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.     

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.     

Goal-performance relations: The effects of initial task complexity and task practice

The current study was conducted to examine the effects of task complexity and task practice (trials) on the goal-performance relationship. Specific, difficult goal assignments were predicted to enhance performance on a complex task only in later task practice. On a simpler task, specific, difficult goal assignments were predicted to enhance performance in early task practice and to disrupt performance in later task practice. The results indicated that goals exerted the predicted effects in the simple task version but had no effect in the complex task version. Possible relationships between amount of task practice and stages of skill acquisition are discussed for tasks differing in complexity. The results are also discussed in terms of cognitive resource demands and self-regulatory processes. Implications for the effectiveness of goals in relation to task complexity and task trials are also discussed.This article is based on the senior author's dissertation at the University of Minnesota. We thank Milt Hakel, Allan Jones, and Bart Osburn for their helpful comments on earlier drafts. The authors also wish to thank Phil Ackerman and John Campbell for their insightful comments throughout the research project and other members of the dissertation committee: Rich Arvey, Mark Davisson, and Marvin Dunnette.This research was partially supported by the Air Force Office of Scientific Research Project LAMP, under the auspices of the Air Force Human Resources Laboratory (contract AFOSR-87-0234) and by a Research Initiation Grant from the University of Houston.Portions of this data were presented at the American Psychological Association Meetings, Atlanta, 1988.     

Quantitative and qualitative analyses of clock drawings in Alzheimer's and Huntington's disease.

Although visuoconstructive impairment has been reported in both Alzheimer's (DAT) and Huntington's (HD) disease, there is little knowledge concerning how this cognitive deficit differs quantitatively and qualitatively in these two progressive dementias. To address this issue, the present study compared performances on the Clock Drawing Test (CDT: command and copy) of 25 DAT patients, 25 equally demented HD patients, and 25 elderly normal controls (NC). In the command condition, both patients groups were significantly impaired compared to the NC group. Although there was no significant difference between DAT and HD patients' total quantitative scores, a qualitative error analysis revealed a number of dissociations between the two patient groups. Graphic difficulties, very common in HD patients, were virtually absent in DAT patients; in contrast, conceptual errors were almost exclusively seen in DAT patients and were related to the severity of their dementia. Perseveration and "stimulus-bound" responses were also more frequent in DAT patients, and both groups made visuospatial errors. In the copy condition, the DAT, but not the HD, patients evidenced a marked improvement in performance. These results indicate that while both DAT and HD patients have significant visuoconstructive difficulties even in the early stages of their disorders, the specific cognitive processes underlying their quantitative impairments are quite different. It is possible that the DAT patients' conceptual errors are yet another indicator of the deterioration of their semantic knowledge.     

Remembering pictures: pleasure and arousal in memory.

Incidental memory performance for pictures that varied along the affective dimensions of pleasantness and arousal was assessed. For both an immediate and delayed (1 year later) free-recall task, only the arousal dimension had a stable effect on memory performance: Pictures rated as highly arousing were remembered better than low-arousal stimuli. This effect was corroborated in a speeded recognition test, in which high-arousal materials encoded earlier in the experiment produced faster reaction times than their low-arousal counterparts. Pleasantness affected reaction time decisions only for pictures not encoded earlier. These results suggest that whereas both the dimensions of pleasantness and arousal are processed at initial encoding, long-term memory performance is mainly affected by arousal.     

Developmental expression of defensive responses during exposure to conspecific adults in preweanling rats (Rattus norvegicus).

I examined preweanling rats' (Rattus norvegicus) expression of ultrasounds and secretion of ACTH when exposed to unfamiliar adult male rats or to their mothers. Pups at 7 days of age produced similar levels of ultrasonic vocalization near both unfamiliar males and mothers. However, these pups could discriminate familiar from unfamiliar adults because ACTH was significantly higher in pups near adult males than in those near mothers. At 14 days of age, pups avoided adult males but not their mothers; therefore, adult males represented a significant threat. Importantly, 14-day-old rats significantly reduced ultrasound production only when near adult males. Pups at 21 days of age no longer emitted ultrasounds when socially isolated or when near conspecific adults. In addition, 14- and 21-day-old rats produced similar elevated ACTH levels across stimulus conditions. Results show significant changes in preweanling rats' responses to conspecific adults.     

Components of analogical reasoning in a mildly head injured population

This study sought to investigate the effects of mild head injury on a particular type of cognitive ability, verbal analogical reasoning. The performance of 19 individuals with head injuries was compared to a group of 30 control subjects matched for age, education, and gender on 100 verbal analogies. Solution times and error rates were modeled. Unstandardized regression weights for individual subjects were correlated with subjects’ performance on a number of standardized ability tests. Results showed that compared to the control subjects, the head injured subjects: (a) were significantly slower to solve the analogies, and were particularly slow to perform certain processes: encoding/inference and comparison; (b) tended to show greater variability in performance; and (c) had data that had a poorer componential model fit. The data suggest that analogical reasoning is affected by a head injury, and that certain information processes may be responsible for performance deficits.     

Spatial cognition and neighborhood use: the relationship in older adults.

Measures of spatial cognition, neighborhood knowledge, and neighborhood use from the research described by Walsh, Krauss, and Regnier (1981) were examined to determine if laboratory tests of spatial cognition were significant predictors of older adults' use of their neighborhoods. The overall results show that laboratory-based measures of spatial cognition and subjects' knowledge of their neighborhoods are both significant predictors of their use of neighborhood goods and services. The ability to learn and remember the location and orientation of objects, when contextual cues were not provided at test, was more predictive of the participants' neighborhood use than either the participants' number of years in the neighborhood or their mobility. Spatial memory as measured by the Educational Testing Service Building Memory task predicted neighborhood knowledge, which was predictive of neighborhood use.     

Beliefs about condoms and accessibility of condom intentions in Hispanic and African American youth

The construct accessibility model (CAM) holds that constructs are most likely to influence behavior when they are accessible in memory. While the theory of reasoned action sees intention as an important determinant of behavior, the CAM predicts that the intention to act upon a given health behavior is not likely to be acted upon unless the intention is in an accessible state. Therefore, people who frequently talk about or think about using condoms are likely to have condom related constructs available and use them when needed. This paper reports findings from the pilot phase of a project to identify beliefs which influence condom use in Hispanic and African-American youth living in Detroit. 15 male and 15 female Hispanics and 17 male and 17 female African-Americans aged 15-21 years of mean and median age 18.5, were interviewed face-to-face in 1989 with the goal of identifying condom beliefs which may influence their condom use. 80-82% of male participants, 53% of Hispanic females, and 100% of Black females had experienced sexual intercourse, with age at first intercourse ranging between 13.1 and 16.5 years. 88% of Black women and 7% of Hispanic women were pregnant at the interview. Regarding participants' level of preventive knowledge, all but 1 recently immigrated Hispanic female knew HIV was transmitted by needles and sexual intercourse. 87% of Hispanics and 94% of African-Americans responded that condoms protect against AIDS, but only 13% of Hispanics and 47% of African-Americans knew that nonlatex condoms do not. Some participants expressed concern that condoms reduce sensitivity and/or break during intercourse. Controlling for sexual activity, 25% of Hispanic females, 83% of Hispanic males, 71% of African-American females, and 80% of African-American males had ever used a condom; no Hispanic and 14% of Blacks reported using them consistently in the 12 month period preceding the interview. With 100% of African-American males and 97% of Black females reporting thinking about using condoms compared to 80% of Hispanics, the study findings suggest that condom intentions are more accessible in African-Americans than among Hispanics.