Are rats short-sighted? Effects of stimulus distance and size on visual detection

Behavioural evidence concerning short-sightedness in rats is apparently conflicting: in some experiments rats have performed poorly with visual stimuli further than about 60 cm distant, while in others they have made efficient use of more distant cues, for example to find their way through mazes. However, in the experiments suggesting short-sightedness, the physical size of the stimuli was not varied, so that stimulus distance and visual angle were confounded. In the present experiment, therefore, the size and distance of the stimuli to be detected were varied independently. Over the range tested (30-160 cm), distance was found to produce relatively slight effects on the smallest detectable visual angle, and these tended to diminish with practice. Thus, no good evidence was found for short-sightedness in rats up to 160 cm, a finding consistent with current views of the structure and image-forming capacities of the rat's eye. The smallest detectable targets were, however, surprisingly large in view of the rat's visual acuity (which is about 1c/deg): at the distances tested, animals required considerable training to run reliably to targets subtending less than 5-10° of visual angle. Difficulties in responding to stationary stimuli of this size are likely to restrict severely the use that rats make of vision both in the laboratory and in their natural surroundings.     

Student Response to Three Types of Orientation Programs

A high proportion of positive responses was obtained from students who participated in three different types of pre-college orientation programs. Small group approaches consistently elicited more favorable responses than assemblies or large groups. Greater faculty involvement resulted in participants' noting an increased academic emphasis. Participants believed they had benefited in some way from programs which varied considerably as to length, activities, organization, and purposes.     

Dimensions of affective experience in three age groups.

The dimensions by which adults of differing ages experience emotion were studied by self-administering questionnaires administered to older adults (n = 828) recruited from Elderhostel programs, middle-aged (ages 30-59) children of Elderhostel attenders (n = 231), and young adult (ages 18-29) subjects recruited from college classes or through Elderhostel participants (n = 207). Elders were higher in emotional control, mood stability, and emotional maturity through moderation and leveling of positive affect and lower in surgency, psychophysiological responsiveness, and sensation seeking. These findings are consistent with the hypothesized increase in self-regulatory capacity with age. These cross-sectional differences cannot, however, be distinguished from cohort-related explanations; they require considerable replication across different types of subjects and further characterization of the dimensions in terms of their functions for self-regulation.     

Visual and tactual form discrimination: Psychophysical comparison within and between modalities

Intermodal perceptual equivaience was investigated, using visual and tactual oddity discrimination and cross-modal matching-to-sample tasks. Four groups of Ss were presented with 100 problems made up of randomly derived forms from five levels of sidedness. The same quadratic relationship was observed for all tasks as a function of complexity, with optimal performance at eight sides. Comman information utilization, as indicated by intercorrelations of performance variables and by correlational analyses with differences in form measures, was not as pronounced within side classes. Evidence concerning the nature of pattern-feature usage in discrimination was obtained from graphical analyses.     

Managing Conflict in Dutch Organizations: A Test of the Relevance of Deutsch's Cooperation Theory1

Deutsch's theory of cooperative and competitive conflict may be usefully extended to Dutch people. Results of LISREL analyses on data collected from interviews of Dutch employees in 2 companies indicate that competitive goals interfered with the open, constructive discussion of opposing views. However, cooperative goals were not found to contribute to constructive controversy. Dutch who discussed their opposing views openly made progress on the task, worked efficiently, and strengthened their work relationship and their confidence in future collaboration. These results do not argue that Dutch and North Americans handle conflict similarly, for how these groups operationalize the theory may differ significantly. Goal interdependence may have the potential to be a framework for promoting conflict management between Dutch and North Americans.     

College Counseling: Union and Intersection

College counseling can best be understood as the intersection of a professional activity and an environment. The specialty has developed from the merging of several movements: vocational guidance, mental health, and student personnel work. These elements are reflected in the diversity of backgrounds and perspectives represented by college counselors and in differing models of counseling services. College counseling will be affected by trends including health care reform, scarcity of resources in higher education, changing student demographics, and complex societal issues.     

A study of neuropsychological impairment among school-indentified learning-disabled students

This investigation examined the proportion of school-identified learning-disabled (LD) students who scored in the impaired range on the Halstead Reitan Neuropsychological Battery for Children (HNBC) over a 20-year period. A difference was noted in findings for periods before and after the passage of federal legislation (Public Law 94-142); specifically, the proportion of LD students who scored in the impaired range on neuropsychological tests was significantly higher prior to than after this law. A similar pattern of impaired performance across the different tests was noted before and after the legislation. The implications of these results for theorists and practitioners are discussed.     

Tasks and timing in the perception of linguistic anomaly

Three experiments were conducted to investigate the relative timing of syntactic and pragmatic anomaly detection during sentence processing. Experiment 1 was an eye movement study. Experiment 2 employed a dual-task paradigm with compressed speech input, to put the processing routines under time pressure. Experiment 3 used compressed speech input in an anomaly monitoring task. The outcomes of these experiments suggest that there is little or no delay in pragmatic processing relative to syntactic processing in the comprehension of unambiguous sentences. This narrows the possible explanations for any delays that are observed in the use of pragmatic information for ambiguity resolution.The research reported in this paper was supported by Program Project Grant HD-01994 to Haskins Laboratories from the National Institutes of Child and Human Development, and in part by a grant to Stephen Crain and Donald Shankweiler from the University of Connecticut Research Foundation. We thank Jacques Mehler and Gerry Altmann for helpful information about speech compression algorithms. We are especially grateful to Ignatius Mattingly for his generous expert advice on speech compression and design of the experimental materials, and also for recording all the speech stimuli. Julie Boland, Brian McElree, Janet Nicol, and Martin Pickering provided very helpful advice on an earlier draft.     

Many-Valued Logic and Event-Related Potentials

In previous experiments on event-related potentials (ERPs) during linguistic judgments, the subjects' decisions have been categorical (e.g., true vs false). In this experiment, more realistic variations in truth value and subject certainty were used. Thirty-eight naive undergraduates read a story about a fictional murder. ERPs were recorded as the subjects rated the strength of their beliefs about statements relating to suspects in the crime. Because no subject was sure which of the suspects was guilty of committing the crime, binary (true–false) category judgments were inappropriate. Three components of the ERP waveforms were affected by the experimental manipulations. An early positive component was largest to sentences concerning the suspect considered most likely to have committed the crime. A subsequent broad posterior positivity (LPC) also showed significant sentence-type differences, but it was larger to sentences considered probable—whether they were true or false—than to more ambiguous sentences. A third ERP component (N400) was negative at midline electrode sites and peaked at approximately 420 ms. Subjects' truth-value judgments had no effect on the N400. N400 was, however, affected by the subject's task. It was more negative when subjects made graded judgments about truth value than when they made binary true–false judgments. Overall, naturalistic judgments of sentence validity produced a variety of brain responses that reflected different aspects of linguistic decision making.