Roger L. Mellgren

Neophobia when feeding alone or in flocks in zebra finches, Taeniopygia guttata

Abstract Abstract. Differences in the feeding behaviour of solitary and groups of three (flocks) adult male zebra finches were investigated. Neophobia (fear and avoidance of new things) was induced by presenting subjects with novel feeders and also adorning the feeders with different novel objects. The results showed that subjects in the flock entered the feeder and began feeding sooner than the solitary birds. The birds in the flock condition also entered the feeder sooner than solitary birds when novel objects adorned the feeder, although the magnitude of the difference depended on the specific object used. Because members of the flock could not directly observe the first member feeding, a social following mechanism seems to describe best the behaviour of flock members, rather than local enhancement.

Sex differences in the acquisition of a radial maze task in the CD-1 mouse

The purpose of the present study was to investigate spatial processing performance in male and female CD-1 mice. A substantial literature supports the existence of significant sex differences in both human and rodent models of learning and memory. The nature of these differences is dependent upon the parameters of the task, species and strain of animal. In the present study, male and female CD-1 mice were trained for 3 days to perform a 4/8 spatial memory task in an eight-arm radial maze and then tested for a total of 5 days. On the final day of radial maze testing, male CD-1 mice committed marginally significantly fewer reference memory (RM) and significantly fewer working memory (WM) errors on the radial maze task than female CD-1 mice. In addition, female mice obtained significantly fewer rewards during the final two testing sessions. The present data provide the first evidence for sex differences in radial maze learning in the CD-1 mouse, a strain known for its estrogen insensitivity. Consistent with the majority of literature that supports sex differences in spatial processing in rodents, female CD-1 mice acquired significantly fewer rewards than male CD-1 mice during an eight-arm radial maze task.

Extinction of operant behavior: An analysis based on foraging considerations

In two experiments, the frequency of food reinforcement provided by variable interval (VI) schedules prior to extinction was varied. In the first experiment, two-component multiple schedules resulted in a greater number of responses in extinction in the presence of the stimulus previously associated with the richer of the two component schedules than that previously associated with the leaner schedule. In the second experiment, different groups of animals were trained on different VI schedules. Responding in extinction was analyzed into bouts of responding showing that the number of response bouts increased and the number of responses per bout decreased with decreasing frequency of reinforcement during training. These data are compatible with an analysis of operant behavior based on an analogy to processes that presumably-occur-in naturalistic foraging situations. According to this analogy, behavior associated with search for a food source (i.e., number of response bouts) and that of procurement of food from a source (i.e., responses per bout) represent aspects of behavior that are differentially strengthened by different VI schedules. Extinction serves to reveal this differential strengthening.

A cognitive emotional network model of foraging under predation risk

The cognitive emotional foraging model (CEF) is a unique application of a neural network to dynamical processes in foraging behavior. CEF is based directly on the neural network known as the gated dipole. The gated dipole is capable of carrying out affective reactions to emotionally charged events in line with the opponent process theory of emotion. CEF incorporates a trade-off between foraging and the danger of predation under varying levels of motivation induced by hunger. The results of simulations of foraging decisions indicate that the CEF model is capable of near optimal foraging in a simple patch selection paradigm compared to a random decision rule and a rule of thumb model.