Visual gap and offset discrimination and its relation to categorical identification in brief line-element displays

Visual processing was investigated in judgments of relative line position. Stimulus continua were generated by bisecting a straight line and displacing the segments. Experiment 1 measured discrimination of pairs of longitudinally displaced segments at equal steps along the continuum. At long (2 s) durations discrimination fell smoothly, but at short (100 ms) durations it was sharp-peaked. In Experiment 2 the short-duration stimuli were labeled with subsets of the labels no gap, just a gap, and more than just a gap. Theoretical discrimination performances were computed and the one based on no gap and just a gap closely fitted observed performance. Experiments 3 and 4 were similar to 1 and 2, with lateral replacing longitudinal displacement. Similar "categorical" performance was obtained. It was concluded that there are discrete mechanisms for early detection of relative line position and that 2 labels can be used to characterize performance in each direction.     

Sequential response effects in the white rat during conditioning and extinction on a DRL schedule,

Sequential IRT data were obtained for three rats on a DRL 60-sec reinforcement schedule. It was found that first-order sequential dependencies exist under this schedule, including the partial dependence of the length of any given IRT on the length of the preceding IRT. The sequential analysis also served to extend the finding in the literature, based on frequency distributions, that the likelihood of a reinforced IRT is greater after a reinforced IRT than a non-reinforced IRT. Rapid extinction and reconditioning were obtained.     

Modifications of the Poggendorff effect as a function of random dot textures between the verticals

In the present research, we investigated the modification of the strength of the Poggendortf illusion as a function of different densities ofrandom dot textures failing the space between the verticals. The results ofExperiment 1 show that the illusory effect is a nonlinear function ofthe texture parameterr, the ratio of black pixels to white and black pixels, with a minimum forr=0.5, approximately, and a maximum forr=0 andr=1. The results may be interpreted by an analytical model of perceptual space dynamics, in which the effect dependson the amount of interaction between points of different light intensity. A computer simulation performed by applying the analytical model to different values ofr shows a good agreement between the predictions and the experimental data. To test the hypothesis underlying the model, a second experiment was carried out to measure the magnitude of the expansion ofthe space between the verticals as a function of the parameterr. The results are consistent with the hypothesis of the model. The overall data are discussed in terms of their implications on various theories proposed for the Poggeadorff illusion.     

The role of vocabulary ability during visual word recognition in younger and older adults

The role that vocabulary ability plays in adult age differences in word recognition was investigated. In Experiment 1, 44 older adults (ages 61-93 years) were compared with 44 younger adults (ages 18-39 years) on a standard lexical-decision task, with ambiguous words, unambiguous words, and pseudowords serving as stimuli. In Experiment 1, the Wechsler Adult Intelligence Scale-Revised (WAIS-R; D. Wechsler, 1981) vocabulary performance was uncontrolled across the younger and older adults, and the older adults had higher WAIS-R scores. There was no Group x Stimulus interaction. In Experiment 2, the data from the same 44 older adults were compared with data from a new sample of 44 younger adults (ages 18-44). Both groups were then matched on WAIS-R performance. Results revealed a significant Group x Stimulus interaction. Reaction time differences between the younger and older groups on the ambiguous words and unambiguous words were identical. The differences in reaction times for words and pseudowords were greater in the older adults. The importance of vocabulary ability during word recognition and lexical processing is discussed.     

Executive Functioning and Delay Discounting of Four Different Outcomes in University Students

The study investigated a potential relationship between level of executive functioning and rates of delay discounting (i.e., the subjective decrease in the value of an outcome if its delivery is delayed). University students completed an executive-functioning questionnaire and then a delay-discounting task involving four different outcomes (money, cigarettes, dating partner, body image). Results showed that the overall measure of executive functioning was a significant predictor of rates of discounting of three of the four outcomes, and approached significance for the fourth outcome. Further, different subscales of executive functioning were significantly correlated with discounting of different outcomes. These results suggest that executive functioning plays a role in discounting of delayed outcomes and that procedures designed to affect either executive function or delay discounting might result in concomitant changes in the other measure.