[Study of impulsivity in rats under conditions of choice between food reinforcements of different values].

Rat behavior was studied under conditions "with the right to choose the values of reinforcements depending on the time delay of its receipt". Rats were placed in a chamber equipped with two retractable pedals, pressing one of which provided a small portion of food (1 pellet), and pressing the second pedal was followed by the delivery of more valuable food (4 pellets), but delayed reinforcement. Rats preferring small reinforcement without the delay were considered as "impulsive" and rats choosing more valuable delayed reinforcement were considered as "self-controlling". Influence of the delay duration and change in the level of motivation on the pedal pressing was studied in both groups of rats. Preference in the selection of the pedal, latency of pressing the pedal and the number of omitted reactions were estimated. It was found that "impulsive" animals more rapidly pressed the pedal and less frequently omitted trials than "self-controlling" rats. After the increase in the delay duration up to 7 seconds, rats stopped choosing the pedal with the delayed reinforcement. Increased food motivation shifted the behavior of rats to "self-control", whereas rats after feeding preferred less valuable immediate reinforcement.