Abstract
Interval timing is a key element of foraging theory, models of predator avoidance, and competitive interactions. Although interval timing is well documented in vertebrate species, it is virtually unstudied in invertebrates. In the present experiment, we used free-flying honey bees (Apis mellifera ligustica) as a model for timing behaviors. Subjects were trained to enter a hole in an automated artificial flower to receive a nectar reinforcer (i.e. reward). Responses were continuously reinforced prior to exposure to either a fixed interval (FI) 15-sec, FI 30-sec, FI 60-sec, or FI 120-sec reinforcement schedule. We measured response rate and post-reinforcement pause within each fixed interval trial between reinforcers. Honey bees responded at higher frequencies earlier in the fixed interval suggesting subject responding did not come under traditional forms of temporal control. Response rates were lower during FI conditions compared to performance on continuous reinforcement schedules, and responding was more resistant to extinction when previously reinforced on FI schedules. However, no “scalloped” or “break-and-run” patterns of group or individual responses reinforced on FI schedules were observed; no traditional evidence of temporal control was found. Finally, longer FI schedules eventually caused all subjects to cease returning to the operant chamber indicating subjects did not tolerate the longer FI schedules.
Highlights
A sense of time appears to be of fundamental importance for animals and can be observed in the ubiquity of circadian rhythms in species of the animal kingdom
Drop-out percentages during shorter fixed interval (FI) schedules reiterate the need for an individual analysis rather than an aggregate group analysis as multiple patterns of responding occurred in each group
Based on the findings reported in [21], we predicted bees exposed to higher FI schedules would have a higher response rate in extinction than subjects only reinforced on continuous reinforcement (CRF)
Summary
A sense of time appears to be of fundamental importance for animals and can be observed in the ubiquity of circadian rhythms in species of the animal kingdom. The molecular underpinnings for circadian rhythms appear to have arisen more than once in the early evolution of life [2]; circadian rhythms have been shown to increase fitness in organisms as simple as cyanobacteria [3], [4]. Perception of time intervals that are shorter than circadian rhythms is important for animal fitness. Many aspects of escaping predators depend on interval timing (e.g. evasive moves are unsuccessful if they occur too early or too late) [8]. Competitive interactions involving reproduction may rely on interval timing for some species when communication is involved [9]
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