An experiment was carried out to investigate whether nicotine ingestion (via cigarette smoking) interacted with alcohol (vodka and tonic) in its effect on state-dependent learning (SDL) in humans. On Day 1 of the 2-day experiment 24 subjects were required to learn a simple route map previously found to be SDL sensitive with alcohol. All subjects ingested 0.66 g alcohol/kg body wt. and smoked two medium tar cigarettes (average nicotine content 1.4 mg). Twenty-four hours later, subjects attempted recall under one of the following drug states; (i) alcohol and nicotine (A + N); (ii) alcohol and smoking placebo (A + O); (iii) Nicotine and placebo drink (O + N); and (iv) no drugs (O + O). Highest recall scores were observed in the A + N subjects, with O + N and O + O subjects recalling the least. A + O subjects had intermediate recall performance. Thus the combination did produce a clear SDL effect, with alcohol possibly contributing the major influence.
Rats were placed in an experimental chamber for 30 min. on two successive days. On day 1 they experienced either continuous steady light or continuous flickering light. On day 2 the box was dark, with either steady light or flicker contingent upon a bar press. A greater light reinforcement effect was found when the illumination contingent upon a response was different from the pre‐test illumination.
The effects of temporal and lateral uncertainty were separately shown to produce decrements in the detectability of a tonal signal in noise. Rating procedures were used, together with left/right recognition responses where appropriate. When both dimensions of uncertainty were present simultaneously, the interaction was found to be complex. Observed false-alarm rates provided a reliable index of the possible detection strategies involved in these tasks.
The effects of continuous and discontinuous periods of apparatus familiarization on light reinforcement in rats were examined. A previous finding that the light reinforcement effect is greater with longer pretest periods in the dark box was confirmed by comparing 270 min and 30 min periods in the box prior to testing 24 h later. A discontinuous period of 9 daily 30 min sessions, however, produced a bigger effect than the 270 min continuous period. It was concluded that the degree of familiarization with the apparatus is a more important factor than length of time per se in the dark in determining the effectiveness of light as a reinforcer.
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