Maintenance-feeding effort affects instrumental performance

The effort required of rats to obtain food, employing standard maintenance-feeding procedures, can affect the effort subsequently expended in an instrumental-learning task. Rats received 43 food-rewarded runway trials followed by access to food (a) on the home-cage floor, or (b) from a hopper attached to the home-cage's wiremesh front wall. Hopper feeding involved the greater effort since the rats had to gnaw the food pellets through the wire mesh. Following 9 or 27 days of maintenance feeding, the rats were returned to the runway for one rewarded trial and 16 extinction trials. The hopper-fed rats ran faster than floor-fed rats on the rewarded test trial. In extinction, long-term maintenance feeding produced faster subsequent running times by the hopper-fed rats than the floor-fed rats. Short-term maintenance feeding, on the other hand, produced slower running times by the hopper-fed rats than the floor-fed rats. The results are consistent with previous findings of transfer of effort across behaviours and suggest that the effort required for reinforcement in the maintenance environment can systematically influence the effectiveness of various experimental treatments.     

Necessity, Sufficiency, and Perspective Effects in Causal Conditional Reasoning

A growing body of research indicates that in causal conditional reasoning, the conclusion that P is necessary for Q is suppressed where alternative conditions for Q are available. Similarly, the conclusion that P is sufficient for Q is suppressed where disabling conditions for P or additional requirements for Q are available. This paper describes experiments in which these factors were used to produce 'perspective effects' in causal contexts that appear identical to the perspective effects found in previous research with deontic tasks. It is therefore proposed that deontic perspective effects are themselves also attributable to the influence of pragmatic factors upon perceived necessity and sufficiency. A generalized theory based on a modification of the mental model theory of deontic reasoning is presented, which accounts for perspective effects across the two domains.