Inhibitory stimulus control and the magnitude of delayed reinforcement

The key pecking of pigeons was reinforced according to a variable-interval 1-min schedule during each of two successively presented stimuli. When the key was illuminated by a black line on a white background, reinforcement was delayed for 10 sec. When the key was illuminated by a plain white light, reinforcement was not delayed. For half of the subjects, the delayed reinforcer was 4.0-sec access to mixed grain, and for the remaining subjects it was 1.5-sec access. The immediate reinforcer was 1.5-sec access for all subjects. All subjects responded at a lower rate during the presentation of the black line; no between-group difference in terms of terminal response rate during the presentation of the line was found. However, subjects that received 4.0 sec of delayed reinforcement responded at a lower terminal rate during presentation of the plain white light than subjects that received 1.5 sec of delayed reinforcement. A subsequent generalization test along the line-orientation dimension produced flatter U-shaped gradients for subjects that received 4.0-sec of delayed reinforcement.     

The psychology of farming: A review of twenty-five years of research

If all of mankind is to have an adequate diet, we must both stabilize world population and increase markedly world food supply. Moreover, attaining any such increase in food supply may be as much a problem in vocational psychology (e.g. the skill, knowledge, openness to change, and motivation of farmers) as in agricultural technology. The purpose of this review is to further psychological work on agricultural productivity by listing and evaluating a cross-section of relevant articles since 1945. Because psychologists have largely ignored agriculture, most reviewed studies were conducted by other behavioral scientists. Studies are grouped according to three broad areas: (1) predictors of choice, success, and satisfaction; (2) adoption of recommended practices; and (3) communal agriculture.     

Aversive properties of the negative stimulus during learning with and without errors

In a successive discrimination four groups of pigeons were trained to discriminate between red and green. The groups differed with respect to the procedure used to introduce S?: Early-Progressive, Early-Constant, Late-Progressive, and Late-Constant. The aversive properties of S? were measured by an escape response in which a single peck at a second key terminated S? for 10 sec and darkened the chamber. The correlation between the aversive and error-producing properties of extinction was zero. More errors occurred when S? was introduced abruptly at a constant intensity while more timeouts from S? occurred when S? was introduced late. The procedure for introducing S? rather than the number of responses to S? appears crucial in determining how aversive S? becomes.     

Children's time perception as affected by order of stimulus presentation

Two groups of 5- to 6-yr.-old children estimated the time required to view 15 color slides containing an assortment of familiar objects. In one group, the pictures appeared in categorical order. A second group viewed the same 15 slides in a random order. The results showed that, although picture-recall was similar for the two groups, children in the category group estimated significantly longer durations than subjects in the random condition. The findings were discussed in the context of Ornstein's 1969 storage size hypothesis.     

Interpretation of homophones related to threat in anxiety states

In previous studies, we have established that anxiety states are characterized by an attentional bias that favors the processing of threatening stimuli. In the present study we extend this finding to ambiguous stimuli, specifically, homophones with spellings that correspond to either a threatening or a neutral meaning. As predicted, clinically anxious subjects used the threatening spellings relatively more than did controls, whereas recovered subjects were intermediate in this respect. Threatening words were associated with greater skin conductance responses than were neutral words, but the groups did not differ in their electrodermal reactions to homophones. We take these findings as evidence that, although the different meanings of ambiguous stimuli may be processed in parallel by all subjects, an interpretive bias operates such that anxiety-prone individuals tend to become preferentially aware of the more threatening meaning of such events.