Carlos A. Bruner

The activity of rats in a swimming situation as a function of water temperature.

Previous research has shown that time before drowning in rats decreases gradually as stress is increased by varying water temperature in the swimming situation. In the present research, the activity of swimming rats appeared to be a U function of varying water temperature, lending support to the notion that activity is a behavioral measure that estimates the rats chances of survival in the water. This conclusion was further supported by the covariation of activity with a different behavioral measure of survival. In addition, activity during sessions decreased gradually, suggesting that a lowered activity is an adaptive response in the rat. Activity, thus, appears to be negatively correlated to the rats survival chances under colder (14-23 degrees) and warmer (23-47 degrees) temperatures; i.e., in a more stressful situation, including extreme fear. It may be, therefore, that a decrease in activity obtained in present laboratory models (i.e., immobility) is more relevant to the extinction of fear than despair, as reported by other researchers.

OBSERVING RESPONSES AND SERIAL STIMULI: SEARCHING FOR THE REINFORCING PROPERTIES OF THE S−

The control exerted by a stimulus associated with an extinction component (S-) on observing responses was determined as a function of its temporal relation with the onset of the reinforcement component. Lever pressing by rats was reinforced on a mixed random-interval extinction schedule. Each press on a second lever produced stimuli associated with the component of the schedule in effect. In Experiment 1 a response-dependent clock procedure that incorporated different stimuli associated with an extinction component of a variable duration was used. When a single S- was presented throughout the extinction component, the rate of observing remained relatively constant across this component. In the response-dependent clock procedure, observing responses increased from the beginning to the end of the extinction component. This result was replicated in Experiment 2, using a similar clock procedure but keeping the number of stimuli per extinction component constant. We conclude that the S- can function as a conditioned reinforcer, a neutral stimulus or as an aversive stimulus, depending on its temporal location within the extinction component.

A cross-cultural study: a comparison of German, Spanish and Ecuadorian alcoholics using the Munich Alcoholism Test (MALT).

Having validated the Munich Alcoholism Test in three different countries (Germany, Spain, and Ecuador), it was determined that five of the 31 items of the test were very consistent in revealing similarities among these three alcoholic populations.

RESPONSE ACQUISITION WITH INTERMITTENT IMMEDIATE AND DELAYED CONDITIONED REINFORCEMENT

The acquisition of lever pressing by rats was studied under intermittent immediate and delayed conditioned reinforcement. Rats were exposed to two schedules operating concomitantly. One was a random-time schedule that delivered reinforcers on average of once per min. Each such reinforcer was paired with a 1-s illumination of a cue light located above the lever. The other was a tandem random-interval (RI) t₁ - s fixed-time (FT) t₂ - s schedule that controlled the rate and the delay of the illumination of the cue-light after a given lever press. For the RI, t₁ was 7.5, 15 or 30 s. For the FT, t₂ was 0, 1, 2, 4, 8, 16 or 32 s. Three rats each were exposed to each combination of RI and FT values for 40 sessions. Response rates decreased with longer response-conditioned reinforcer (S(r)) delays under the three different overall rates of S(r). At most response-S(r) delays, absolute response rates were higher with RI 15 s than with RI 30 s but both were similar to those obtained with RI 7.5 s. The results were similar to those from previous research on response acquisition with delayed primary reinforcement. These findings suggest that a previously neutral stimulus that has been correlated with primary reinforcement can reinforce new responses even when the conditioned reinforcer is intermittent and delayed from the responses that produce it.

La tasa de respuesta en el eslabón apetitivo de cadenas homogéneas y heterogéneas con ratas como sujetos

Investigaciones en programas encadenados de dos componentes han encontrado que Ia tasa de respuesta durante el primer componente es mas alta cuando se requieren respuestas similares en ambos componentes. Sin embargo en dichas investigaciones se han usado solamente palomas, y ademas se ha confundido la similitud de las respuestas con su localizacion. En el presente estudio se intento replicar el hallazgo con ratas y ademas evaluar por separado el efecto de Ia similitud y la localizacion de la respuesta. Tres ratas completaron cadenas en las que se requirio presionar una palanca o jalar una cadena en uno o ambos componentes. Los dos tipos de respuesta se balancearon para producir diferentes condiciones en las cuales la respuesta era la misma o diferente y tenia que ocurrir en el mismo o en diferente lugar. Cuatro de seis condiciones en las cuales las respuestas fueron similares y su localizacion fue la misma, produjeron tasas de respuesta, en el primer componente, mas altas que cualquier otra condicion comparable. Estos hallazgos muestran quo los efectos de las cadenas homogeneas son generales entre palomas y ratas y que la distancia entre operandos contribuye al efecto en cuestion.