Robert H. Dufort

The Rat's Adjustment to 23-, 47-, and 71-Hour Food-Deprivation Schedules

In this experiment the adjustment of rats to three schedules of food deprivation was studied. Groups of Ss were placed on either 23-hr., 47-hr., or 71-hr. food-deprivation schedules for a period of 18 days. A fourth, non-deprived control group was also employed. The measures of adjustment used were body weight, and weight gain and food intake during the time food was available. The results showed that, as expected from previous research, Ss on the 23-hr. schedule were in the process of adjusting to the schedule at the end of 18 days. Ss on the 47-hr. and 71-hr. schedules, however, experienced severe weight loss and were not able to adjust to their schedules.

Water intake of the rat as a function of duration of water deprivation.

Water intake in a 2-hr. period was measured for groups of rats deprived of water either 0, 12, 24, 36, 48, 72, 96, 120, 144, or 168 hr. The intake function appeared to reach a maximum value at 48 hr., suggesting that intake is not a useful measure of the effects of long durations of water deprivation.

WEIGHT LOSS IN RATS CONTINUOUSLY DEPRIVED OF FOOD, WATER, AND BOTH FOOD AND WATER

Weight measurements were taken on four groups of rats treated according to a factorial design that combined presence or absence of food with presence or absence of water in the home cage. A 12-day deprivation period was followed by ad libitum recovery for 22 days. The main findings were: (1) Ss deprived of both food and water lost more weight than Ss deprived of either food only or water only, (2) weight loss for Ss deprived of food only and water only did not differ significantly, (3) the deprived groups were not significantly different in weight at the end of recovery, but they all weighed less than the non-deprived control group. The results were related to those of previous studies.

Adjustment of the Rat to 23-, 47-, and 71-Hour Water-Deprivation Schedules

This experiment examined the adjustment of rats to three different schedules of water-deprivation. Three groups of animals were placed on either 23-hr. deprivation (1 hr. of water every day), 47-hr. deprivation (1 hr. of water every second day), or 71-hr. deprivation (1 hr. of water every third day) for an 18-day period. A non-deprived control group was also employed. Body weight, as well as weight gain and water intake during the time when water was available, were recorded and treated as measures of adjustment. The results showed that rats adjust to the 23-hr. schedule in 2 to 3 days and to the 47-hr. schedule in 10 to 12 days. Animals on the 71-hr. schedule approached, but did not reach, adjustment; however, projection of the weight and intake trends for these Ss suggested that rats can adjust to this schedule in 27 to 30 days.

Acquisition of the conditioned eyelid response under different ready-signal conditions

Four groups were run in an eyelid conditioning experiment under different combinations of information given about, and instructions to blink to, a stimulus preceding each trial (ready signal). The group conditioned without a ready signal was superior to the other three groups, regardless of whether or not Ss in these groups blinked to the ready signal or were given information about it in the instructions.

The effect of a ready signal on the relationship between habit and drive variables in human eyelid conditioning

Performance curves for high- and low-drive groups in human eyelid conditioning were shown to diverge across training trials if no ready signal was employed. Use of a ready signal acted to mask this diverging trend in other groups that differed in drive level.

Resistance to extinction as a function of amount of reinforcement and reinforcement schedule

Sixty rats were run in an experimental design that factorially combined large and small amounts of reinforcement with 0, 12, 24, and 56 partial-reinforcement trials given after 28 continuous-reinforcement trials in a runway. Resistance to extinction was an increasing function of number of partial-reinforcement trials under large reinforcement; under small reinforcement, the partial-reinforcement groups did not differ in extinction. The results were discussed within the framework of frustration theory.

The rat’s adjustment to the 23-hour water-deprivation schedule under two conditions off food availability

Two groups of rats were placed on a 23-hr. water-deprivation schedule. Group F always had food available; Group NF had food available except during the daily 1-hr. water-intake period. Both groups adjusted to the schedule in 3 to 6 days; however, the weight of Group F increased after adjustment while weight of Group NF remained constant. The possibility that the groups differed in motivation level following adjustment was discussed.

Food Intake with and without Water after Different Durations of Food Deprivation

Food intake was measured in rats after 10 food-deprivation periods ranging from 0 to 168 hr. in duration. Half the Ss in each deprivation condition had water available during the food-intake period; the other half did not. Results showed greater intake after the shorter deprivation periods for Ss without water and greater intake after the longer deprivation periods for Ss with water. These findings were discussed in terms of the limitations on intake imposed by stomach capacity and aversiveness of dry food.