An evaluation of the reliability of probability judgments across response modes and over time

Despite the importance of probability assessment methods in behavioral decision theory and decision analysis, little attention has been directed at evaluating their reliability and validity. In fact, no comprehensive study of reliability has been undertaken. Since reliability is a necessary condition for validity, this oversight is significant. The present study was motivated by that oversight. We investigated the reliability of probability measures derived from three response modes: numerical probabilities, pie diagrams, and odds. Unlike previous studies, the experiment was designed to distinguish systematic deviations in probability judgments, such as those due to experience or practice, from random deviations. It was found that subjects assessed probabilities reliably for all three assessment methods regardless of the reliability measures employed. However, a small but statistically significant decrease over time in the magnitudes of assessed probabilities was observed. This effect was linked to a decrease in subjects overconfidence during the course of the experiment.     

A comparison of Guided Imaginal Coping and imaginal exposure in the treatment of panic disorder

The present study evaluated the efficacy of a new intervention, Guided Imaginal Coping (GIC), compared to imaginal exposure (IEX), and a waiting-list control (WLC) condition among 24 clinic outpatients meeting DSM-III-R criteria for panic disorder (PD) or PD with agoraphobia. GIC was the more consistently effective intervention, with individuals demonstrating significant improvement in frequency and severity of panic attacks (Pas) as well as significant reductions in physiological and subjective arousal to provocative imagery. Individuals in the IEX intervention demonstrated less consistent improvement on the dependent measures, while individuals in the WLC condition essentially remained unchanged. Both GIC and IEX were effective according to a composite measure of clinically significant improvement. However, only GIC was superior to the WLC condition when clinical improvement was defined as zero PAs at follow-up. These findings, while preliminary, suggest that GIC can be added to the armamentarium of effective approaches to treating PD.     

Utility maximization and melioration: Internalities in individual choice

How do people go about choosing between alternatives in relatively simple settings? This study explores some of the variables that past work suggests may be relevant. Volunteer subjects worked for money in six procedures in which the probability of a payment from either of two alternatives was 1.0, but the rate of pay (i.e. the speed with which a payment was delivered or the size of the payment) interacted with the subjects recent allocation of choices, which we define as the ‘internalities’. Because of the internalities, choosing the currently more profitable alternative did not maximize total earnings. Subjects were more likely to fail to maximize when the interaction between present pay and past choices was spread over longer sequences of choices, or when the reward variable was the speed, rather than the value, of each payment. Subjects often disregarded the internalities and were instead guided by the current yields of the two alternatives, which is a frequently observed tendency, called ‘melioration’, in experiments on choices by animals. The tendency toward melioration was only partially counteracted by explicit instructions on how to maximize earnings. We discuss a theoretical framework for melioration that postulates both motivational and cognitive sources.     

Self-Monitoring negative statements

We examined the effects of a self-monitoring program on reducing the frequency of negative statements of a student with mild mental retardation who was enrolled in a self-contained classroom at a middle school. A changing criterion design was used within a multiple baseline design across two classroom periods. Additionally, the frequency of positive statements was reported. The results showed a decrease in the number of negative statements, and an increase in the number of positive statements. Maintenance data collected up to 8 weeks after the program ended indicated that the student continued to emit positive rather than negative statements. The use of this procedure to decelerate undesirable behavior is discussed.     

Potentiation of the pressor response to stress by tolbutamide in dogs

Tolbutamide has previously been shown to amplify the pressor effects of “exogenous” catecholamines in conscious dogs, possibly due to sensitization of the α₁-adrenoreceptor-mediated vasoconstriction. The objective of this study was to examine if tolbutamide also amplifies the pressor effects of “endogenous” catecholamines released during psychological stress (classical Pavlovian aversive conditioning). Experiments were conducted in β-adrenoreceptor-blocked (propranolol, 1 mg/kg, i.v.) conscious dogs (n=4) trained in classical aversive conditioning. Conditioning was accomplished by following a tone (CS+) with a 1/2 second shock; another tone (CS-) was not followed by any shock and served as control. With saline pretreatment, aversive conditioning (i.e., CS+) increased mean arterial pressure (MAP) only by approximately 4.7% when compared to CS-, whereas with tolbutamide (45 mg/kg, i.v.) pretreatment, the increase in MAP induced by CS+ beyond what was induced by the CS- (approximately 6.2%) was significantly (p<0.05) larger than that with saline pretreatment. In isolated canine femoral arterial segments (n=4), the vasoconstrictor effect of phenylephrine (an α₁-agonist) at 5×10^?6M (which was the EC₅₀ value) was amplified by 2×10^?2M of tolbutamide from 54.0±2.0% to 66.9±2.1%. In conclusion, tolbutamide amplifies the pressor effects of “endogenous” catecholamines in conscious dogs, possibly by sensitization of the α₁-adrenoreceptor-mediated vasoconstriction. This mechanism of action is novel and has not been reported with other agents.     

Shape from stereo: A systematic approach using quadratic surfaces

We used quadratic shapes in several psychophysical shape-from-stereo tasks. The shapes were elegantly represented in a 2-D parameter space by the scale-independentshape index and the scale-dependentcurvedness. Using random-dot stereograms to depict the surfaces, we found that the shape of hyperbolic surfaces is slightly more difficult to recognize than the shape of elliptic surfaces. We found that curvedness (and indirectly, scale) has little or no influence on shape recognition.     

Tensorial basis to the constancy of perceived object extent over variations of dynamic touch

Subjects wielded occluded rods, with or without attached masses, and reported the distances reachable with their distal tips. Experiments 1–3 compared wielding about the wrist, the elbow, and the shoulder. Experiments 4 and 5 compared free wielding, using the whole arm, with wielding only about the wrist. The two comparisons, respectively, were of spatial and temporal variations in the rod’s rotational inertia. Perceived extent was found to be constant in both comparisons. This constancy was tied to the inertia tensorI _ij defined about a point that remains a fixed distance from the object during wielding&#x2014;an invariant of the spatially and temporally dependent patterning of mechanical energy impressed upon the tissues of the body. Discussion focused on the reciprocal action and perception capabilities of multisegmented limbs, the tensorial relations in the neurobiology of dynamic touch, and the strategy of understanding perceptual constancy through invariants.     

Limits of focused attention in three-dimensional space

The present experiment examined the shape of the attentional gradient in three-dimensional space. Subjects performed a response-compatibility task in which they were instructed to respond to a centrally located target and ignore flanking distractors. The irrelevant distractors were presented at combinations of seven different depths, three different horizontal separations, and three different vertical separations relative to the target. Depth was varied in a stereoscopic display viewed through polarized glasses. Overall, the size of the response-compatibility effect decreased with increased separation in all three dimensions. Interestingly, the response-compatibility effect was larger for horizontal separations than for vertical separations and was larger for crossed disparities than for uncrossed disparities. The results suggest an elliptical focus of attention, with steeper gradients in the vertical dimensions than in the horizontal dimensions. In addition, the results suggest, along the vertical dimension, a steeper gradient for objects located beyond the focus of attention relative to that for objects located between the observer and the focus of attention.