Child performance on discrimination tasks: Effects of amount of stimulus variation

Two independently conducted studies investigated stimulus variation effects on children's discrimination learning. The stimuli in the first study were generated by a conjunctive rule and were presented in pairs. Mean trials to criterion was significantly lower for the single-feature change treatment (17.4) than for the multiple-feature change treatment (29.9). Single-feature change-treatment transfer scores were significantly higher only for stimuli that differed in terms of one of the features. The second study not only replicated the initial finding concerning the single-feature change treatment but also found that students made more errors in reaching criterion when stimuli were generated by an exclusive disjunctive rule and were presented singly. For all tasks, the single-feature change treatment with stimuli presented in pairs was accompanied by fewer errors to criterion than the other treatments.     

Behavioral inference in young children

Three experiments are reported on behavioral inference in children of 3 to 5 years of age. In each experiment the children learned two separate sequences of behavior which they were required to put together in the final test stage in order to obtain a reward. In the first experiment moderate levels of behavioral inference were obtained, although a relatively high proportion of children failed to respond in the test phase. In the second experiment different instructions were used in the test phase, the number of nonresponders was greatly reduced and a much higher proportion of children showed behavioral inference. The third experiment obtained similar results under conditions which excluded the possibility of mediation during a memory test, which was included in the previous experiments. It was concluded that behavioral inference is found, under suitable conditions, in children as young as 3-years-old, and that reports by other investigators of failure to find such inference up to the age of about 8 were due to problems with apparatus and instructions.     

Control of observing by antecedent stimuli

Five pigeons were run on a one-key discrete trials observing procedure. Trial onset was signaled by a white or yellow key light. Pecks in white or yellow intermittently produced S⁺ and S⁻, green and red key lights that signaled whether the trial would end with response-independent grain reinforcement or nonreinforcement. In the Redundant conditions, white and yellow were correlated with trial outcome, making S⁺ and S⁻ redundant. In the Informative condition, white and yellow were uncorrelated with trial outcome, so that S⁺ and S⁻ provided new information. During the Informative condition, all birds responded in the formerly positive, now uncorrelated color at higher rates than they did during the preceding or succeeding Redundant conditions, in which that same color was positively correlated with primary reinforcement. This result confirmed the prediction that an animal will observe at higher rates in the absence of reinforcement-correlated cues than in their presence.     

Behavioral contrast produced by a signaled decrease in local rate of reinforcement

Pigeons' key pecking in the presence of one stimulus (S1) was reinforced according to a response-dependent variable-interval schedule. Pecking rate during S1 increased (behavioral contrast) when a second stimulus (S2) [associated with either a response-dependent fixed-interval schedule (Experiment I) or a response-independent reinforcement schedule in which reinforcement availability was signaled by visual (Experiment II) or temporal (Experiment III) stimuli] alternated with S1. These experiments suggest that a discriminable, signaled decrease in local reinforcement rate during S2 is an antecedent of the behavioral contrast response rate increases during S1.     

A study of some conditions relating to the retarded adult's stereotyped responding in a binary-choice task

This study was a longitudinal one that examined the effects of certain conditions on alternation and perseveration in a binary-choice task. The conditions manipulated included: (1) lapse of time (stability of the pattern), (2) stimulus dissimilarity, (3) spatial location of the two alternatives, (4) time-out (time away from the task), (5) delay between responses, and (6) differential reinforcement of the two choices. Eight mentally retarded adults, identified as “pure” alternaters or perseveraters, served as subjects. Perseveration was “disrupted” only by differential reinforcement. Alternation was affected by all experimental manipulations with the exception of stimulus dissimilarity.