No abstract

Rats were required to bar press on an ascending sequence of fixed-ratio requirements in order to run in either a voluntary treadmill or a braked running wheel. In both testing situations the duration of the burst of running was controlled by the rat. As the ratio requirement increased the amount of bar pressing increased, reinforcement density decreased, and the duration of the pause following reinforcement increased. These changes in instrumental behavior influenced both the amount of running and the pattern of running. The level of running decreased with the ratio requirement but the average burst duration increased. Increases in running that resulted from deprivation were due to changes in burst duration rather than instrumental performance.

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Laboratory data with single exposures showed that palatability has a positive relationship with food intake. The question addressed in this study is whether this relationship also holds over repeated exposures in non-laboratory contexts in more natural environments. The data were collected in four field studies, lasting 4-11 days with 307 US Army men and 119 Army women, and comprised 5791 main meals and 8831 snacks in total. Acceptability was rated on the nine point hedonic scale, and intake was registered in units of 1/4, 1/2, 3/4, or 1 or more times of the provided portion size. Correlation coefficients between individual acceptability ratings and intakes varied from 0.22 to 0.62 for the main meals (nZ193-2267), and between 0.13 and 0.56 for the snacks (nZ304-2967). The likelihood of choosing a meal for the second time was positively related to the acceptability rating of the meal when it was consumed for the first time. The results reinforce the importance of liking in food choice and food intake/choice behavior. However, the magnitude of the correlation coefficients between acceptability ratings and food intake suggest that environmental factors also have an important role in determining intake and choice. q

A survey of U.S. Marines was conducted in order to investigate the effect of combat, a highly stressful situation, on eating behavior. The results indicate that Marines reduced their food intake, especially during their first combat experience. The principle reason cited for reduced consumption during combat was the lack of time to eat and prepare food. However, fear was important in accounting for reduced consumption during the marines' initial exposure to combat. The results are consistent with other laboratory and survey findings that stress leads to a reduction in food intake.