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Three pigeons performed on two‐component multiple variable‐interval variable‐interval schedules of reinforcement. There were two independent variables: component duration and the relative frequency of reinforcement in a component. The component duration, which was always the same in both components, was varied over experimental conditions from 2 to 180 sec. Over these conditions, the relative frequency of reinforcement in a component was either 0.2 or 0.8 (±0.03). As the component duration was shortened, the relative frequency of responding in a component approached a value equal to the relative frequency of reinforcement in that component. When the relative frequency of reinforcement was varied over conditions in which the component duration was fixed at 5 sec, the relative frequency of responding in a component closely approximated the relative frequency of reinforcement in that component. That is, the familiar matching relationship, obtained previously only with concurrent schedules, was obtained in multiple schedules with a short component duration.

A method of measuring thresholds in animals is described and illustrated in the case of flicker fusion in the budgerigar. After training with reinforcement for pecking at a high‐frequency light (115 Hz) and nonreinforcement for pecking at a low‐frequency light (20 Hz), subjects were given threshold trials and reinforcement trials mixed randomly in equal number. In threshold trials (no reinforcement), the target began flashing at 115 Hz and decreased in flash rate with each peck until the subject stopped responding. During reinforcement trials, the target continued to flash at 115 Hz, and responses were reinforced on a variable‐ratio schedule. Flicker thresholds obtained from two birds showed a linear relation to the logarithm of intensity in accordance with the Ferry‐Porter law.

Pre‐delinquent peers in Achievement Place (a community based family style rehabilitation program based on a token economy) were given points (token reinforcement) to modify the articulation errors of two boys. In Experiment I, using a multiple baseline experimental design, error words involving the /l/, /r/, /th/, and /ting/ sounds were successfully treated by both a group of peers and by individual peers. Also, generalization occurred to words that were not trained. The speech correction procedure used by the peers involved a number of variables including modelling, peer approval, contingent points, and feedback. The individual role of each of these variables was not experimentally analyzed, but it was demonstrated that peers could function as speech therapists without instructions, feedback, or the presence of an adult. It was also found that payment of points to peers for detecting correct articulations produced closer agreement with the experimenter than when they were paid points for finding incorrect articulations. The results were replicated in a second experiment with another subject who had similar articulation errors. In addition, the second experiment showed that peer speech correction procedures resulted in some generalization to the correct use of target words in sentences and significant improvements on standard tests of articulation.

Children enrolled in a Head Start program were instructed to describe the contents of each of four boxes of toys. After the subject's initial description (baseline), the experimenter (model) described the contents of three boxes of different toys in alternation with the subject's descriptions. For one group, the experimenter used descriptive adjectives in his descriptions. In a second group, the experimenter used no adjectives of any kind. A marked increase in the frequency of descriptive adjectives was observed during the first description after modeling in the first group. This increase was maintained in successive descriptions at approximately the frequency used by the experimenter. Frequency of descriptive adjectives remained at zero or decreased in the scond group.

Pigeons were trained on a non‐spatial delayed alternation task in which the color not pecked on the previous trial was correct. When varying delays were interposed between trials, alternation accuracy decreased as a function of delay, but remained greater than chance with a 45‐sec delay. Successful alternation on the longer delays was accomplished without behavioral mediation of the delay intervals. Also, during initial testing when a position cue was available in addition to the color cue after incorrect trials, alternation accuracy was greater after a preceding incorrect trial than after a correct trial. When the position cue was removed, no differences occurred as a function of the outcome of the preceding trial.

Observing behavior of two squirrel monkeys was examined under a multiple schedule of four components. Lever (observing) responses produced either a stimulus indicating the availability of food or another stimulus indicating food was not available. Key responses in the presence of the food‐available stimulus produced food on a continuous reinforcement schedule. In the absence of food‐available stimuli, responding on the key had no scheduled consequences. Observing responses produced food‐available stimuli according to three different random‐interval schedules with mean interstimulus availability times of 1, 2, and 4 min. In the fourth component of the multiple schedule (observing extinction) food‐available stimuli never occurred. Each component of the schedule was correlated with a distinctive auditory stimulus. Observing rates decreased with decreasing frequency of the food‐available stimulus. Observing rates during extinction continued decreasing when the brief stimulus indicating food unavailability was no longer produced by lever pressing. When the brief stimulus was reinstated response rates increased abruptly.

Pigeons were trained on a trial procedure. A trial began with the illumination of a pecking key by a white light. After a fixed interval, a key peck could turn the key to one of two equi‐probable colors and produce a delayed trial outcome—an equi‐probable occurrence of either reinforcement or nonreinforcement. After a trial, the key turned dark and the trial ended. The response could be made into an observing response by correlating the key colors with the outcomes. Response rates in the fixed interval then increased to a level greater than when the colors and outcomes were uncorrelated. In another phase, the response produced only the colors. The trial outcomes occurred some seconds after the fixed interval without a response being required. Correlating the colors with the outcomes again increased response rates. In a second experiment, a further condition was added in which reinforcement was the outcome on every trial. Response rates were lower than when there were equi‐probable reinforcement and nonreinforcement outcomes with correlated colors, and about the same as when there were equi‐probable outcomes with uncorrelated colors. The results suggest that stimuli providing information about the probability of reinforcement are themselves reinforcing.

Twelve pigeons were given successive discrimination training involving variable‐interval reinforcement for key pecking in the presence of one intensity of monochromatic light randomly alternated with extinction for pecking during another intensity. All of the pigeons were then tested in extinction for generalization along the intensity dimension, and all showed a displacement of maximal responding from the positive stimulus in the direction opposite the negative stimulus. For six of the pigeons, for which the test included only three values beyond the positive stimulus, four showed peaked gradients but two did not, showing monotonic gradients with maximal responding to the most extreme test value. For another six pigeons tested over a wider range, all showed peaked gradients. Thus, when a sufficiently wide range of test values is employed, generalization gradients for visual intensity have the same peaked form as do gradients for qualitative visual dimensions such as wavelength or line angle.