Indexador

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Acquisition of a sound localization discrimination by rats was investigated. Two loudspeakers were located outside an experimental enclosure containing two levers and a dipper feeder. In the same‐side condition, responses on the lever nearest the sound‐producing speaker were reinforced. Animals in this condition acquired the discrimination rapidly, generally within the first session. In the opposite‐side condition, responses on the lever furthest from the sound‐producing speaker were reinforced. Acquisition for animals in this condition began below the chance level (50% correct responses) and took on the order of 10 sessions to approach the final, high level. The course of acquisition in both cases appeared to depend upon an initial tendency of rats to respond on the lever nearest the source of sound in this situation. The rise‐decay time of the 4‐kHz tone burst signal clearly affected the performance level reached. It did not, however, affect the rate at which the discrimination was acquired.

Changes in response rate similar to frustration effects were studied in a two‐lever situation. Responding on one lever on a fixed‐interval schedule produced access to water for 5 sec and an exteroceptive stimulus. In the presence of this stimulus, responding on another lever on a fixed‐interval schedule produced access to water for 5 sec and terminated the stimulus. Occasional omission of a previously scheduled reinforcer after responding on the first lever resulted consistently in increases in rate on the second lever during the immediately succeeding interval. In another procedure, occasional presentation of a previously unscheduled reinforcer after responding on the first lever resulted consistently in decreases in rate on the second lever during the immediately succeeding interval. Changes occurred after the first omissions or presentations and were about the same in magnitude as the procedure continued over several sessions. Typically, an increase or decrease in rate was maintained throughout an entire 100‐sec interval. Changes in rate on the second lever of approximately the same magnitude also occurred when rate on the first lever was near‐zero under a schedule that differentially reinforced behavior other than lever pressing.

Pigeons were exposed to concurrent fixed‐interval and variable‐interval schedules of food reinforcement on two keys. The times between reinforcement were varied systematically on both keys. The overall relative frequency of responding on the fixed‐interval key depended on the relative frequency of reinforcement, but did not match it. Instead, the ratio of responses on the fixed‐interval key to responses on the variable‐interval key was a power function of the ratio of reinforcements, with an exponent of 0.5. Patterns of responding between reinforcements on the fixed‐interval key depended on both relative and absolute values of the reinforcement schedules. Similar overall relative responding was obtained at different absolute schedule values with equal relative reinforcement, despite some differences in patterns of responding.

A generalized discrimination of /er/ and /est/ suffixes as labels for stimuli exemplifying comparative or superlative relationships was established in three institutionalized retardates through differential reinforcement. The subjects were first taught correct pointing in response to opposite adjectives (e.g., “big—small”) presented as labels for simple visual stimuli, and then taught each of the comparatives, or each of the superlatives possible for those opposites (e.g., “big—bigger” and “small—smaller”, or “big—biggest” and “small‐smallest”). As training proceeded, novel combinations of the training stimuli were presented as unreinforced probes to display any developing generalization of the training. As training of comparative discrimination proceeded, correct pointing response to comparative probes was high, but correct response to superlative probes was low. When training of superlative discriminations replaced training of comparatives, correct response to superlative probes increased, and correct response to comparative probes remained high.

A severely retarded resident was released from a timeout chair only occasionally for brief periods of time. Under the timeout contingency alone, the subject made a choke response within minutes of being released. Attention, such as hugs, smiles, and candy was then increased, first by providing it non‐contingently and continuously as long as there were no aggressive responses and then, by making it contingent upon incompatible responses. Under conditions of timeout plus increased attention, choking decreased abruptly. Grabbing responses, which increased when choking was reduced, were also reduced under conditions of timeout plus attention. Unrestrained time was gradually increased and all extra attention, i.e., more scheduled attention than provided other residents, was gradually withdrawn. When the resident was unrestrained all day and all extra attention was withdrawn, grabs and, to a lesser extent, chokes increased. Both were again reduced to a manageable level by scheduling several brief periods of attention each day. Hence, the program resulted in quick reductions that endured when the program was largely withdrawn. The changes in aggressive responding as a function of the presence and absence of extra attention suggest the importance of extra “positive reinforcement” in programs based upon positive reinforcement procedures and dealing with retarded residents for whom positive reinforcers may be scarce.

Morphological dictates of English usage call for the unvoiced allomorph /‐s/ to form the plural of singular nouns with unvoiced endings (e.g., cups). Conversely, the voiced allomorph /‐z/ is required to form the plural of nouns with voiced endings (e.g., tree). The study sought to determine the extent to which differential reinforcement could control the acquisition of plural allomorphs in two retarded subjects. In Condition 1, one subject was trained with reinforcement procedures on a list of words calling for the /‐s/ allomorph. She was then given unreinforced probe items to determine the extent of generalization to words calling for the /‐z/ allomorph. In Condition 2, the procedures were reversed and this subject was trained on a /‐z/ list and probed for generalization of /‐z/ to words calling for /‐s/. A second subject was exposed to the same conditions in the opposite order. The results for the two subjects lent unequivocal support for the hypothesis of generalized training effects. It was concluded that appropriate usage of the linguistic response class “plurals” is susceptible to generalized training effects of differential reinforcement.