Peak shift revisited: A test of alternative interpretations.

Thomas, David R.; Mood, Kelly; Morrison, Spencer K.; Wiertelak, Eric P.

doi:10.1037/0097-7403.17.2.130

Cited by 47 publications

(89 citation statements)

References 32 publications

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“…Gradient means have been used extensively to measure peak shift in past studies (e.g., Thomas et al, 1991). Adding gradient peak allowed a comparison of shift between groups based on actual peak, rather than on peak estimated from gradient means.…”

Section: Methodsmentioning

confidence: 99%

Temporal dynamics of generalization and representational distortion

2010

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Section: Methodsmentioning

confidence: 99%

Temporal dynamics of generalization and representational distortion

2010

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“…An alternative approach has been to assume that organisms learn about relationships between the stimulus values. Recently, Thomas and colleagues (e.g., Thomas, 1974;Thomas, Mood, Morrison, & Wiertelak, 1991) proposed a relational interpretation of the peak-shift effect, on the basis of principles derived from Helson's (1964) adaptation-level theory. They suggested that the average value of stimuli presented during intradimensional discrimination training forms an adaptation level, or frame of reference, and that organisms learn to respond to a value that is X units above or below this adaptation level.…”

mentioning

confidence: 99%

Spatial peak shift and generalization in pigeons.

Chen

Johnston

1997

Journal of Experimental Psychology: Animal Behavior Processes

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How pigeons generalize across spatial locations was examined in the 4 experiments reported in this article. During training, a square was presented at a fixed height at 1 of 2 horizontal locations on a monitor screen. One location (S +) signaled reward, whereas the other one (S -) signaled no reward. The birds were then tested occasionally with a range of locations. After training with S+ only, the generalization gradient peaked at S + and was approximately Gaussian in shape. After training with equal numbers of S + and S-trials, response rates were higher on the S + side of the distribution. This asymmetry diminished over testing. When the S + and S-were close together, the peak of responding was shifted on initial generalization tests. Generalization gradients along the orthogonal vertical dimension were approximately exponential in shape. This is the first demonstration of generalization and peak shift in the spatial domain.An important task for the experimental analysis of behavior has been to understand how stimuli present when behavior is reinforced to gain control over the behavior. Stimulus generalization--cesponding in a similar fashion despite changes in properties of a stimulus--and discriminationmresponding differently when a stimulus property is changed--are opposite ends of a continuum of stimulus control. Stimulus control typically is indexed by decremental stimulus generalization gradients, in which increasing changes in a stimulus value lead to increasing changes in responding.Guttman and Kalish (1956) conducted a now-classic study of stimulus generalization in pigeons. They reinforced pigeons on an intermittent schedule for pecking a key in the presence of a monochromatic light source. Different groups of pigeons were trained with different spectral stimuli. After a steady rate of responding emerged, the pigeons were tested in extinction with a range of spectral wavelengths on either side of, and including, the training value. Plots of responses as a function of spectral wavelength showed orderly generalization gradients, with the highest rate of responding at the Ken Cheng, School of Behavioural Sciences, Macquarie University, Sydney, Australia; Marcia L. Spetch and Michael Johnston, Department of Psychology, University of Alberta, Edmonton, Alberta, Canada.This research was supported by grants from Macquade University and the Australian Research Council and a Natural Sciences and Engineering Council of Canada research grant. Some of these data were collected as part of the thesis requirement for an honors bachelor of science degree in psychology by Michael Johnston.We thank D. Kelly and S. Reid for assistance in conducting the research.Correspondence concerning this article should be addressed either to Ken Cbeng, School of Behavioural Sciences, Macquade University, Sydney NSW 2109 Australia, or to Marcia L. Spetch, Department of Psychology, University of Alberta, Edmonton, Alberta, Canada T6G 2E9. Electronic mail may be sent via Intemet either to kcbeng@bnnyip.bhs.mq.edu.au or to mspetch@psy...

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“…Although categorical structure is certainly implied by these effects, we cannot say that categorical differences between facial expressions are the only ones captured by caricature. As Rhodes and Tremawan (1994) point out, enhancement of category signal can and does occur when the features to be distinguished are simple differences on a continuum (the peak-shift phenomenon; see Thomas, Mood, Morrison, & Wiertelak, 1991). A dimensional theory of expression (see, e.g., ) may fit these findings as well as a purely categorical one.…”

Section: Discussionmentioning

confidence: 88%

Enhancing images of facial expressions

Benson

Campbell

Harris

et al. 1999

Perception & Psychophysics

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Facial images can be enhanced by application of an algorithm-the caricature algorithm-that systematically manipulates their distinctiveness (Benson & Perrett, 1991c;Brennan, 1985).In this study, we first produced a composite facial image from natural images of the six facial expressions offear, sadness, surprise, happiness, disgust, and anger shown on a number of different individual faces (Ekman & Friesen, 1975). We then caricatured the composite images with respect to a neutral (resting) expression. Experiment 1 showed that rated strength of the target expression was directly related to the degree of enhancement for all the expressions. Experiment 2, which used a free rating procedure, found that, although caricature enhanced the strength of the target expression (more extreme ratings), it did not necessarily enhance its purity, inasmuch as the attributes of nontarget expressions were also enhanced. Naming of prototypes, of original exemplar images, and of caricatures was explored in Experiment 3 and followed the pattern suggested by the free rating conditions of Experiment 2, with no overall naming advantage to caricatures under these conditions. Overall, the experiments suggested that computational methods of compositing and caricature can be usefully applied to facial images of expression. Their utility in enhancing the distinctiveness of the expression depends on the purity of expression in the source image.

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Peak shift revisited: A test of alternative interpretations.

Cited by 47 publications

References 32 publications

Temporal dynamics of generalization and representational distortion

Temporal dynamics of generalization and representational distortion

Spatial peak shift and generalization in pigeons.

Enhancing images of facial expressions

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