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Reinforcement was introduced for responses normally treated as errors in signal‐detection procedures. The first experiment used a standard two‐response discrete‐trial procedure with no reinforcement for errors. Results showed that rats altered their response biases but maintained constant sensitivity to visual signals when reinforcement probabilities varied, and that their sensitivity depended on the physical difference between signals, in accordance with the predictions of signal‐detection theory. Experiment II, with rats, and Experiment III, with pigeons, demonstrated that sensitivity decreased in this procedure when reinforcement was scheduled for errors with the signals held constant, despite independence of overall number of reinforcers and sensitivity. Experiment IV, with rats, replicated the decrease in sensitivity in a continuous procedure employing only one response. The decrements in sensitivity were similar across Experiments II, III, and IV, and accorded well with earlier research. Thus, contrary to a fundamental assumption of signal‐detection theory, estimates of sensitivity are not always invariant with respect to the outcomes of responding, but depend on relative reinforcement of correct responses.

Differential reinforcement of other behavior (DRO) and noncontingent reinforcement were compared as control procedures during the modification of a 3‐yr‐old preschooler's compliance. The recorded reinforcer was teacher proximity (within 3 ft (0.9 m) of the subject for at least 5 sec) which was often accompanied by positive verbal comments that varied in content across experimental conditions. The verbal content during contingent reinforcement might have been: “Thank you for picking up the blocks”; during noncontingent reinforcement: “You're wearing a pretty dress”; and during DRO: “I don't blame you for not picking up because it isn't any fun”. Contingent reinforcement increased compliance in all manipulation conditions. Noncontingent reinforcement decreased compliance during two reversal conditions. However, the behavior was variable and did not decrease to the low levels reached during the two DRO reversals.

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In a discrete‐trial choice situation, 12 pigeons were trained to discriminate which of two different fixed ratios they had completed. Psychometric functions were obtained at three ratio requirements (i.e., with the larger ratio set at 10, 20, or 30 responses) by gradually reducing the size of the smaller value. Although different response biases developed across subjects, in each case accuracy decreased systematically with ratio difference regardless of absolute ratio requirements. Above‐chance performances were maintained even at relative ratio differences of 10% or less. Estimates of the Weber fraction showed that, in general, discriminability improved with absolute ratio size up to 30 responses, and beyond, when the results of other studies are considered. A similar trend held for rats studied by other investigators in fixed‐ratio “counting” tasks at lower requirements. In terms of a signal‐detection analysis, performance was similar to that reported for other species and dimensions. Taken together, the results suggest that for this somewhat novel dimension the same psychophysical relations hold as are commonly observed for exteroceptive stimuli.

In order to examine therapists' discriminative responding to normal and idiosyncratic patient responses, naive subjects were presented with a simulated “patient” for treatment. The subjects were made to believe they were reinforcing normal verbalizations emitted by this patient In fact, they were listening to a tape on which normal and idiosyncratic verbalizations had been recorded. Different probabilities of normal and idiosyncratic “patient” verbalizations could be presented to the subjects by means of a digital programming unit. In one of a number of conditions, the subjects' accurate reinforcing responses were followed by an increased probability of the patient's normal verbalizations. Accurate reinforcing responses emitted by the subjects were brought under the control of normal and idiosyncratic patient responses, by use of contingent feedback, change in patient responding, and monetary reinforcers. When the patient's normal verbalizations increased in probability, so did the subjects' accurate reinforcing responses following the patient's normal verbalizations, and to a lesser degree, the subjects' inaccurate reinforcing responses following the patient's idiosyncratic verbalizations. When the patient's idiosyncratic verbalizations increased in probability, the subjects' accurate and inaccurate reinforcing responses decreased in probability. The clinical implications of these tendencies are discussed.

Four pigeons were exposed to a series of two‐component multiple schedules of reinforcement that ordinarily yield positive and negative behavioral contrast. The stimuli that signalled the component schedules were sometimes located on the response key and sometimes off. Positive behavioral contrast was observed only when the stimuli were on the key. Negative contrast was observed independent of stimulus location. These data suggest that positive and negative contrast may be causally unrelated, and support an account of contrast in terms of the summation of key pecks that are separately controlled by response‐reinforcer and stimulus‐reinforcer dependencies.

Three adult female elephants (Elephas maximus) were tested on a light‐dark discrimination problem with an 8‐yr intertrial interval. The first subject took only 6 min to reach criterion and made only two errors, suggesting remarkable retention. The other two subjects were found to have visual anomalies that would have gone undetected without this research.

The common assumption that employing tangible rewards with individual children will have adverse effects upon peer observers was studied in the preschool setting. Multiple‐subject, multiple‐baseline procedures were applied to two classes of children, aged 3.5 to 6 yr. In each group, three consecutive children with low base rates of in‐seat behavior received a verbal contingency and food rewards for sitting, while peers (with either low or high rates of in‐seat behavior) received neither food nor teacher attention for sitting. Peer reactions measured were in‐seat behavior, aggression, nonaggressive disruptive behavior, and complaints. The procedures neither decreased the in‐seat behavior of peer observers, nor increased their aggressive or disruptive behavior. On the contrary, peers with low base rates of sitting initially displayed an abrupt, but temporary, increase in sitting. Moreover, although no compensatory attention was delivered, all children exhibited improved sitting by the end of the study. Complaints, which consisted mainly of requests for rewards, decreased in frequency with successive program phases, and within each phase. It is suggested that the class improvement in sitting behavior and the absence of negative effects on observers may be partially due to the high frequency of attention the teacher maintained for other desired behavior and the lack of attention to children's complaints.

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