Response scales and sequential effects in judgment

There are persistent sequential effects in judgment tasks. For example, responses tend to be similar to the value of the just-prior stimulus. This is called assimilation. Also, if feedback is or is not provided after each trial, then responses contrast with or assimilate to, respectively, each of several earlier stimuli in the sequence. These context effects have been shown to be independent of stimulus modality and of the range of stimulus values within a modality. By providing different sets of feedback in order to affect the responses used, this article shows that these sequential effects in judgment data are also independent of the form and range of the scale of responses used to label stimuli.     

Multidimensional scaling of subjective colors by color-blind observers

Temporal coding theories of color vision suggest explanations of flicker-induced subjective colors such as those that appear on Benham’s disk. If color blindness were due simply to photopigment anomalies, then subjective colors might be elicited by central patterns of neural activity in color-blind observers that mimic those which the cones normally produce in colornormal observers. We had color-normal and color-blind observers scale subjective colors like those on Benham’s disk for similarity. The inferred color spaces for six normal observers resembled the familiar hue circle, but the spaces for five red-green-deficient observers were compressed along the red-green axis. This is consistent with the position that flicker colors are due to retinal processes, and suggests that color blindness may involve variations of the central nervous system in addition to photopigment anomalies.     

Difference information in brightness perception

Contour information generated by moving retinal images has been shown by others to be the principal determinant of perceived color. The data presented here show that, for brightness, this information reflects only differences between adjacent stimulus areas. The entire distribution of difference information from contours in the visual field must be specified in order to predict the brightness at any point.     

Holistic vs. attribute repetition effects in classifying stimuli

The effect of the just previous stimulus on the current response was determined in three speeded classification experiments. When the stimuli were perceptual patterns, and when they were words, there was marked facilitation if the previous stimulus was identical to the current stimulus. When successive perceptual stimuli were composed of identical elements, but in a changed configuration, there was no measureable sequential effect on “same” response times. These results are for integral stimuli. When stimuli are not integral, as with some studies in the literature, it is suggested that each two-dimensional nonintegral stimulus is treated by the observer as two objects. In those cases, responses can be facilitated by repetition of that object on which responses were based on the previous trial, and this can occur when a value of the other dimensions (other objects) has not repeated. Accordingly, the processing of integral and nonintegral stimuli must be considered separately when attempting to evaluate process models. Further, facilitation due to stimulus repetitions does not account for all of the differences in response times between various classification tasks. These additional differences may be attributed to a multidimensional range effect analogous to the range effects found in psychophysical tasks.     

Holistic versus analytic process models: a reply

Two classes of stimulus process models are considered in this reply to Dykes and Cooper. It is shown that analytic models which assume that stimuli are initially processed in terms of constituent dimensions do not account for large amounts of published data. It is also shown that the holistic-discriminability model that Dykes and Cooper reject is nonetheless consistent with their results and predicts all of the data for which their analytic model was constructed to account.     

Context and goodness in a focusing task

Attention, Perception, & Psychophysics - In a focusing task, people respond positively to one stimulus and negatively to all other stimuli that occur. The task has been called focusing in...