Indexador

Resumo não informado pela fonte indexada.

In order to assess possible confounding of discriminative stimulus effects with those produced by the reinforcing stimulus, three groups of four rats each were trained for 45 hr on a variable‐interval 1‐min reinforcement program. Two groups were run on a multiple variable‐interval extinction schedule in which the reinforcement stimulus (SD) and the nonreinforcement stimulus (SΔ) were two intensities of a 4‐kHz (cps) tone separated by 40 or 10 db. The third group was run on a mixed schedule with a single intensity constantly present. The mixed‐schedule animals showed no discrimination of the reinforcement program. Under the multiple schedule, the highest SΔ rates were obtained after SD intervals, regardless of the reinforcement availability in the SD interval. These local rate variations in SΔ were small in proportion to those produced by the SD versus SΔ intensities.

Aversive stimuli are known to produce the behaviors of both escape and attack. The interaction between these two basic reactions was studied with rats and monkeys using many shock‐escape and shock‐avoidance procedures. All procedures produced attack if a target was present, the attacks occurring shortly after shock delivery. The number of attacks during escape or avoidance was a direct function of the number and duration of shocks received. Consequently, any aspect of the procedure that produced many shocks also produced many attacks such as initial acquisition, extinction, or an increase of the response requirement for escape. The escape tendency acquired prepotency over the tendency to attack since successful escape eliminated attack behavior. The attack tendency retarded escape behavior only during acquisition when the preoccupation with attack precluded the opportunity to learn the escape response. This mutual interference of escape and attack was eliminated when the attack and avoidance tendencies were combined by using biting attack as the shock‐avoidance response. The result was unusually rapid conditioning of the biting‐attack response. These interactions indicate that both the attack and escape tendency should be considered whenever aversive stimulation is delivered.

Pigeons were exposed to a cyclic schedule in which each cycle was composed of twelve 1‐min fixed intervals followed by four 3‐min fixed intervals; four such cycles comprised an experimental session. The pigeons responded at a much higher average rate during the 3‐min intervals than during the 1‐min intervals. Other effects were a depression of responding during the first short interval of each cycle and a shortening of postreinforcement pause during the second short interval. The main effect is attributable to a relatively fixed pattern of responding after reinforcement; this pattern consisted in a pause of approximately constant duration followed by responding at an approximately constant rate until the next reinforcement, resulting in much higher average response rates during the longer interreinforcement intervals. The other effects seem attributable to relatively slight differences between the pattern of responding characteristic of later long intervals and the pattern during later short intervals of each cycle. A major implication is that the pigeon is largely insensitive to the sequential properties of many interval‐reinforcement schedules. A description of interval‐schedule “frustration” phenomena in terms of the inhibitory effects of reinforcement is discussed in relation to these results.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.

Resumo não informado pela fonte indexada.