A two-stage detection model applied to skilled visual search by radiologists

Harvard Medical School and Peter Bent Brigham Hospital, Boston, Massachusetts 02115 The model treats the detection of targets in a visual search task as a concatenation of two serial detection stages. Preattentive visual mechanisms in the initial stage function as a filter, selecting specific features of a visual pattern for the observer’s explicit attention and final cognitive evaluation. The model uses bivariate normal distributions to represent the decision variables for the two serial stages, assuming different parameters for the target and nontarget features in a test set. The model is applied to the detection performance of radiologists interpreting chest x-rays under various conditions of search. It accounts for the substantial improvement in radiologists’ ability to distinguish between target and nontarget test features when they had to search the x-ray images, compared to their performance without visual search. A change in the ROC curve between two different search tasks could be interpreted as a shift in the selection cutoff used by the preattentive filter.     

Spatial frequency content of visual imagery

Three experiments employing the McCollough paradigm were conducted to determine the spatial-frequency content of visual imagery. In Experiment 1, large and reliable pattern-contingent color aftereffects were obtained after adaptation to visual imagery. The direction of the aftereffects indicated that subjects were adapting to higher spatial frequencies in their imagery. These results contrast with the data of Experiment 2, which demonstrate that color aftereffects obtained with adaptation to physically present stimuli are mediated by the fundamental spatial frequency components. The magnitude of the imagery-induced aftereffects in Experiment 1 equaled the magnitude of the externally induced aftereffects obtained in Experiment 2 with the same subjects. By blurring the to-be-imaged patterns (Experiment 3), the fundamental Fourier components became the salient perceptual features of the stimuli, and the direction of the imagery-induced aftereffects was reversed from that of Experiment 1, indicating that the spatial frequency content of the imagery had changed from higher to lower frequencies. Under normal viewing conditions, subjects use the higher spatial frequencies associated with the perceptually salient edges of stimuli to construct their images. The results of Experiments 1 and 3 are discussed in light of a current controversy over the nature of information representation in imagery, and it is concluded that support has been obtained for the analog model of visual imagery.     

The relationship of extraversion,neuroticism, and sensation-seeking to questionnaire-derived measures of nervous system properties

Five obliquely rotated factor analyses were performed on items from Eysenck and Eysenck’s (1975) EPQ, Zuckerman’s (1975) Sensation-Seeking Scale, and Strelau’s (1972) temperament inventory (STI), administered to 277 subjects (Ss). The analyses were used to examine the relationships between the personality dimensions E, N, L, P and Sensation-Seeking, which pertain mainly to social situations, attitudes and feelings, and questionnaire-derived measures of nervous system properties, which, while validated on experimental indices of nervous system properties derived from Nebylitsyn’s (1972) model, are expressed as characteristic features of social behavior, work style and activity. Four factors were identified—extraversion/strength of excitation/mobility; self-control of affect/stability/caution; strength of inhibition/verbal control/motor expressiveness/ nonmanipulativeness; and sensation-seeking/nervousness. The results offer support for Eysenck’s claim of some identity between excitatory strength and E, for the reported relationship between E and mobility, and for Eysenck’s conditioning postulate. They also suggest that similar temperamental variables underlie individual differences in both social and occupational/motor activity. Since Strelau’s STI items are validated on experimental indices of nervous system properties, it follows that typological characteristics may be inferred from questionnaire data derived from both behavioral categories.     

Intracranial cannulation of small animals

Special difficulties are encountered when attempting to provide intracranial cannulation of small animals that have floating or fragile skull bones. The technique described was developed for mice but seems applicable to other species. The cannula system is inexpensive and easy to use. A wound clip anchor seems superior to either skull screws or bonded acrylic, producing less damage to the brain and no necrosis of bone or tissue on the wound margin. Patency data up to 25 days is presented, and the system is as efficacious as other techniques.     

The role of proprioception in the perception and control of human movement: Toward a theoretical reassessment

The theoretical role of proprioception in the perception and control of human movement is elusive because of the obvious inability to manipulate experimentally the various receptive systems. Individuals who have had the metacarpophalangeal joint and joint capsule removed and replaced with silastic inserts afford a unique opportunity to evaluate a principal source of proprioception, namely, slowly adapting joint afferents. In a set of experiments, we show that such individuals show no deficits in finger localization following joint replacement. We take this and other complementary findings as a preliminary basis for proposing a dynamic rather than kinematic account of movement production. In addition, we provide a reconceptualization of the function of proprioceptive information in the CNS. Our arguments focus on proprioceptive inputs as tuning or modulating interneuronal pools rather than providing dimension-pecific information to the brain, as is commonly assumed.     

Coincidence anticipation of young normal and handicapped children

Two coincident-timing experiments examined the role of three different target velocities and display extents and three age levels of normal and retarded children. Subjects made a ballistic response to a target moving horizontally across their visual field. In the first experiment there were generally no clear differences between normal and retarded children on the task, with subjects having difficulty for both the slow and fast target speeds. In the second experiment, with target velocity held constant, no significant differences were reported between normal and handicapped children, although the longer the subjects were allowed to view the target the more accurate they were. The data were discussed in terms of the response strategies to perform anticipatory ballistic movements. An ecological issue was raised which suggested that children as well as adults make their most accurate anticipations when confronted with velocity problems that have been experienced in their everyday world.     

How and why people accept personality feedback

The present experiment examined a model and a supplementary explanation of feedback acceptance. The model consisted of inventory responding under a yea-saying response set and the explanation stated that feedback is accepted because it is accurate and persuasive. "Neurotic" and stable undergraduates (n = 120) took several personality inventories and then rated the accuracies of personality "interpretations." As predicted, the model mirrored every detail of feedback acceptance; also, the accuracy of interpretations related most simply to their acceptance and the undergraduates changed their self-perceptions in the direction of the interpretations. Contrary to predictions, individual differences in persuasibility did influence feedback acceptance.     

Some effects of lick-contingent delays on the development of schedule-induced polydipsia

Experiments 1 and 2 examined the effects of various durations of lickcontingent delays of reinforcement on the development of schedule-induced polydipsia. Food was provided every 1 min in the absence of licking. Delays of 1 min or more effectively disrupted the development of the licking behavior. In Experiments 3 and 4 a lick-contingent stimulus was provided in addition to the delay of food delivery. A light, which was turned on by a lick and turned off by food, greatly enhanced the development of polydipsia under delays that had previously prevented such development. A tone proved less effective than the light in promoting the development of polydipsia. Adventitious reinforcement and conditioned punishment explanations of these results were considered. A distinction was drawn between the mechanism responsible for the development of schedule-induced behavior and that responsible for its maintenance.     

Choice and reinforcement delay

Previous studies of choice between two delayed reinforcers have indicated that the relative immediacy of the reinforcer is a major determinant of the relative frequency of responding. Parallel studies of choice between two interresponse times have found exceptions to this generality. The present study looked at the choice by pigeons between two delays, one of which was always four times longer than the other, but whose absolute durations were varied across conditions. The results indicated that choice is not uniquely determined by the relative immediacy of reinforcement, but that absolute delays are also involved. Models for concurrent chained schedules appear to be more applicable to the present data than the matching relation; however, these too failed to predict choice for long delays.