Effect of hunger on starlings' preferences for food sources associated with variability or uncertainty

The information primacy hypothesis proposes that motivation to perform behaviours that reduce environmental uncertainty is continually present. It predicts that uncertain stimuli are attractive and that this attractiveness declines with increasing hunger. It also draws a distinction between the effects of stimulus uncertainty and those of stimulus variability per se (i.e. predictable variability). Two experiments investigated how hunger level affects the relative feeding preferences of starlings (Sturnus vulgaris) for two locations that always contained the same and equal amounts of food. In one experiment the locations differed in variability but not uncertainty (i.e. in one the position of a visible food item was fixed whilst in the other its position randomly varied between trials). In the second experiment the locations differed in uncertainty but not variability (i.e. in both the position of a food item varied randomly between trials but in one of them the food was not visible from the choice point and in the other it was). When satiated the birds significantly preferred to feed from (a) the variable rather than the constant location, and (b) the uncertain and variable location rather than the location that was just variable. When hungry the birds had (a) no significant preference between the constant and the variable locations, and (b) showed a shift in preference away from the uncertain location. In both experiments hunger increased the incidence of side preferences. These findings are considered in relation to both predictions derived from the information primacy hypothesis, and findings from risk-sensitive foraging experiments.