Context: Psychometric Functions for the Effects of Context on Contrast...

Description Usage Format Details Source References Examples

Description

Yes-No psychometric functions in which observers reported whether a vertical bar (the target) was present on each trial in the presence of contextual bars.

Usage

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Format

A data frame with 120 observations on the following 5 variables.

Obs

a factor with levels A B C D E F identifying each observer.

ContCntr

a numeric vector indicating the contrast of the contextual elements.

TargCntr

a numeric vector indicating the contrast of the target.

NumYes

an integer vector indicating the number trials on which the observer responded as having seen the target.

NumNo

an integer vector indicating the number of trials on which the observer responded as not haveing seen the target.

Details

The number of trials on which the target was detected is reported as a function of its contrast. The target bar was presented in the context of 6 aligned vertical bars (3 above and 3 below) and the 4 conditions correspond to 4 levels of contrast of the contextual bars, including a 0 contrast condition, i.e., no contextual bars.

Source

Data kindly provided by Li Zhaoping

References

Zhaoping L. \& Jingling L. (2008) Filling-in and suppression of visual perception from context—a Bayesian account of perceptual biases by contextual influences, PLoS Computational Biology 4(2): e14 doi:10.1371/journal.pcbi.0040014

Examples

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data(Context)
Context <- within(Context, Pc <- NumYes/(NumYes + NumNo))
lattice::xyplot(Pc ~ TargCntr | ContCntr, data = Context, 
	groups = Obs,	type = c("l", "p"),
	auto.key = list(space = "right"))


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