Cross-task validation of functional measurement

Ss judged average heaviness of two unseen lifted weights on a 20-step rating scale. They also rated heaviness of a single visible object of variable size and weight. The data for each task obeyed the parallelism prediction of the linear integration model. This within-task consistency validates jointly the model and the response scale. Functional measurement procedure yielded independent scales of subjective heaviness from each task. These were linearly related, a criterion of external consistency. The plot of subjective heaviness against objective weight was slightly negatively accelerated. These results disagree with those that have been obtained with magnitude estimation. Since the rating data satisfy both internal and external consistency, they constitute the true measure of sensation. Magnitude estimation, in contrast, must be biased and invalid.     

Effect of “backward” masker fringe on the detectability of pulsed diotic and dichotic tonal signals

The effects of backward masker “fringe” on performance in homophasic and antiphasic masking conditions were investigated. The results of the study indicate that (1) the presence of a backward masker fringe has only a small effect on performance in homophasic masking conditions; (2) under antiphasic masking conditions, the presence of a backward masker fringe improves performance; (3) similar to the results of studies investigating the effects of forward masker fringe, the magnitude of the improvement in performance increases as the duration of the fringe increases; and (4) the magnitude of the improvement caused by the presence of backward masker fringe is considerably smaller than the magnitude of the improvement caused by the forward masker fringe. It appears, then, that the presence of backward masker fringe may provide a baseline or reference phase similar to that which the forward fringe is presumed to provide. The presence of this reference phase after the offset of the signal apparently makes the phase shift associated with the signal-plus-noise waveform more discernible, thus leading to higher detectability. However, for reasons not yet clear, the presence of a baseline or reference phase after the offset of the signal (backward fringe conditions) does not make the signal-plus-noise phase shift as discernible as do either the presence of that same reference phase before the onset of the signal (forward fringe condition) or the presence of that same reference phase both before signal onset and after signal offset (continuous masker condition).     

Some differences among figural aftereffects,apparent motion,and paracontrast*

It has been suggested that figural aftereffects, apparent motion, and paracontrast may be produced by very similar or equivalent processes. The empirical functions relating figural aftereffect to the duration of the inspection figure and the interfigural distance are significantly different from the corresponding apparent motion and paracontrast functions. The functions relating paracontrast to the interstimulus interval are significantly different from the corresponding figural-aftereffect and apparent-motion functions. Thus, it is unlikely that the processes underlying the three phenomena are the same. Researchers who attempt to study feature analyzers in the human visual system should consider using more than one dependent variable, since none of the three phenomena contains all of the available information. Within-Ss designs should be avoided because a strong response bias exists between figural-aftereffect and apparent-motion tasks.     

Some effects of interreinforcement time upon choice

Pigeons' responses were reinforced on two identical and concurrently available chain variable-interval-schedules. Unlike the typical concurrent chains procedure, both links were operative throughout, thus producing three types of concurrency: (1) concurrent initial links; (2) concurrent initial and terminal links; (3) concurrent terminal links. Choice proportions in each of these three states suggested that the pigeons were sensitive to momentary likelihoods of reinforcement: choice proportions for a schedule were higher when the schedule had been operative for some time, resulting in a higher probability of reinforcement. The study also showed that the relative rates of responding did not match the relative rates of reinforcement in any of the three states of concurrency. Instead, the choice proportions in both the concurrent initial and in the concurrent terminal links were intermediate between the scheduled and the obtained relative rates of reinforcement, while the choice proportions for a terminal link concurrent with an initial link consistently overmatched the relative interreinforcement times (and were typically 1.00). These data indicate that an accurate characterization of choice may not be obtained by considering only the relative interreinforcement interval where one interreinforcement interval is segmented into a chain. Instead, the organism's choice for a schedule will be substantially lowered by the chaining operation.     

Inverse relation between choice and local response rate with a schedule of response-produced blackouts

Pigeons were exposed to a two-key concurrent chains schedule in which identical frequencies and distributions of food presentations generated different response rates in the terminal links. An inverse relation between local rate of response in the terminal links and relative frequency of response in the initial links was observed. The high response rate was produced in one terminal link by a second-order schedule in which responding produced brief blackouts of the response key. Responding under the same schedule in the other terminal link did not produce blackouts. Under initial training and after spatial reversal of the terminal-link schedules, two of three pigeons had lower relative frequencies of response in the initial member of the chain with the higher terminal link response rate. The third pigeon showed no change in preference at reversal.     

Two temporal parameters of food postponement

Rats were trained to press a lever under schedules of food postponement. In the absence of lever presses, food was delivered periodically (food-food interval). Responses initiated a second interval (response-food interval) that was reset by each additional response. Performance was first studied at different response-food intervals with the food-food interval fixed at 30 or 60 sec, or 10 min. Response-food intervals were examined in ascending order and then recovery was studied at shorter intervals. Finally, the food-food interval was manipulated with response-food interval fixed at 30 sec. At food-food intervals of 30 and 60 sec, responding first increased and then decreased as the response-food interval increased. At the 10-min food-food interval, responding decreased with increasing response-food interval. In general, very low rates of responding occurred when the response-food interval was 60 sec or more and when it equalled or exceeded the food-food interval. However, responding was maintained in one animal when the food-food interval was decreased from 120 to 15 sec with the response-food interval at 30 sec. Results, in terms of several dependent variables, are compared with data on shock avoidance. Effects of response-independent and response-produced food and shock are discussed.     

Probability learning as a function of momentary reinforcement probability

Pigeons were trained on a probability learning task where the overall reinforcement probability was 0.50 for each response alternative but where the momentary reinforcement probability differed and depended upon the outcome of the preceding trial. In all cases, the maximum reinforcement occurred with a “win-stay, lose-shift” response pattern. When both position and color were relevant cues, the optimal response pattern was learned when the reinforcement probability for repeating the just-reinforced response was 0.80 but not when the probability was 0.65. When only color was relevant, learning occurred much more slowly, and only for subjects trained on large fixed ratio requirements.