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Pigeons' key pecks were brought under the control of the duration of a visual stimulus in one‐key and two‐key procedures. In the one‐key procedure, pecks were reinforced after presentations of a long‐duration stimulus but not after presentations of a short‐duration stimulus. In the two‐key procedure, left‐key pecks were reinforced after the long‐duration stimulus and right‐key pecks after the short‐duration stimulus. In both procedures, the long‐duration stimulus was 10 sec, and the short‐duration stimulus was increased from 1 to 8 sec in 1‐sec steps. Discriminative control developed with both procedures, but with greater accuracy in the two‐key procedure, in which a difference threshold was obtained at short‐duration values between 7 and 8 sec, or about 2.5 sec shorter than the long‐duration stimulus.

Five fifth‐grade students tutored five kindergarten children in basic arithmetic skills for 7.5 weeks. A control group consisted of five kindergarten children who received no tutoring and were matched with the experimental group in arithmetic ability. Pre‐, mid‐, and posttesting was done using a skills‐based arithmetic test. Results showed that the experimental group made far greater gains than the control group on a post‐test comparison (matched pairs signed ranks test p = 0.062). In addition, a subanalysis of specific arithmetic skills showed they were improved only when tutoring for that skill was carried out. Systematic observations made of the tutor‐student interactions indicated wide tutor‐to‐tutor variability in the percentage of student responses praised, and very little use of negative, disapproving statements. It was concluded that trained fifth‐grade students can effectively teach basic arithmetic skills to kindergarteners.

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Key‐peck responses of two pigeons were maintained on variable‐interval schedules of food reinforcement in the presence of a stuffed pigeon to study the characteristics of attack induced by that schedule. The mean interval of the schedule was increased from 15 sec to 600 sec in eight steps before an intermediate interval was reintroduced. The principal characteristics of attack were: (1) substantial attack first occurred on a variable‐interval schedule of 90 sec in one pigeon and at 180 sec in the other, (2) the highest attack rates occurred on variable‐interval schedules of 300 sec and 600 sec, (3) attack rate generally increased to a maximum and then decreased to a lower level across sessions at each schedule, (4) attacks developed a postreinforcement locus across the initial sessions on all schedules and, except on variable‐interval schedules of 300 and 600 sec, occurred primarily in the postreinforcement period during extended training, (5) attack rates and key‐peck rates were not recovered when the intermediate‐length schedules were reintroduced, and (6) attack rate and key‐peck rates were negatively correlated. Except for the fact that the maximum attack rates occurred at interfood intervals of 300 and 600 sec, and that attack and key‐peck rates were negatively correlated, these findings have counterparts in experiments with other reinforcement schedules.

The learning by hungry pigeons of a discrimination between two successively presented compound visual stimuli was investigated using a two‐key autoshaping procedure. Common and distinctive stimulus elements were simultaneously presented on separate keys and either followed by food delivery, S+, or not, S—. The subjects acquired both between‐trial and within‐trial discriminations. On S+ trials, pigeons pecked the distinctive stimulus more than the common stimulus; before responding ceased on S— trials, they pecked the common stimulus more than the distinctive one. Mastery of the within‐display discrimination during S+ trials preceded mastery of the between‐trials discrimination. These findings extend the Jenkins‐Sainsbury analysis of discriminations based upon a single distinguishing feature to discriminations in which common and distinctive elements are associated with both the positive and negative discriminative stimuli. The similarity of these findings to other effects found in autoshaping—approach to signals that forecast reinforcement and withdrawal from signals that forecast nonreinforcement—is also discussed.