The effects of a dexamphetamine-amylobarbitone sodium mixture on the reward value of different sensory changes

The effect of a dexamphetamine-amylobarbitone mixture (1;6.5 by weight) on a sensory-contingent bar pressing (SCBP) for different sensory changes was investigated. The aim was to examine the role of (a) reward value of contingent change per se (non drug) and (b) stimulus properties in enhanced SCBP under the drug mixture. The sensory reinforcers used were light Onset, light Offset, and sound offset combined with the light changes contemporaneously. In the first two phases the sensory stimuli were given as continuous reinforecement and in the third phase on an FR2 schedule. The results from the first two phases were consistent with the notion that the drug mixture responding under the drug was enhanced was not significantly related to the kind of sensory change. Instead, responding under the mixture was enhanced in proportion to the level of non drug responding, especially in Phase 1. However, in Phase 3, SCBP was enhanced proportionately more, to a significant extent, in those treatments receiving the combined light and sound change. It was concluded that properties of the sensory stimuli other than their reward value per se (non drug) may also be related to the extent of SCBP enhancement under the drug mixture. In particular, properties of the sound offset reinforcer appear to make it more amenable to enhancement under the drug than the two light reinforcers.