Reinforcement In Rats Research Articles

Interaction between Effort and Partial Reinforcement in Free Operant Response of Rats and Fish

Rats and fish were trained to give a free operant response under partial versus consistent reinforcement and high versus low effort. Resistance to extinction was then measured in terms of number of responses to criterion (R), time to criterion (T), and rate to criterion (R/T). Effort failed to affect any of these measures in either species. In rats partial reinforcement produced greater resistance to extinction than consistent reinforcement on R and T, but not on R/T, whereas partially reinforced fish failed to differ from those consistently reinforced on R and T bur exceeded the consistently reinforced fish on R/T. The R and T measures were correlated in both groups of fish but only in the consistently reinforced rats. Partially reinforced fish were less variable than consistently reinforced fish on the T measure. It is suggested that the principal effect of partial reinforcement in rats is on mean time to extinction, but the effect in fish is on variability of time to extinction.

Differential conditioning based on concentration of sucrose reinforcement in rats on a VI schedule

Seven rats received extended bar-pressing training on a VI schedule with 8% and 32% sucrose reinforcement. During days in which 32% and 8% alternated in 10-min. stimulus-correlated periods, response rate and speed of the first response were greater for 32% solution. The possible contribution to such results of reinforcement contrast is discussed.

Stimulus-Change versus Preference for Light

The classical procedure for demonstrating the reinforcing properties of stimulus-change for rats confounds the response-contingent change with the production of dim illumination. This experiment unconfounded the two by providing a response-contingent visual change without a change in the ambient illumination. This “pure” visual change was not reinforcing, whereas a response-contingent change from darkness to dim illumination—the classical procedure—was unambiguously reinforcing. Thus much research purporting to demonstrate reinforcement in rats by “visual change” can be reinterpreted as demonstrating that dim illumination is preferred over darkness.

CHANGE IN MOTOR ACTIVITY AS REINFORCEMENT IN RATS, CHICKS, AND FISH.

CHANGE IN MOTOR ACTIVITY AS REINFORCEMENT IN RATS, CHICKS, AND FISH.

Hypothalamic substrates of reward.

Hypothalamic substrates of reward.

Some observations on the adventitious reinforcement of drinking under food reinforcement.

The development of strong postreinforcement drinking behavior under variable-interval food reinforcement in rats was found to be influenced by the proportion of short intervals in the VI and the proximity of the water tube to the lever.

Secondary reinforcement in rats as a function of information value and reliability of the stimulus.

Secondary reinforcement in rats as a function of information value and reliability of the stimulus.

Duration of Weak Light Reinforcement

Studies of weak-light onset reinforcement in rats have used lights of fixed durations ranging from M to 5 sec., or have left the light on as long as the lever was held down. The present experiment tested the effect of the light's duration upon conditioned lever pressing. The apparatus was a Skinner box made from a rat living cage and containing a 1-in.-wide lever. A 25-w frosted lamp bulb was mounted outside the cage, 5 in. above the bar. A resistor reduced the lamp voltage to 95 v. S was first left in the darkened box for a 10-min. habituation period. Then, 10 light-onset reinforcements were given and were followed immediately by a 20-min. extinction period in darkness.' For one group of 16 Ss (female yearold abino rats), the light stayed on for y3 sec., regardless of the duration of the press. Other groups of 16 received lights lasting 1, 3, and 9 sec. Effect of the conditioning was measured by the number of presses during extinction. For the Y3-, I-, 3-, and 9-sec. groups, the mean frequencies were 11.4, 14.2, 15.8, and 13.1 presses, respectively. Simple analysis of variance did not reveal a duration effect approaching significance. In fact, the withingroups mean square exceeded that between groups, although not by a significant a m o ~ n t . ~ These results suggest that reinforcement results from the change from darkness to light, rather than from the light itself. Thus they lend some support to the stimulus-change interpretation of weak-light reinforcement. Other evidence, however, such as the usual failure to obtain reinforcement by light offset (e.g., Robinson, 1959) seems inconsistent with the hypothesis that all stimulus changes are reinforcing to rats.

Role of Adrenalin in Recovery of Inhibited Conditioned Reactions

SummaryConditioned reactions which had been inhibited by lack of reinforcement in rats may be restored by insulin coma in normal as well as in adrenodemedulMted rats. Apparently a secretion of adrenalin which is observed under conditions of insulin coma and electroshock does not play an integral part in the mechanism of the restoration of inhibited conditioned reactions. This interpretation is supported by the fact that the injection of adrenalin remains ineffective in the normal animals as far as restoration of inhibited conditioned reactions is concerned, whereas insulin coma and electroshock restore these reactions. It is inferred from these experiments that the restitution of inhibited conditioned reactions is linked up with a hypothalamic-cortical discharge previously established by Murphy and Gellhorn and is not due to the liberation of adrenalin which invariably accompanies the excitation of hypothalamic centers under conditions of insulin coma and electroshock.