Abstract: In three experiments on the social induction of food preferences in rats, I found: (a) that eight 30-min exposures of a naive “observer” rat to a “demonstrator” rat fed one of two approximately equipalatable diets produced observer preference for the diet fed to its demonstrator that lasted for more than a month, (b) that simple exposure of naive subjects to a diet itself, rather than to a rat that had eaten a diet, was not sufficient to enhance preference for that diet, and (c) that lasting preference for an unpalatable, piquant diet could also be established by exposing naive rats to demonstrators that had eaten the piquant diet, but not by simply exposure to the piquant diet itself. These findings are consistent with the hypothesis proposed by both Birch and Rozin that social-affective contexts are important in establishing stable, learned preferences for foods.

Abstract: A computer-controlled push-door system was designed and tested as a method for measuring motivation. Eleven domestic hens were trained to use the push-door to gain access to food. They were deprived of food for 12 h or 43 h on 12 occasions and the push-door was used to measure the amount of “work” (measured as force × time) that they performed to gain access to a food reward. When deprived of food for 12 h the hens took significantly longer (P<0.01) to reach the required threshold of work, than when deprived for 43 h. This difference arose from the amount of time that the hens spent not pushing at the door. The problems encountered with this system and such an approach to measuring motivation are discussed.

Abstract: Changes in the secondary structure of some dozen different proteins upon lyophilization of their aqueous solutions have been investigated by means of Fourier-transform infrared spectroscopy in the amide III band region. Dehydration markedly (but reversibly) alters the secondary structure of all the proteins studied, as revealed by both the quantitative analysis of the second derivative spectra and the Gaussian curve fitting of the original infrared spectra. Lyophilization substantially increases the beta-sheet content and lowers the alpha-helix content of all proteins. In all but one case, proteins become more ordered upon lyophilization.

Abstract: Group living commonly helps organisms face challenging environmental conditions. Although a known phenomenon in humans, recent findings suggest that a benefit of group living in animals generally might be increased innovative problem-solving efficiency. This benefit has never been demonstrated in a natural context, however, and the mechanisms underlying improved efficiency are largely unknown. We examined the problem-solving performance of great and blue tits at automated devices and found that efficiency increased with flock size. This relationship held when restricting the analysis to naive individuals, demonstrating that larger groups increased innovation efficiency. In addition to this effect of naive flock size, the presence of at least one experienced bird increased the frequency of solving, and larger flocks were more likely to contain experienced birds. These findings provide empirical evidence for the “pool of competence” hypothesis in nonhuman animals. The probability of success also differed consistently between individuals, a necessary condition for the pool of competence hypothesis. Solvers had a higher probability of success when foraging with a larger number of companions and when using devices located near rather than further from protective tree cover, suggesting a role for reduced predation risk on problem-solving efficiency. In contrast to traditional group living theory, individuals joining larger flocks benefited from a higher seed intake, suggesting that group living facilitated exploitation of a novel food source through improved problem-solving efficiency. Together our results suggest that both ecological and social factors, through reduced predation risk and increased pool of competence, mediate innovation in natural populations.

Abstract: Group living offers well-known benefits to animals, such as better predator avoidance and increased foraging success. An important additional, but so far neglected, advantage is that groups may cope more effectively with unfamiliar situations through faster innovations of new solutions by some group members. We tested this hypothesis experimentally by presenting a new foraging task of opening a familiar feeder in an unfamiliar way to house sparrows in small and large groups (2 versus 6 birds). Group size had strong effects on problem solving: sparrows performed 4 times more and 11 times faster openings in large than in small groups, and all members of large groups profited by getting food sooner (7 times on average). Independently from group size, urban groups were more successful than rural groups. The disproportionately higher success in large groups was not a mere consequence of higher number of attempts, but was also related to a higher effectiveness of problem solving (3 times higher proportion of successful birds). The analyses of the birds' behavior suggest that the latter was not explained by either reduced investment in antipredator vigilance or reduced neophobia in large groups. Instead, larger groups may contain more diverse individuals with different skills and experiences, which may increase the chance of solving the task by some group members. Increased success in problem solving may promote group living in animals and may help them to adapt quickly to new situations in rapidly-changing environments.