Judson S. Brown

Conditioned taste aversion produced by low doses of alcohol

A taste-aversion paradigm was utilized to demonstrate the aversiveness of intraperitoneal injections of alcohol. When injections followed immediately the ingestion of an originally preferred flavor, the extent of subsequent aversion to that flavor varied as a function of dosage (1.2 g alcohol/kg >0.8 g/kg >0.4 g/kg >0.0 g/kg). Delayed injections of 1.2 g/kg, however, did not result in significant aversion. Significant aversiveness was also demonstrated in a second experiment which utilized a “blind-injection” technique at the 1.2 g/kg dose level.

An interference-reduction theory of the effects of ethanol on conflict behavior

The classic tension-reduction theory of the effects of ethanol on approach-avoidance conflict behavior involves the assumption that the drug reduces conflict by selectively weakening fear-motivated avoidance but not approach. An alternative interpretation in which alcohol is seen as reducing the capacity of the weaker of any two competitive tendencies, whether inhibitory or excitatory, to interfere with the stronger is proposed here. Data from studies of isolated avoidance gradients and from experiments on approach-avoidance and avoidance-avoidance conflicts which support an interference-reduction rather than a tension-reduction theory are reported.

The effects of alcohol on escape learning and on regular and punished extinction in a self-punitive situation with rats

The effects of alcohol on aversively motivated locomotor behavior were examined using female rats in a short straight alleyway. A 2 by 2 by 2 factorial design included alcohol and no-alcohol conditions during escape training, and punishment or no punishment and alcohol or no alcohol during extinction of the escape response. Alcohol was found to interfere with acquisition of the escape response, to counteract the facilitatory effects of shock punishment, and to enhance performance during nonpunished extinction. The results are congruent with a traditional conditioned fear theory, amended by the notion that only partial fear responses are evoked under an inhibiting effect of alcohol. The results are also discussed in terms of state-dependency conceptions, with the addition of cue distinctiveness contributing to motivational and/or associational effects of alcohol.

A digital system for recording startle, responses in small animals

An easily constructed, isometric startle-recording system is described. The animal enclosure is attached to a plywood board-which, in ten, is mounted in a “springboard” arrangement. Movement is detected by a phonocartridge mounted beneath the chamber, and a digital record of this movement is obtained through the use of a voltage-to-frequency converter. A brief experiment in which the system was used to assess the rat’s reaction to electric footshock is also presented.

Ethanol and avoidance-avoidance conflict in the rat

The effects of ethanol on avoidance-avoidance conflict behavior in a straight runway were studied in rats with a 2 by 2 design in which shock-escape training and subsequent shock-free conflict tests were administered after the animals had orally ingested either ethanol or sugar water. Rats trained under ethanol escaped shock more slowly and, during the conflict tests, approached the shock regions less closely, started and ran more slowly, and oscillated less than sugar-water-trained controls. However, rats tested under ethanol approached the shock regions more closely, started and ran more rapidly, oscillated more, and reversed direction more than rats tested when sober. No state-dependent interactions were obtained. Some of the results were consistent with a fear-reduction hypothesis, but others supported the assumption that ethanol affected the two avoidance gradients differentially.

Variables Affecting Avoidance Conditioning in Free-Responding and Discrete-Trial Situations

The wheel-turning performance of 140 hooded rats was studied both in a free-responding and in a discrete-trial avoidance situation. A 3 × 2 × 2 design, involving comparisons of three intertrial intervals (15, 30, and 60 sec.), two CS-UCS intervals (constant and variable), and two wheel-rotation criteria (90° and 360°), was employed in the free-responding condition. Differential avoidance was found to be a positive increasing function of the length of the intertrial interval, but it was not affected substantially by CS-UCS interval or by the rotation requirement. No groups performance exceeded 42% on any day. Performance with the discrete-trial technique improved significantly in the case of the 15 sec. ITI but not for the 60-sec. ITI. Problems involved in making meaningful comparisons of free-responding and discrete-trial procedures were discussed.

Startbox-goalbox confinement durations as determinants of self-punitive behavior☆

Abstract Two levels of confinement duration (5 or 60 sec) in either startbox or goalbox were factorially combined with presence or absence of shock during extinction of a runway escape response in a self-punitive paradigm under a spaced-trials procedure. All groups were equated for amount and temporal spacing of handling before and after each trial. Shocked rats were more resistant to extinction than nonshocked rats only when startbox confinement was short. When startbox confinement was long, shock facilitated extinction. Long goalbox confinement enhanced running speed for shocked rats, but only in the presence of shock. It was suggested that duration of startbox confinement affects strength of conditioned fear, with long confinement leading to its extinction.

Speed-contingent reinforcement

A description is provided of a pellet dispenser that automatically reinforces a rat on each trial with an amount of food that is directly proportional to the speed with which the rat has traversed a runway. Preliminary data indicate that Ss reinforced on such a speed-contingent basis run significantly faster and are less variable than yoked controls.

Acquisition and extinction of runway performance under escape, avoidance, and partial-avoidance procedures

The acquisition and extinction of locomotor responses of rats in a straight alley were examined for groups trained under escape, partial-avoidance, and avoidance procedures. During acquisition, one group (escape) received a 0-sec delay between being dropped into the alley and the onset of shock; two groups (partial avoidance) had 0.5- and 1-sec delays; and two groups (avoidance) had delays of 2 and 4 sec. On the final day of acquisition, the partial-avoidance rats displayed higher running speeds than either the escape- or avoidance-trained animals. The 4-sec avoidance group was consistently slower than all other groups. Speeds for all groups decreased during extinction, with rate of decline showing some relation to terminal acquisition level. Relative group performance levels proved to be consistent with a simple arithmetic model based on the assumption that changes in running speeds affect the aversiveness of the situation by altering US duration, CS duration, and effective US length.