Spatial frequency content of visual imagery

Three experiments employing the McCollough paradigm were conducted to determine the spatial-frequency content of visual imagery. In Experiment 1, large and reliable pattern-contingent color aftereffects were obtained after adaptation to visual imagery. The direction of the aftereffects indicated that subjects were adapting to higher spatial frequencies in their imagery. These results contrast with the data of Experiment 2, which demonstrate that color aftereffects obtained with adaptation to physically present stimuli are mediated by the fundamental spatial frequency components. The magnitude of the imagery-induced aftereffects in Experiment 1 equaled the magnitude of the externally induced aftereffects obtained in Experiment 2 with the same subjects. By blurring the to-be-imaged patterns (Experiment 3), the fundamental Fourier components became the salient perceptual features of the stimuli, and the direction of the imagery-induced aftereffects was reversed from that of Experiment 1, indicating that the spatial frequency content of the imagery had changed from higher to lower frequencies. Under normal viewing conditions, subjects use the higher spatial frequencies associated with the perceptually salient edges of stimuli to construct their images. The results of Experiments 1 and 3 are discussed in light of a current controversy over the nature of information representation in imagery, and it is concluded that support has been obtained for the analog model of visual imagery.     

Path integration while ignoring irrelevant movement

Participants attempted to return to the origin of travel after following an outbound path by locomotion on foot (Experiments 1-3) or in a virtual visual environment (Experiment 4). Critical conditions interrupted the outbound path with verbal distraction or irrelevant, to-be-ignored movements. Irrelevant movement, real or virtual, had greater effects than verbal or cognitive distraction, indicating inability to ignore displacement during path integration. Effects of the irrelevant movement's direction (backward vs. rightward) and location (1st vs. 2nd leg of path) indicated that participants encoded a configural representation of the pathway and then cognitively compensated for the movement, producing errors directly related to the demands of compensation. An encoding-error model fit to the data indicated that backward movement produced downward rescaling, whereas movement that led to implied rotation (rightward on 2nd leg) produced distortions of shape and scale.     

Relationship between language skills and academic achievement in first grade

The ability of scores on the Early Prevention of School Failure battery to predict Stanford Achievement Test scores was examined. Participants included 280 first-grade students who were administered the battery at the beginning of kindergarten and the Stanford Achievement Test at the end of first grade. Principal factor analysis based on the oblique rotation exhibited simple structure between scores on the Peabody Picture Vocabulary Test-Revised, the Preschool Language Scale, and the Stanford Achievement Test (verbal or language factor), with the Draw-A-Man test and the Developmental Test of Visual-Motor Integration-Revised loading on a separate factor (motor factor). Results suggest that language-based skills were highly associated with later academic performance in school-aged children.     

When the central executive lets us down: schemas, attention, and load in a generative working memory task

Participants were asked to generate a single sequence of numbers in between two bounds. By varying the requested sequence length and way in which the question is posed, this paradigm enables assessment of the contributions to central executive functioning of schema, focus of attention, and load. With sequences of three or four numbers, a quarter of the sample failed fully to comply with the instructions. They generated an incorrect number of numbers or went outside the specified bounds. With sequences of six numbers, more than half of the sample infringed one or more of the constraints. Participants consistently generated sequences with particular generic properties. The overall frequency and patterns of infringements suggest that a substantial proportion of participants focused their conceptual attention on sequence content and often neglected the problem of how thelength and boundary constraints were going to be evaluated either before or during response delivery.     

COMPETITION BETWEEN POSITIVE AND NEGATIVE REINFORCEMENT IN THE TREATMENT OF ESCAPE BEHAVIOR

We compared the effects of reinforcing compliance with either positive reinforcement (edible items) or negative reinforcement (a break) on 5 participants' escape-maintained problem behavior. Both procedures were assessed with or without extinction. Results showed that compliance was higher and problem behavior was lower for all participants when compliance produced an edible item rather than a break. Treatment gains were achieved without the use of extinction. Results are discussed regarding the use of positive reinforcement to treat escape behavior.     

Effects of spatial filtering and lack of effects of visual imagery on pattern-contingent color aftereffects

Checkerboards contain fundamental two-dimensional Fourier components oriented 45° from the edges of individual checks. Previous studies have shown that contingent color aftereffects following adaptation to chromatic checkerboard stimuli were associated with the fundamental components rather than the edges, In the present experiments, we measured contingent color aftereffects, using the method of constant stimuli, after subjects adapted to unfiltered checkerboards and checkerboards with the fundamental Fourier components removed. The adaptation stimuli were magenta (or green) squares and green (or magenta) diamonds; the test stimuli were vertical or oblique sine-wave gratings with different saturations, After adaptation to unfiltered checkerboards, aftereffects contingent on the fundamental components were obtained. In contrast, after adaptation to filtered stimuli, aftereffects of smaller magnitude were found to be aligned with the edges. The data support the previous findings of spatial-frequency-contingent color after-effects with checkerboard adaptation stimuli and indicate that the aftereffects can be associated with edges if the fundamental components of adaptation stimuli are removed by spatial filtering. We reexamined the possibility of color aftereffects induced by imagery of checkerboards. Contrary to the previous reports, no significant aftereffects were obtained.