Choosing between fixed time and variable time shock

Two experiments are reported dealing with choice of fixed or variable time shock schedules with and without signals. Response independent shock was presented on either a fixed-time or a variable-time schedule and subjects could change from one condition to the other for short periods after which the initial condition was automatically reinstated. In the first experiment shocks for both schedules were either unsignalled (6 subjects) or signalled (3 subjects) and all subjects changed from a schedule of variable-time shock to a fixed-time one. Subjects that were given the opportunity to change in the reverse direction did not do so. Opposite findings were obtained in the second experiment (7 subjects) comparing unsignalled fixed-time shock with signalled variable-time shock. Six of the seven subjects changed from the fixed-time schedule to the signalled variable-time one but not the reverse. The data were considered consistent with an analysis of choice based on the reinforcing value of discriminable shock-free periods.     

Choice of higher density signalled shock over lower density unsignalled shock

Unsignalled, inescapable shocks were presented to four albino rats in Experiment 1. By pressing a lever subjects could change the condition to signalled shock for 3-min periods after which unsignalled shock was automatically reinstated. All subjects changed from unsignalled to signalled shock when shock density was the same or when the density of signalled shock was two times greater than unsignalled shock. When the density of signalled shock was four times that of unsignalled shock, three subjects changed to the higher density schedule. One subject changed to a density of signalled shock eight times that of unsignalled shock. The second study showed that the two shock schedules most similar in Experiment 1 were discriminably different because subjects chose lower over higher shock densities when both densities were unsignalled. An analysis stressing safe (signal absent) and unsafe (signal present) periods was discussed.     

Paraconsistent Metatheory: New Proofs with Old Tools

Journal of Philosophical Logic - This paper is a step toward showing what is achievable using non-classical metatheory—particularly, a substructural paraconsistent framework. What standard...     

The relative aversiveness of signalled vs unsignalled avoidance

Subjects avoided shock by pressing on one lever under an unsignalled condition, but by pressing a separate lever they changed the condition to signalled avoidance for 1-min periods. Signalled avoidance periods were identified by a correlated stimulus. All eight subjects responded to change the unsignalled schedule to a signalled one. Once contact with signalled avoidance was made, subjects continued responding to remain in that condition. Other tests showed that changeover responding was greater when the correlated stimulus was presented without the signal than when the signal was presented without the correlated stimulus. An analysis based upon shock and shock-free periods is presented.     

On Sahlqvist Formulas in Relevant Logic

This paper defines a Sahlqvist fragment for relevant logic and establishes that each class of frames in the Routley-Meyer semantics which is definable by a Sahlqvist formula is also elementary, that is, it coincides with the class of structures satisfying a given first order property calculable by a Sahlqvist-van Benthem algorithm. Furthermore, we show that some classes of Routley-Meyer frames definable by a relevant formula are not elementary.     

Choosing schedules of signaled appetitive events over schedules of unsignaled ones

Two experiments were completed allowing albino rats to choose between signaled and unsignaled reward conditions. These experiments examined the effects on preference of (1) response dependent versus response-independent reward and, (2) food pellets versus chocolate milk as the reward. All subjects preferred the signaled condition over the unsignaled condition, whether exposed to response-dependent, or to response-independent delivery of rewards. Preference was controlled most effectively by presenting both the signal itself and the correlated stimulus identifying the signaled condition. The signal presented alone (Extinction 3) controlled preference more effectively than did the stimulus correlated with the signaled condition (Extinction 2). The second experiment showed that the quality of the reinforcer (pellets and chocolate milk) did not affect preference for signaled reward since all subjects preferred the signaled condition at levels comparable to those observed in Experiment 1, with food pellets. These results, along with others, argue against species differences, response-dependency, and reinforcer quality as variables affecting the direction of preference.     

Preference for signaled over unsignaled shock schedules: Ruling out asymmetry and response fixation as factors

Experiment 1 tested whether a “symmetrical” choice procedure yields results different from those previously reported using the “unidirectional” standard changeover procedure (e.g., Badia & Culbertson, 1972). Subjects could change at any time from unsignaled to signaled shock by pressing a lever and from signaled to unsignaled shock by pressing a second lever. Results were identical to those of the standard procedure and showed that the standard procedure is fully adequate. Experiment 2 tested whether choice of high density signaled shock over low-density unsignaled shock (Badia, Coker, & Harsh, 1973) resulted from initial training with equal-density schedules. Subjects were trained and tested with signaled shock twice as dense as unsignaled shock. Three of four subjects strongly preferred the signaled condition, thus ruling out carry-over and “response fixation” as alternative explanations.