Discrimination and generalization by rats of temporal stimuli lasting for minutes

In three experiments, rats learned to respond differentially to reinforced and nonreinforced trials when the length of the intertrial interval (ITI) predicted the trial outcome (reinforcement or nonreinforcement). Rats in control groups, for whom the length of the ITI did not predict the outcome, did not show differential performance on nonreinforced and reinforced trials. Generalization gradients obtained following discrimination training were comparable to those obtained following discrimination training with other types of discriminative stimuli. That is, groups which had shown differential performance in discrimination training yielded generalization gradients with fastest speeds at the previously reinforced ITIs, slowest speeds at the previously nonreinforced ITIs, and intermediate speeds at ITIs of intermediate length. Control groups yielded flat gradients across all ITIs tested. These effects were shown for relative time discrimination (short time = reinforcement, long time = nonreinforcement, or the reverse) and also for an absolute time discrimination (long and short time = reinforcement, middle time = nonreinforcement or the reverse). This method was effective for time duration measured in minutes rather than seconds, as is more commonly the case.     

Depth separation and the Ponzo illusion

The Ponzo illusion refers to an apparent change in length of objectively equal parallel lines induced by enclosure within an acute angle. The present study investigated this illusory change in stimulus extent as a function of the relative depth positions of the parallel lines and the inducing angle. To permit facile and unconfounded manipulation of apparent depth, the stimuli comprising the Ponzo configuration were stereoscopic contours formed from dynamic random-element stereograms. The main results were: (1) apparent depth separation exerted a strong influence on illusion magnitude; (2) this influence was asymmetrical in that illusion magnitude decreased when the inducing angle appeared in depth behind the parallel lines and increased when the inducing angle appeared in depth in front of the lines. These data are consistent with a general theory of space perception that assumes that information about depth position is processed prior to information about stimulus characteristics.     

Activity of wrist muscles elicited during imposed or voluntary movements about the elbow joint

To examine the coordination of muscles during multijoint movement, we compared the response of wrist muscles to perturbations about the elbow joint with their activation during a volitional elbow movement. The purpose was to test the following two predictions: (a) Responses can occur in muscles not stretched by the perturbation, as has been reported for other multijoint systems; and (b) the motor pattern in response to a perturbation mimics an opposing volitional motor pattern across the two joints. We recorded the electromyographic (EMG) activity of elbow and wrist muscles as well as the flexion/extension motions at the elbow and wrist joints during individual trials that either involved a response to a torque perturbation that extended the elbow or required volitional elbow flexion. The results of this study confirmed that responses were elicited in the nonstretched wrist muscles when the elbow joint was perturbed. The same motor sequence of elbow and wrist flexors was present for both the volitional and perturbation task (with the forearm supinated), regardless of whether the wrist joint was immobilized or freely moving. The findings suggest that the nervous system relies on the purposeful coupling of elbow and wrist flexors to counter the inertial effects during the unrestricted voluntary movement, even though the coupling does not appear to be purposeful during the perturbation or with the wrist immobilized. The coupling of elbow and wrist flexors, however, was not rigidly fixed, as evidenced by muscle onsets that adapted over repeated perturbation trials and a reversal of the wrist muscle activated (wrist extensor) when the forearm was pronated. Hence, the coupling of muscle activities can be modified quantitatively when not beneficial and can be altered qualitatively with different initial configurations of the arm.     

Manifest needs of prospective counselors: a comparative study

Mean performances of 81 prospective counselors on each of the Edwards Personal Preference Schedule (EPPS; Edwards, 1959) needs were analyzed and statistically compared with performances of elementary school counselors, other school counselors, urban college students, professional women, Roman Catholic sisters, and the 1959 EPPS norm samples. Performances of the men and women in the prospective counselor group were similar. Men had a significantly higher need for achievement and dominance, but the significance did not reach .01. Two EPPS needs, intraception and nurturance, consistently differentiated the prospective counselor group. Comparisons across samples indicated that prospective counselors were most similar to the two counseling samples and, for the female subgroup of prospective counselors, to the sample of professional women. Largest across-sample differences were found between the female prospective counselors and the Roman Catholic sisters, between the female prospective counselors and norm samples of female college students and female adults, and between the male prospective counselors and the male adult norm sample.     

Mothers and fathers of young children: comparison of parenting styles

This study compared the developmental expectations and parenting behaviors of 52 mothers and fathers with children between the ages of 1 and 4 years, using the Parenting Inventory: Young Children. While both mothers and fathers were nurturing parents, mothers obtained significantly higher nurturing scores. Possible reasons for this difference were discussed. Developmental expectations and discipline strategies did not differ between mothers and fathers.     

Intelligence and race: further comments on J. P. Rushton's work.

A review of some implications of J.P. Rushton's 1988 and 1990 work on racial differences in brain mass (size or weight) suggests that his comments do not constitute a viable scientific theory.     

Manual discrimination of force using active finger motion

In these experiments, two plates were grasped between the thumb and forefinger and squeezed together along a linear track. An electromechanical system presented a constant resistance force during the squeeze up to a predetermined location on the track, whereupon the force effectively went to infinity (simulating a wall) or to zero (simulating a cliff). The task of the subject was to discriminate between two alternative levels of the constant resistance force (a reference level and a reference-plus-increment level). Results of these experiments indicate a just noticeable difference of roughly 7% of the reference force using a one-interval paradigm with trial-by-trial feedback over the ranges 2.5≤F _o≤10.0 newtons, 5≤D≤30 mm, 45≤S≤125 mm, and 25≤V≤160 mm/sec, whereF _o is the reference force,D is the distance squeezed,S is the initial finger-span, andV is the mean velocity of the squeeze. These results, based on tests with 5 subjects, are consistent with a wide range of previous results, some of which are associated with other body surfaces and muscle systems and many of which were obtained with different psychophysical methods.     

Factors affecting entrapment in escalating conflicts: The importance of timing

Entrapping conflicts are those in which individuals continue to invest their resources—even in seemingly losing propositions-in large part to justify previous unfilled expenditures. It has been demonstrated that individuals define their motivation for investing very differently at the various stages of an entrapping conflict. One implication of this motivational dynamic is that various factors may differentially affect degree of entrapment (i.e., amount invested), depending upon the point in time at which they are introduced. The present studies were designed to test this notion. All subjects were given an initial monetary stake and had the opportunity to win more by taking part in an entrapping investment situation. In Experiment 1, half the subjects were provided with a payoff chart that made salient the costs associated with investing (Highcost salience condition) whereas half were not (Low-cost salience condition). Moreover, for half of the subjects the payoff chart was introduced before they were asked to invest (Early condition) whereas for the other half it was introduced after they had invested a considerable portion of their resources (Late condition). Entrapment was lower in the High salience-Early than in the Low salience-Early condition. However, there was no difference between groups in the Late condition. In Experiment 2, the perceived presence of an audience interacted with personality variables related to face-saving to effect entrapment. When the audience was described as “experts in decision making,” subjects high in public self-consciousness (or social anxiety) became less entrapped than those low on these dimensions. When the audience consisted of individuals who “wished simply to observe the experimental procedure,” however, high public self-consciousness (or social anxiety) individuals were significantly more entrapped than lows. Moreover, these interaction effects occurred when the audience was introduced late, but not early, into the entrapment situation. Taken together, these (and other) findings suggest that economic factors are more influential determinants of behavior in the earlier stages of an entrapping conflict, whereas face-saving variables are more potent in the later phases. Alternative explanations are discussed.     

An automated eye movement laboratory for on-line electrooculography

This paper describes an automated eye movement laboratory that uses electrooculography (EOG) to study people’s eye movements while they read. An on-line minicomputer processes bioelectric potentials that correspond to saccadic eye movements. Horizontal saccades larger than 1.5 deg of visual angle are detected and analyzed in real-time as they occur. The laboratory is designed for prolonged yet unobtrusive observation of human eye movements during sustained reading periods of minutes or hours. All important functions regarding data collection and data reduction are performed automatically, according to simple procedures that can be applied uniformly and without bias to nearly all subjects that we study. Results from three experiments are cited in order to quantify the performance of the laboratory with respect to four criteria: saccade detection accuracy, measurement accuracy, sensitivity, and the uniformity of these measures over different subjects.     

TASK-RELEVANT CONTROL IN ORGANIZATIONS1

Studies of organizational power using questionnaire measures of perceived control have usually asked respondents, “How much influence do (various groups in the hierarchy) have on what goes on in your organization?” The present study measured such general control, plus control over specific task-relevant responsibilities. Data were obtained from 526 individuals at four hierarchical levels in 20 regional offices of an insurance company. Predicted relationships between total general control and task-relevant control and an independent measure of effectiveness were only partially supported. The general manager's control was more important than expected. However, measuring task-relevant control could be a useful management tool, and could help future research explicate relationships between control and effectiveness.