Gerald M. Murch

Classical conditioning of the McCollough effect: Temporal parameters

Abstract The present paper develops a classical conditioning model of orientation specific colored aftereffects (McCollough Effects) and presents data on the temporal parameters of the CS-UCS relationship in both a delayed and trace conditioning paradigm. In this model, the lined grid in inspection is seen as the conditioned stimulus (CS) and the paired color as the unconditioned stimulus (UCS). The value of this model for further research on the McCollough Effect is discussed.

Color contingent motion aftereffects: single or multiple levels of processing?

Abstract The monocular spiral aftereffect can be observed in the stimulated and unstimulated eye. When the aftereffect is made contingent upon a specific color, transfer does not occur. The experiments reported show this to be the result of separate coding for color and movement, whereby the color coding occurs prior to binocular interaction.

Temporal Gradients of Responses to Subliminal Stimuli

This paper presents three experiments aimed at determining the duration of the effects of subliminal stimulation in a dis-crimination situation. Parts of two letters were shown supraliminally in a three-field tachistoscope. Subliminal completions of these letters were presented which were to be discriminated from two other equally likely alternatives not previously presented subliminally. The presentation of the response categories was delayed for 0, 100, 250, 500, 1000, or 2000 msec. The major results of each experiment indicated increased response probabilities after delays of 0, 100 and 250 msec. A tendency for more rapid responding to correspond to the selection of the subliminal stimulus was observed, however. Lengthening the time in which a response could be made did not increase response accuracy. A general model based on threshold changes of stimulated receptors is presented.

Responses to incidental stimuli as a function of feedback contingency

The effects of incidental stimuli, defined as visual stimuli not under verbal control, upon a selection task were observed as a function of feedback contingency. Ss judged letter pairs to be valid or invalid completions of preceding letter parts. During the presentation of the letter parts, the response pair or an alternative pair of letters was intermittently presented at a threshold value individually determined for each S. One group of Ss received a light feedback of performance contingent upon responding to the incidental stimuli; whereas a second group received a random noncontingent feedback. The results indicated: (a) both groups responded to the incidental stimuli; (b) feedback contingency had no effect on frequency of responding to the incidental stimuli; (c) frequency of responding to the incidental stimuli remained constant over 32 trials.

The role of test pattern background hue in the McCollough effect

Abstract An experiment is reported in which the role of the spectral characteristics of the test pattern used in eliciting the McCollough Effect was explored. It was found that the effect is still observable when the test pattern, which is usually achromatic, is itself chromatic. Two chromatic test patterns were used and the McCollough Effect was measured by comparing colorimetric matches of the test patterns before and after inspection of red/horizontal and blue/vertical grids observed under the usual McCollough paradigm. One chromatic test pattern overlapped spectrally the energy distributions of the two inspection patterns while the second overlapped neither inspection color. The observation of the McCollough effect on such patterns was taken as further evidence in support of the conditioning model of the effect.

CIE x,y coordinates from an inexpensive projection colorimeter

The present paper reports an extension of the design for a projection colorimeter originally proposed by Riggs, 1964. A technique and the necessary calculatory formulas are presented through which the definitions of colors produced by the instrument may be defined in terms of CIE x,y coordinates of chromaticity space. Data on the accuracy of measurements obtained from a random sample of naive Os are also reported.

Variation in hue of a contour-contingent aftereffect due to color adaptation during inspection of the stimulus patterns

The McCollough Effect (a colored line-orientation-contingent aftereffect) has been attributed to the presence of edge detectors specific to wavelength in the human visual system. The present study tests this hypothesis by introducing unlined colored fields into the inspection condition and by comparing the subsequent aftereffect with the aftereffect induced by the inspection condition not including the unlined colored fields. The data indicate that the hues of the aftereffects differ, suggesting that the color and line stimuli may be processed by different populations of neural elements, and that the color-coded edge detector model is not adequate to account for the observations.

An extension of the Riggs projection colorimeter

A method for the construction and calculation of CIE chromaticity coordinates from a simple and inexpensive projection colorimeter is presented. The device allows variation along the dimensions of hue, saturation, and brightness and specification of these variations in terms of chromaticity coordinates, dominant wavelength, relative luminance, and excitation purity.

Colorimetric matches of McCollough aftereffects.

Abstract The colorimetric matches to McCollough Effects generated by various inspection hues sampled across the visible spectrum are reported. The chromaticity coordinates of these matches can not be satisfactorily described as the complement of the inspection hue nor as the result of chromatic adaptation as predicted by Jameson and Hurvichs opponent process model of color vision.