and the ISI for maximal masking shifts to smaller values. As target intensity or duration increases, masking generally becomes weaker and the ISI for maximal masking shifts to larger values. Within the model, a calculation of the target's percept strength must be mapped to behavioral responses. Changes in this mapping can modify the overall strength of masking, but do not modify the ISI value that leads to maximal masking. Six sets of masking data that show variation in overall strength of masking are then interpreted by the general explanation according to how the ISI value for maximal masking changes. The data sets explore effects of: practice, eccentricity, light adaptation, flicker adaptation, attention, and a word superiority effect. The resulting interpretations promote the development of a new theory of backward masking that uses the properties of the general explanation. The new theory suggests interpretations of the data that are sometimes novel, often more precise, and sometimes contrary to interpretations that are prevalent in the literature.
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