Nifedipine blocks retention of a visual discrimination task in chicks.

Reports that the dihydropyridine Ca2+ channel antagonists may facilitate memory led to the present study of the behavioral effects of nifedipine. Ninety-two 4-day-old male chicks received 0, 100 nM, 100 microM, or 10 mM nifedipine. Drugs were administered in volumes of 2 microliters into the fourth cerebral ventricle 5 min before training on a visual discrimination task. Nifedipine did not produce any detectable changes in behavior during acquisition trials. Retention, however, was impaired 24 h after training in the 100 nM and 100 microM nifedipine-treated chicks, which made significantly more errors than controls. Nifedipine did not affect the amount of time required to complete the task. No effects on body weight gain were detected, suggesting that the memory impairment was not due to a change in feeding behavior. These data are discussed in terms of the role of calcium-dependent processes in memory.     

Attentional demands of processing shape in three-dimensional space: evidence from visual search and precuing paradigms.

The hypothesis that representation of projective shape is preattentive whereas representation of objective shape in three-dimensional space requires allocation of attention was tested in 2 visual search and 2 precuing experiments. In the visual search experiments, the slope for projective shape search was expected to approach 0 and that for objective shape search was expected to be a positive monotonic function of set size. In the precuing experiments, the effects of precuing were expected to be largely limited to the task requiring representation of objective shape. The overall pattern of results conformed to expectations. The findings are interpreted in the context of a model of shape-at-a-slant processing set out by Epstein and Lovitts (1985) and Epstein and Babler (1989, 1990).     

Wayfinding on foot from information in retinal, not optical, flow.

People find their way through cluttered environments with ease and without injury. How do they do it? Two approaches to wayfinding are considered: Differential motion parallax (DMP) is a retinal motion invariant of near and far objects moving against fixation; the information in optical flow (IOF) is a radial pattern of vectors, relying on decomposition of retinal flow. Evidence is presented that DMP guides wayfinding during natural gait, accounting for errors as well as correct responses. Evidence against IOF is also presented, and a space-time aliasing artifact that can contaminate IOF displays is explored. Finally, DMP and IOF are separated, showing they can yield different results in different environments. Thus, it is concluded that (a) DMP and IOF are different, (b) DMP and not IOF is used for wayfinding, (c) moving observers do not usually decompose retinal flow, and (d) optical flow may be a mathematical fiction with no psychological reality.     

General slowing alone cannot explain age-related search effects: reply to Cerella (1991)

Cerella (1991) has argued that the performance of older adults in the Fisk and Rogers (1991) study is a linear function of the performance of younger adults that is independent of task-specific cognitive requirements. We demonstrate that this is not the case. First, we show that the scatter plot analyses used by Cerella can hide the very task-specific age-related slowing they were designed to reveal. Second, we demonstrate that the percentage of variance explained by such analyses can be misleading. Third, we show that there are reliable differences across tasks in the parameters relating younger and older adults' performance. Finally, we argue that the general, task-independent proportionate slowing that Cerella suggested explains so much of the variance in age-related performance is actually an average slowing that is a function of a relatively small task-independent and a relatively large task-dependent factor.     

Some properties of configural learning: an investigation of the transverse-patterning problem.

Little is known about the conditions that encourage animals to learn to use configural associations to guide their behavior or the consequences of such learning for transfer. This study provided some information about these issues by examining how rats solve the transverse-patterning problem, which requires a configural solution (Spence, 1952). Animals had to concurrently solve 3 simultaneous visual discriminations, represented abstractly as A+ versus B-, B+ versus C-, and C+ versus A-. Experiment 1 indicated that rats use a configural solution even when the problems have an elemental solution, provided that the significance of 1 element (e.g., B) shared by 2 problems is ambiguous (e.g., A+/B-; and B+/C-). Experiments 2 and 3 suggested that, when stimulated to use a configural solution by solving the A+/B- and B+/C- problems, rats transfer the configural solution to problems that have no ambiguous elements.     

Multivariate genetic analysis of specific cognitive abilities in the Colorado adoption project at age 7

A multivariate hierarchical model of specific cognitive abilities was fitted to data from 7-year-old adopted and nonadopted sibling pairs in the Colorado Adoption Project in order to assess differential genetic influence on specific mental abilities. Model fitting results and Schmid-Leiman (Schmid & Leiman, 1957) transformations reveal significant heritable variation for verbal, spatial, and memory factors independent of general cognitive ability for the eight ability tests examined. In contrast, environmental influences are primarily measure-specific. The results suggest genetic effects in middle childhood that differentially influence mental ability scores.     

Reinstatement of latent inhibition following a reminder treatment in a conditioned taste aversion paradigm.

Reminder treatments have been shown to facilitate the retrieval of a variety of conditioned responses. Whether or not similar results would occur with an experimental paradigm which involves primarily memory for a stimulus, i.e., where no particular response is specified, is unclear. Accordingly, using Sprague-Dawley rats, we employed a latent inhibition paradigm with a long (10 days) retention interval between sucrose (CS) preexposure and sucrose-illness pairing (training). The results demonstrated a loss of latent inhibition following the 10-day retention interval suggesting "forgetting" of the CS preexposure. However, placing a single reminder exposure to the CS within the preexposure-to-training interval reinstated the preexposure effect. Controls indicated that in the absence of the initial preexposure the reminder per se did not produce latent inhibition. Thus, a reminder can reinstate a stimulus attribute (flavor representation) and explicit conditioned responses.     

Design and implementation of a program for AIDS prevention in female prostitutes

The Companeros model of HIV infection prevention in Ciudad Juarez, Mexico, is presented as conceived by the National Institute of Drug Abuse (NIDA). 518 women who were IV drug users, sexual partners of drug addicts, or prostitutes were requested to participate, and 232 consented. Initial and follow-up AIDS assessments were utilized along with an assessment of sociodemographic variables, including knowledge, sexual behavior, use and abuse of drugs, and previous health history. Educative sessions about AIDs and sexually transmitted diseases (STDs) included group discussions and interaction, video watching, personal experiences, and sociodramas. 61% of prostitutes were 29, 12.6% were 13-19 years old, 31.1% were aged 30-39, and 8.9% were 40. 11% had no formal education, 58% had 6 years of primary and part of 3 years of secondary education, only 18.6% completed secondary education; and 13% had higher education. 19% lived in a hotel or shelter. Family disintegration reached 44%; these women did not live with their children. Only 5.2% thought they had excellent health, 51% said they had good health, 31% stated they had average health, and 12% admitted having had health problems. 14.6% had genital ulcers, 1.3% had herpes, 15% had gonorrhea, and 10% had syphilis. Since IV drug use among these women was almost nonexistent sexual relations constituted the principal risk factor. Responses to a questionnaire showed that the most frequent sexual behavior was vaginal penetration followed by fellatio; anal penetration was less common. 34.9% of the women practiced fellatio without protection, 16.3% had anal intercourse without protection. The proportion of AIDS cases in Mexico in women of reproductive age was growing at an exponential rate, possible because of misinformation about AIDS, a history of STDs, and a low rate of condom use.     

Variations in characteristic perceptual asymmetry: modality specific and modality general components.

The current study investigates sources of between-subjects variation in asymmetry scores on visual half-field and dichotic listening tasks. For each of these presentation modalities, subjects were given multiple laterality tasks. Results indicate that about 50% of the between-subjects variations in asymmetry scores in each modality is attributable to individual differences in perceptual asymmetries that are not stimulus-specific, referred to as "characteristic perceptual asymmetries" in this paper. In addition, the question of whether individual differences in characteristic perceptual asymmetries are modality specific, modality general, or both was investigated by entering subjects' asymmetry scores from visual half-field and dichotic listening tasks into a principal component analysis. The results of this analysis indicate that there are both modality specific and modality general influences on subjects' characteristic perceptual asymmetries.     

Looking at pictures but remembering scenes.

Ss tend to remember close-up photographs as having had extended boundaries (Intraub & Richardson, 1989). Three alternate explanations were tested: object completion, distortion toward a perceptual schema, and normalization toward a prototypic view. In three experiments, 55-130 undergraduates viewed 16 close-up, prototypic, or wide-angle views of objects for 15 s each. Immediately or 48 hr later, they rated test pictures on a 5-point scale as "same", "closer up", or "father away." Results ruled out object completion because boundary extension occurred when the picture contained no incomplete objects. Immediate tests supported the perceptual schema hypothesis because all unidirectional distortions involved boundary extension. Delayed tests were more suggestive of a memory schema effect because wide-angle pictures yielded boundary restriction. A two-component model of picture processing is proposed.