The double-alternative, double-start experimental apparatus: A new procedure for measuring preference

A new experimental chamber is described that permits rats to demonstrate behavioral preference for one of two conditions by running towards a goal chamber by one of two routes that are correlated with the different conditions. In a preliminary study, rats chose a route correlated with relatively lower shock, demonstrating the sensitivity of the apparatus. We also report evidence using this device that, of 10 rats tested, all preferred unsignaled rather than signaled, inescapable, unavoidable shock.     

Automation of mazes and shuttleboxes

Automation of the movement of doors in mazes and shuttleboxes may be readily achieved by a simple modification to apparatus commonly found in laboratory settings. Using a commercial timer module fitted with a “take-up” spool, a simple pulley may be arranged to lift and lower doors to permit and/or restrict access to certain areas of mazes and shuttleboxes, obviating experimenter handling.     

Color preference in pigeons: stimulus intensity and reinforcement contingency effects in the avoidance of blue stimuli.

In a procedure intended to determine color preference in pigeons (which partially replicated Catania, Owens, & von Lossberg, 1983), two keys were illuminated by different colors drawn from a set of amber, red, green, or blue stimuli; this was followed by the presentation of grain when either of the two colors was pecked. The grain was illuminated alternately across trials with the colors presented on the keys. In Experiment 1 the intensity of the color stimuli used was not equalized, whereas in Experiment 2 the intensity of the colors was equalized. The low preference for blue found in Experiment 1, as measured by differential key pecking, was not found in Experiment 2. The discriminability of the intensity-equalized colors was confirmed in Experiment 2a, in which equal-intensity color discrimination problems were presented. In Experiment 3, as in Catania et al. (1983), a response-independent reinforcement schedule was used, but with intensity-equalized colors. In contrast to Experiment 2, very low preference for blue was found here and in Experiment 4, which used a within-subject procedure. These findings suggest that pigeon color preference may be a function of intensity, but all controlling variables have not as yet been identified.     

Paradoxical preference for more frequently occurring negative stimuli and for less frequently occurring positive stimuli as a function of amount of training in simultaneous discrimination learning

Development of a preference for more frequently occurring negative stimuli was found in a within-subject design. In this experiment, pigeons learned two simultaneous problems with an unequal number of training trials. At various stages in training, for example, the more-trained negative stimulus was paired with the less-trained negative stimulus for a single preference trial. These probe trials pointed to a swing in stimulus function in negative stimuli which also occurred at an earlier stage in positive (reward-correlated) stimuli. The paradoxical preference for less-trained positive over more-trained positive stimuli was found in this study, confirming the earlier reported phenomenon. The paradoxical preference for more-trained negative stimuli was discussed in terms of a frustration analysis. A symmetrical, albeit positive, emotional factor was discussed with regard to the paradoxical findings with positive probe trials.     

Memory of conditioned food aversion follows a U-shape function in rats

Rats drinking saccharin solution for the first time were poisoned by injection of lithium chloride and then offered saccharin solution 90 min, 1, 2, 3, 7, 10 or 14 days later. The memory function was U-shaped with 90-min and 14-day groups retaining the most aversion to saccharin. Intervention with an anticholinesterase (physostigmine) failed to produce a disruption or enhancement of memory, as might have been expected from theories that the laying down of memories depends on modification of cholinergic synapses.