Evidence for two types of spatial representations: Hemispheric specialization for categorical and coordinate relations.

Analyses of human object recognition abilities led to the hypothesis that 2 kinds of spatial relation representations are used in human vision. Evidence for the distinction between abstract categorical spatial relation representations and specific coordinate spatial relation representations was provided in 4 experiments. These results indicate that Ss make categorical judgments—on/off, left/right, and above/below—faster when stimuli are initially presented to the left cerebral hemisphere, whereas they make evaluations of distance—in relation to 2 mm, 3 mm, or 1 in. (2.54 cm)—faster when stimuli are initially presented to the right cerebral hemisphere. In addition, there was evidence that categorical representations developed with practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Form-specific visual priming in the right cerebral hemisphere.

Results of 4 experiments indicate that both within-modality and case-specific visual priming for words are greater when test stimuli are presented initially to the right cerebral hemisphere (RH). In contrast, neither within-modality nor case-specific explicit memory for words is greater when stimuli are presented initially to the RH. Priming is measured using word-stem completion, and explicit memory is measured using word-stem cued recall. In both cases, Ss first rate how much they like words, and then word stems are presented briefly to the RH (in the left visual field) or to the left hemisphere (in the right visual field). Results suggest that at least 2 separate systems encode the visual representations that produce priming. The system that is more effective in the RH is better at representing form-specific information, whereas another system that is not more effective in the RH does not distinguish among distinct instances of word forms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A computational analysis of mental image generation: Evidence from functional dissociations in split-brain patients.

Recent efforts to build computer simulation models of mental imagery have suggested that imagery is not a unitary phenomenon. Rather, such efforts have led to a modular analysis of the image-generation process, with separate modules that can activate visual memories, inspect parts of imaged patterns, and arrange separate parts into a composite image. This idea was supported by the finding of functional dissociations between the kinds of imagery tasks that could be performed in the left and right cerebral hemispheres of 2 patients (a 19-yr-old male and a 32-yr-old female) who had previously undergone surgical transection of their corpus callosa. The left hemisphere in both Ss could inspect imaged patterns and could generate single and multipart images. In contrast, although the right hemisphere could inspect imaged patterns and could generate images of overall shape, it had difficulty in generating multipart images. Results suggest a deficit in the module that arranges parts into a composite. The observed pattern of deficits and abilities implied that this module is not used in language, visual perception, or drawing. Findings also suggest that the basis for this deficit is not a difficulty in simply remembering visual details or engaging in sequential processing. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the pictorial properties of visual images: Effects of image size on memory for words.

In 4 experiments 82 university students formed mental images of pairs of named objects touching and interacting in some way. On half of the trials, one member of the pair was imaged such that it was at a small subjective size; on the remaining half of the trials, both objects were imaged at normal relative sizes. Ss rated their images in terms of vividness. Results of an unexpected memory test presented after all the items had been rated reveal poorer recall of words encoded as smaller images. This result was not due to differences in imaginal relations between the imaged objects in the 2 conditions, nor was it due to greater ease in constructing images including a reduced member. In addition, pairs including a subjectively tiny image were rated as less vivid than pairs including images only of normally sized objects. A regression analysis indicated that the memory deficit was due to size per se and was not a consequence of differences in vividness induced by the size manipulation. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Can patients with obsessive-compulsive disorder discriminate between percepts and mental images? A signal detection analysis.

Signal detection analysis was used to test three hypotheses for repetitive thoughts and behaviors characteristic of obsessive-compulsive disorder (OCD). Patients might have (a) low sensitivity for the difference between having seen something or having imagined seeing it, (b) a high criterion for this discrimination, or (c) difficulty associating context with information in memory. Subjects judged viewed words or imagined words and later indicated which were actually seen. Patients with OCD discriminated seen from imaged words significantly better than normal control subjects, as evidenced by higher d′ scores on a recognition memory task. Groups did not differ in response criterion, β, used to decide whether words had been seen or imaged. Implications for the study of OCD from an information-processing perspective are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On computational evidence for different types of spatial relations encoding: Reply to Cook et al. (1995).

Computational models in psychology play an increasingly important role in characterizing theoretical distinctions, understanding empirical results, and formulating new predictions. However, the proper use of models is subject to debate and interpretation, as Cook, Früh, and Landis (see record 1995-31404-001) have demonstrated in a critique of neural network simulations reported by Kosslyn, Chabris, Marsolek, and Koenig (see record 1992-37420-001). These simulation results supported a distinction between two types of spatial relations encoding. Cook et al argue that Kosslyn et al's models did not process "spatial" representations and that input–output correlations rather than properties of spatial relations encoding processes explain the performance of the models. This article provides conceptual and analytic rebuttals of those criticisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic retrieval in children and adults.

Studied the processes by which 15 undergraduates and 48 8-, 11-, and 13-yr-olds retrieved semantic information from long-term memory. Ss were timed as they judged whether sentences pairing animal names and properties (e.g., "A lion has a mane") were true. Relationships between animal names and properties were varied in 2 ways: properties were at (a) 1 of 3 levels of "saliency" (rated association strength) and (b) 1 of 3 levels of specificity. Closely comparable results were obtained at each age level. Sentences with highly salient properties were verified more quickly than were those with less salient properties, and statements with low-specificity properties were verified more quickly than sentences with more specific properties. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual-spatial abilities of pilots.

US Air Force pilots and control Ss participated in 5 experiments, each of which assessed a different type of visual-spatial ability. Although pilots judged metric spatial relations better than did nonpilots, they did not judge categorical spatial relations better than did nonpilots. Pilots mentally rotated objects better than did nonpilots, but pilots did not extrapolate motion, scan images, or extract visual features from objects obscured by visual noise better than did nonpilots. The results imply that efficient use of specific processing subsystems is especially important for, and characteristic of, pilots. The possible neuropsychological bases for the enhanced abilities and their susceptibility to change are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Varieties of size-specific visual selection.

Compared time to evaluate stimuli of varying sizes. When Ss expect an upcoming stimulus to be a certain size, response time increases with the disparity between expected and actual size. There are, however, 2 size adjustment processes, and they reflect 2 types of visual selection. In the first, a shape-specific image representation is used to separate a visual object from a superimposed distractor. These representations require the type of slow size scaling demonstrated in imagery experiments. The second size scaling process is faster and not shape-specific. At any given time the visual system is set to process information at a particular scale, and that scale can be adjusted to match an object's size. Because both selection mechanisms depend on size, they probably occur at a relatively low, spatially organized processing level. These findings lead to a new explanation for results that had been taken as evidence for attentional selection at the level of object representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)