Effect of procurement cost on the drinking of a saccharin-sucrose solution by non-deprived rats

Behavioral and Neurochemical Mechanisms of the Action of Mild Stress in the Enhancement of Feeding

Rats were trained to respond under a cyclic-ratio schedule of reinforcement composed of an ascending, followed by a descending, sequence of ratio values. Subjects were trained while exposed to 70 dB white noise, then tested while exposed to 70 or 90 dB white noise. Exposure to 90 dB white noise elevated the response function (p<.02). Naloxone was then administered intraperitoneally at 0.3. 1.0. and 3.0 mg/kg under 70 dB and 90 dB white noise. Naloxone administration (1.0 and 3.0 mg/kg) significantly depressed the response function obtained under 90 dB white noise (ps<.01) but did not affect the function obtained under 70 dB white noise. These findings suggest that mild stress increases food intake through a mechanism affecting palatability enhanced by the release of endogenous opioids.

Efficiency and persistence of licking in rats

Thirsty rats tested in 60-min sessions licked an empty spout for access to a water spout. We raised the behavioral price of the water lick by requiring more licks at the empty spout per lick at the water spout. At relatively high prices the rats made relatively few water licks but licked more efficiently, getting more water per lick. Controls showed that the rise in efficiency with price was not attributable to two variables previously confounded with price: the total number of water licks, and the temporal pattern of access. At a higher price the rats also licked more persistently, making more extra water licks before the shutter could occlude the spout. However, yoked controls showed that the greater persistence resulted not from price, but from the relatively stringent pattern of access that accompanied the higher price. Extra water licks diminished as the session progressed, apparently from satiety, not fatigue. The results have implications for behavioral ecology, behavioral economics, motivation, and the methodology of reward.

The effect of auditory stimulation on the consumption of soft drinks

Three groups of five male and five female students were exposed to different levels of auditory stimulation (no music or music played at 70 dB or 90dB) under naturalistic conditions and were permitted to avail themselves freely of a supply of soft drinks. Increasing auditory stimulation produced an increase in total consumption. Reported prior frequencies of soft drink consumption and of exposure to loud music had no bearing on the result of the experimental manipulation, suggesting that the effect was not due to previous history.

Responses of fowls to an operant feeding procedure and its potential use for reducing randomness in meal occurrence

Adult laying hens were tested with increasing and decreasing procurement costs (pecks at a disc) which allowed access to food for unlimited periods. This was done to observe changes in feeding behaviour, to see whether apparent randomness in meal occurrence can be reduced, and, if so, to identify an appropriate fixed ratio (FR) for incorporating in investigations of physiological correlates of hunger and satiety. Daily food intake stayed the same at all but the highest (160 pecks) FR. FR sizes were related negatively to total time feeding and meal frequency, and positively to intermeal interval length, meal size and rate of eating within meals. They were also related positively to meal length, but only weakly so. Frequency distributions of meal and interval lengths, and postprandial correlation coefficients, indicated that randomness in feeding did decline at higher FRs, and FR20 seems the most appropriate schedule for potential use in physiological experiments.

Effects of rate and distance of procurement wheel-running on saccharin-and-sucrose solution drinking by non-deprived rats

Four non-deprived rats received daily sessions of 20 min access to a saccharin-and-sucrose solution following various prior activities, in an attempt to disentangle the normally confounded roles of time spent, amount and rate of procurement responding in causing an increase in consumption once access is gained. After the normal rate of running (approx 35 m/min) was established, six conditions were run in random order, involving waiting zero and 2.5 min in an immobilised running-wheel, and running, with the wheel rotated by a motor, in four conditions formed by combining two speeds (12 and 30 m/min) with two distances (12 and 30 m), prior to access to the solution. Drinking increased with the speed of prior running, and to a lesser extent with the distance run, but was not related systematically to the time spent running. It is suggested that information from the animal's own behavior in gaining access to a commodity, particularly the rate of energy expenditure, may influence its utilisation of the commodity by affecting the rate of subsequent consummatory responding.