Brightness interactions between rods and cones

Two parafoveal test targets with different spectral compositions were matched in brightness to a fixed-luminance foveal reference target under scotopic adaptation conditions. The idea of the experiment was to find a reference luminance for which one of the matching test targets stimulated only rods while the other stimulated both rods and cones. If brightness was proportional to the linear sum of rod and cone responses, then the luminance of the matching rod+cone target would be predictably closer to rod threshold than would that of the rod target. The results were complicated by evidence that rod responses to the test targets selectively enhanced weak chromatic signals. Nevertheless, it was possible to show that cone activity never reduced the matching luminance as much as predicted by the additivity hypothesis, and sometimes even increased it. These findings suggest that cone activity can suppress brightness signals from rods.     

The effect of object shape and mode of presentation on judgments of apparent volume

Apparent volume for geometric solids and life-sized two dimensional representations of these solids was scaled by magnitude estimation. Data were adequately fit by power functions whose exponents were less than those previously reported for judgments of apparent length and area. Object shape and mode of presentation affected both magnitude estimations of apparent volume and the best fitting power function exponents. The influence of shape, both across object shape classes and within the cylinder shape class, appears to depend upon the relative elongation of the vertical dimension.     

On unpredictability as a causal factor in “learned helplessness”

In two replications, two groups of dogs were exposed to a series of uncontrollable, electric shocks. For one group the shocks were preceded by a tone (i.e., Paired). For the other group the shocks were randomly related to the tones and hence unpredictable (i.e., Random). Each replication also included a third group; in the first it was exposed only to the series of tones (CS-only), while in the second, it was exposed only to a series of shocks (Shocks-only). Then, all dogs were required to learn a discriminative choice escape/avoidance task in which the required response was to lift the correct paw in the presence of each of two visual S^Ds to escape or avoid the shocks [($\text{S}{}_1{}^{\mathrm{D}}\text{?R}{}_1\text{)}\text{(S}{}_2{}^{\mathrm{D}}\text{?R}{}_2$)]. Dogs preexposed to random tones and shocks were least successful in learning the task relative to those groups which experienced either predicted shocks, only the tones, or only the shocks, which in turn did not differ from each other. These results permitted the inference that the proactive interference with choice behavior following random tone CSs and shocks was attributable to a learned irrelevance generalized with respect to CSs.     

Pavlovian conditioned stimulus effects upon instrumental choice behavior are reinforcer specific

In a transfer-of-control experiment with rats, Pavlovian CSs were tested for the specificity of their effects. The instrumental behavior consisted of a discriminative, conditional two-lever choice task in which qualitatively different appetitive reinforcers were contingent upon the two correct choices. In a Pavlovian phase, subjects experienced conditioning to establish either a CS⁺ or CS^? for one reinforcer or a CS⁺ or CS^? for the other reinforcer. Finally, in a test, these CSs were presented when there was the opportunity to make choice responses. The CS⁺s evoked choices of the lever which had eventuated in the reinforcer that had served as the Pavlovian US, while the CS^?s showed only a slight tendency to evoke the other choice responses. When the CSs were compounded with the original S^Ds, the CS⁺s had little effect upon the vigor of responding while the CS^?s reduced the vigor of responding to the S^D for the reinforcer that was the same as the US used in establishing the CS^?. The results are discussed in terms of associative mediational theory and the reinforcer specificity of Pavlovian conditioned excitation and inhibition.     

Programmed stuttering therapy for children: Comparison of four establishment programs

Four different establishment programs (programmed traditional, delayed auditory feedback, pause, and gradual increase in length and complexity of utterance) for improving the fluency of school-age children who stutter were compared. The programs were carried out by eight public school clinicians with 16 children (eight elementary and eight junior-senior high school) in their respective schools. All four programs produced important improvement in the speech fluency of the 16 children. All the children demonstrated transfer of fluency to extratraining settings. The delayed auditory feedback program required the least therapy hours, but it was difficult for the clinicians to operate correctly. The gradual increase in length and complexity of utterance programs produced the best overall results. The transfer and maintenance programs provided for additional generalization and permanency of fluency. Follow-up revealed that the children continued their increased level of fluency.     

Interpersonal Reactions to Depression and Physical Disablllty In Dyadic Interactions1

Examined the interpersonal responses of persons engaged in dyadic interactions with confederates who enacted either depressed or socially appropriate roles and appeared either with or without a physical disability. Subject negative evaluations of confederates were indirectly obtained from a thought-listing measure. The overt behaviors of subjects were surreptitiously recorded on videotape and measures of verbal and nonverbal behavior were acquired. Subjects spoke less to the depressed targets and had significantly higher rates of negative evaluations of these persons. In addition, subjects gazed less at the depressed confederates. These effects were not moderated by target physical appearance. Findings are discussed as they relate to social models of depression and the stigmatizing effects of disability.     

Spatial and conjoint models based on pairwise comparisons of dissimilarities and combined effects: Complete and incomplete designs

In pairwise multidimensional scaling, a spatial representation for a set of objects is determined from comparisons of the dissimilarity of any two objects drawn from the set to the dissimilarity of other pairs of objects drawn from that set. In pairwise conjoint scaling, comparisons among the joint effects produced by pairs of objects, where the objects in a pair are drawn from separate sets, are used to determine numerical representations for the objects in each set. Monte Carlo simulations of both pairwise dissimilarities and pairwise conjoint effects show that Johnson's algorithm can provide good metric recovery in the presence of high levels of error even when only a small percentage of the complete set of pairwise comparisons are tested.