Initial Hunger Research Articles

Gender, dietary restraint, and smoking's influence on hunger and the reinforcing value of food

Smoking may enhance satiety following meal consumption, thereby reducing subsequent eating (i.e., between-meal snacks), especially in women high in dietary restraint. Female smokers ( n = 20, 10 high and 10 low restraint) and male smokers ( n = 10) participated in two sessions, involving overnight abstinence from food and smoking (smoking abstinence day) or from food only (smoking day), in a within-subjects design. The reinforcing value of food was determined by the number of responses made to obtain food reinforcers (100-kcal snack portions) vs. money using a concurrent schedules computer task. Subjects were given a small caloric load on each day followed by access to food vs. money. On the smoking day, subjects were allowed to smoke every 30 min during the session as well as ad lib before the session. Self-reported hunger was also assessed upon arrival (after fasting) and following the caloric load during each session. Results indicated no effect of smoking on initial hunger rating, after fasting, but hunger ratings following the caloric load declined significantly more during smoking vs. abstinence days for all subjects, consistent with an enhancement of postmeal satiety due to smoking. There was no overall main effect of smoking on food-reinforced responding. However, responding for food was significantly less during the smoking vs. abstinence days for high-restraint females only and not for low-restraint females or for males. These findings indicate that smoking's acute influence on reducing food intake does not reflect a broad gender difference but may be specific to dietary restraint.

Influence of hunger level and food availability on the spatial distribution of Atlantic salmon, Salmo salar L., in sea cages

Abstract. The spatial distribution of Atlantic salmon, Salmo salar L., in sea cages was observed by echo integration, which measured fish density at seven in depth intervals. At start of feeding the fish swam towards the surface and into the centre of the cage with a subsequent movement downwards and towards the periphery as hunger was reduced. These changes were more rapid at high than at low feeding intensities. The downward migration during feeding was primarily observed as a reduction in fish density in the 0–1 m depth layer and an increase in the 2–3 m depth layer. For a given feeding intensity, the change in fish density in these depth layers was largely explained by time from the start of feeding and initial hunger level, measured as food intake to satiation. The feeding regime also influenced vertical distribution outside feeding periods. Fish that were fed at low intensity swam generally closer to the surface, and this tendency was even stronger when a restricted food ration kept hunger level constantly high. While fish density peaked at a single depth interval at full ration, a bimodal vertical distribution was observed at restricted ration, suggesting that different subgroups of fish had different feeding motivations. The results suggest that the vertical distribution of salmon in sea cages is based on a trade-off between attraction to food and avoidance of the surface. This tendency has been exploited in a new method of demand feeding in commercial farming of Atlantic salmon.

Is the effect of a social model on eating attenuated by hunger?

Two experiments were conducted to assess the effect of social influence pressures on eating in indivudals differing in initial hunger; we assumed that conformity to a model would decline as hunger increased. In the first experiment, subjects' eating conformed closely to the model's eating, with subjects eating very little when the model ate very little, even after 24 h of food deprivation. In a second experiment, the conformity effect again dominated the results, even after lengthy deprivation. We discuss the implications and limitations of this powerful modelling effect on eating.

The influence of hunger on feeding behaviour and on the acquisition of learned foraging skills by the fifteen-spined stickleback, Spinachia spinachia L.

Increased hunger and associated feeding motivation increased the foraging efficiency of sticklebacks already experienced with Gammarus or Artemia as prey. Behavioural components additional to the basic foraging sequence were performed less frequently and reaction distance and speed of attack increased as handling time decreased. Foraging efficiency also increased as naive fish gained experience with prey, but the rate of learning was modified by the forager's initial hunger level. Fish deprived of food for 24 h acquired attack and handling skills faster and more thoroughly than those fed to 50 and 95% satiation. Learning increased the profitability of both Gammarus and Artemia. Whether a less profitable prey type can become more profitable than another will, however, depend critically on the prey-specific intrinsic rates of increase and decrease of handling time associated with the independent effects of learning and satiation, and on the forager's initial level of hunger.