Ratio responding as a function of concurrent avoidance schedules, yoked shocks, and ratio value

Fixed-ratio food-reinforced responding in rats was studied alone and with concurrent shock avoidance or with concurrent response-independent shocks matched to those that occurred in the avoidance condition. Under each condition, fixed-ratio size was increased over successive daily sessions. Fixed-ratio response rate generally passed through a maximum as a function of fixed-ratio size. Decreased fixed-ratio responding at values beyond the maximum occurred when (1) the time to complete a fixed ratio approximated the response-shock interval of the avoidance schedule, (2) the shock rate increased, and/or (3) the ratio requirements were so high that ratio strain occurred. Avoidance rates decreased slightly as fixed-ratio size increased.     

Within-session changes in responding during concurrent schedules with different reinforcers in the components.

Rats and pigeons responded on several concurrent schedules that provided different reinforcers in the two components (food and water for rats, Experiment 1; wheat and mixed grain for pigeons, Experiment 2). The rate of responding and the time spent responding on each component usually changed within the session. The within-session changes in response rates and time spent responding usually followed different patterns for the two components of a concurrent schedule. For most subjects, the bias and sensitivity to reinforcement parameters of the generalized matching law, as well as the percentage of the variance accounted for, decreased within the session. Negative sensitivity parameters were sometimes found late in the session for the concurrent food-water schedules. These results imply that within-session changes in responding could cause problems for assessing the validity of quantitative theories of concurrent-schedule responding when the components provide different reinforcers. They question changes in a general motivational state, such as arousal, as a complete explanation for within-session changes in responding. The results are compatible with satiation for, or sensitization-habituation to, the reinforcers as explanations.     

Programmed Instruction: Construction Responding, Discrimination Responding, and Highlighted Keywords

Skinner (1958) expressed the need for an increase in the effectiveness and efficiency of education. In particular, he suggested that programmed instruction could provide such efficiency. The present study used a within-subject design to compare the effects of four types of instructional materials; those requiring overt construction responses, overt discrimination responses, covert reading of text with highlighted key words, and covert reading of standard text. The materials requiring overt responding produced greater learning than did the covert reading materials, with or without highlighting. There was no difference found between the two types of overt responding; nor were there differences between the two types of covert reading materials. Thus, this study supports the assumption that overt responding is more effective. However, the overt response materials also required proportionately more time. Therefore, this showed no benefit of overt responding in terms of efficiency.     

Failure to loose fear: The impact of cognitive load and trait anxiety on extinction

Exposure therapy is an effective technique for fear reduction. However, whether effective exposure requires attentional allocation to the feared situation remains a debated clinical issue. In the present study, the impact of attention allocation in extinction was investigated in an experimental conditioning study. Through a between-subjects manipulation of cognitive load, we created a condition in which participants could allocate their attention to the feared stimulus during extinction (low load condition), and a condition in which attentional allocation was impaired (high load condition). The influence of cognitive load on extinction was examined by comparing electrodermal responses and verbal ratings for the conditioned stimuli in the two extinction load conditions. The results show less successful extinction in the high load condition than in the low load condition. However, this effect was found only in low anxious participants, and it was prominent only on the skin conductance responses. The present results suggest that extinction is not automatic but requires cognitive resources.     

Behavioral contrast of time allocation

Pigeons' standing on a platform produced food reinforcement according to two-component multiple schedules in which either both components consisted of the same variable-interval schedule or one of these was replaced with a component without reinforcement (extinction). The components of the multiple schedule alternated every 30 sec, and were signalled by changes in the color of diffuse overhead illumination. Changing the schedule of one of the components to extinction increased the percentage of time spent on the platform during the unchanged component (behavioral contrast). This result casts doubt on accounts that attribute behavioral contrast to variations in the rate of noninstrumental elicited responses.     

Elicited responding to signals for reinforcement: the effects of overall versus local changes in reinforcement probability

Pigeons were studied on a three-component multiple schedule where all reinforcement was independent of responding. Two components were cued by different keylights and were associated with different rates of reinforcement. The third was always a no-key period associated with extinction. After a few sessions, pecking was elicited by the keylights signalling the reinforcement and continued to be maintained indefinitely. The duration and sequence of the three components were varied to determine if the primary controlling variable was differences in the overall probability of reinforcement, or if it was the immediate change in reinforcement signalled by the onset and/or offset of the stimulus. Both variables were found to control behavior. When 30-sec components were used, the primary controlling variable was the overall probability of reinforcement, but when 3-min components were used, overall probability had little effect. Control by local changes in reinforcement also occurred, although the type of local control varied both across subjects and experimental conditions. Some behaviors were controlled more by the change in reinforcement signalled by the onset of the stimulus, while others were controlled more by the change signalled by the offset of the stimulus.