The present series of experiments tried to provide information about the associative value of the CS in backward conditioning and further our knowledge of approach behavior (APPR$\sp-$) towards a CS which signals absence of an aversive US. In all experiments, the US was a foot-shock (.5 mA, 2 sec) and the CS was a platform accessible for short time periods each trial. Time spent on the platform was used as a measure of APPR$\sp-$ behavior. Experiment 1 compared the effects of backward, differential, and explicitly unpaired procedures with a random procedure on the development of APPR$\sp-$ behavior. The results showed rapid acquisition of APPR$\sp-$ behavior in each of the experimental groups in comparison with the random group. In a subsequent retardation-of-acquisition test (forward pairings), all experimental groups showed gradual suppression of APPR$\sp-$ behavior, suggesting conditioned inhibition to the platform-CS in each of the experimental groups. Experiment 2 studied the effect of the number of backward pairings on APPR$\sp-$. The results showed that five or ten daily pairings were sufficient for the rapid acquisition of APPR$\sp-$ behavior, while one daily pairing produced WDR$\sp+$ behavior (a behavioral tendency opposite to APPR$\sp-$ behavior). In a subsequent retardation-of-acquisition test, the experimental group exposed to five daily pairings showed rapid suppression of APPR$\sp-$ behavior. These results were interpreted in terms of possible differential level of conditioned inhibition to the CS produced by differential number of US-CS pairings. Experiment 3 studied the effect of ITI lengths on the development of APPR$\sp-$ behavior in backward conditioning. A strong APPR$\sp-$ behavior was observed when the ITI range was long (2 to 4 min), but not when ITI range was sometimes short (10 sec) and sometimes long (5 min). These results showed that the CS must reliably signal a relatively long period without shock for the development of APPR$\sp-$ behavior. In Experiment 4, conditioned inhibition to the CS in backward pairings was evaluated independently of APPR$\sp-$ behavior, in the context of a conditioned suppression paradigm. The results showed that US-CS pairings procedure produced less suppression of drinking than CS-US pairings, but no response acceleration in comparison with the control condition. Time spent on the platform and behavioral observations failed to provide evidence of the inhibitory properties of the CS in the backward conditioning group possibly due to extinction during testing sessions. In conclusion, it seems that under specific conditions, the CS in backward conditioning acquires inhibitory associative value and a conditioned inhibition mechanism would be partly responsible for APPR$\sp-$ behavior. However, temporal contiguity seems to be an essential element to APPR$\sp-$ behavior. At a theoretical level, a modified stimulus substitution model could be considered as an alternative to a contingency model explaining APPR$\sp-$.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/5751 |
| Date | January 1989 |
| Creators | Bernard, Diane. |
| Contributors | Leclerc, R., |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Detected Language | English |
| Type | Thesis |
| Format | 272 p. |
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