Orientation effects on line afterimages

Lines of various orientations were viewed as prolonged afterimages in six experiments. The duration of unitary appearance was not influenced by line orientation for monocular afterimages, but there was a marginal effect for afterimages generated binocularly; vertical and horizontal lines tended to be visible for longer than did 45-deg lines. Measures of fragmentation frequency and the latency to the first disappearance did not vary reliably with orientation under any conditions. Binocular afterimages lasted longer than did monocular ones, but generally showed the same pattern of fragmentations. These results are compared with those from experiments using optical stabilization and steady fixation, in which orientation differences have been reported.     

Averaging: An empirical validity criterion for magnitude estimation

Ss judged grayness of neutral value Munsell chips under two response conditions: magnitude estimation and graphic rating. In addition, they judged average grayness of pairs of chips under the same two response modes. The averaging data were evaluated in terms of a simple model for subjective averaging. The graphic rating data fitted the model, but the magnitude estimates showed consistent discrepancy. It was concluded that the Ss were averaging, but that magnitude estimation distorted their judgments.     

Transfer of responses to open and closed shapes in discrimination learning by cats

Two sets of 32 cats each were matched for performance in learning to discriminate an open and a closed shape and were then trained on a transfer task. The consistent groups were rewarded for choosing the same class of shape (open or closed) in learning and transfer. The inconsistent groups were rewarded for choosing the open figure in one task and the closed figure in the second, or vice versa. After learning the transfer task, all of the Ss relearned the original discrimination task under the same conditions that prevailed in initial training. The inconsistent groups made more errors on both the transfer and retention problems; both these differences were significant at the 0.1% level of confidence. These results and those obtained on preference tests support the hypothesis that cats classify shapes as open or closed in terms of perimeter and number of sides.     

Fixed-ratio performance under conditions of delayed reinforcement

Four rats were trained on a schedule in which completion of a fixed number of lever presses initiated a signalled delay period, at the end of which food was delivered. Lever presses made during the delay had no scheduled consequences. Delays of 12, 3, and 0.75 sec were used, and it was found that the latency of the first response after food (the post-reinforcement pause) increased with length of delay. There was, on the other hand, no consistent effect of delay upon rates of responding after the post-reinforcement pause.     

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.     

Sustained behavioral contrast in children

Children were exposed to a multiple schedule involving equal variable-interval schedules in each of two components and a multiple schedule involving a variable-interval schedule in one component and an extinction schedule in the other. Response rates were equal in both components when each involved a variable-interval schedule. Response rates differed in the two components of the multiple variable-interval extinction schedule. Response rates were higher in the variable-interval schedule when the accompanying schedule was extinction than when it was variable interval. The increase in response rate in the variable-interval component, simultaneous with the decrease in response rate in the extinction component, illustrated sustained behavioral contrast, and was the first evidence of this phenomenon in children.     

Lever attacking by rats during free-operant avoidance

Rats pressed a lever to avoid shock on a free-operant avoidance schedule. Some subjects were also exposed to extinction in which the response-shock contingency was eliminated while the shock-shock contingency remained in effect. A specially constructed lever was used that registered not only presses, but also biting attacks on the lever. Throughout various phases of the study, shocks often elicited lever biting as well as post-shock responding. The results suggested that shock-elicited attacks that are forceful enough to activate the operandum might account for some of the responding that occurs in experiments on free-operant avoidance behavior. In particular, shock-elicited operandum attacking might account for post-shock response bursting during free-operant avoidance and the extreme persistence of responding sometimes noted when shocks are delivered during the extinction of avoidance behavior. To the extent that this is true, these phenomena should not be characterized as operant behavior in interpreting the results of experiments on free operant avoidance.     

Maintenance and suppression of responding under schedules of electric shock presentation

In squirrel monkeys previously trained under a continuous avoidance schedule, characteristic patterns of responding were maintained under a 3-min variable-interval schedule of shock presentation (response-produced shock). Responding in the presence of a periodically presented stimulus, the termination of which coincided with the delivery of a response-independent electric shock (Estes-Skinner procedure), was not reliably affected. When shocks followed every response during certain signalled portions of the session, and were presented under the variable-interval schedule during the rest of the session (multiple 1-response fixed-ratio, 3-min variable-interval schedule of shock presentation), responding was suppressed during the fixed-ratio component and maintained during the variable-interval component. Environmental consequences do not have immutable properties, and may either support or suppress behavior, depending on the schedule of presentation.