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Previous research looking at expectancy in animals has used various experimental designs focusing on appetitive and avoidance behaviors. In this study, honey bees (Apis mellifera) were tested ina series of three proboscis extension response (PER) experiments to determine to what degree honey bees’ form a cognitive-representation of an unconditioned stimulus (US). Tthe first experiment, bees were presented with either a 2 sec. sucrose US or 2 sec. honey US appetitive reward and the proboscis-extension duration was measured under each scenario. The PER duration was longer for the honey US even though each US was presented for just 2 sec. Honey bees in the second experiment were tested during extinction trials on a conditioned stimulus (CS) of cinnamon or lavender that was paired with either the sucrose US or honey US in the acquisition trials. The proportion of bees showing the PER response to the CS was recorded for each extinction trial for each US scenario, as was the duration of the proboscis extension for each bee. Neither measure differed between the honey US and sucrose US scenarios, In experiment three, bees were presented with a cinnamon or lavender CS paired with either honey US or sucrose US in a set of acquisition trials, but here the US was not given until after the proboscis was retracted. The PER duration after the CS, and again subsequent after the US, were recorded. While the PER duration after the US was longer for honey, the PER duration after the CS did not differ between honey US and sucrose US. 

We aimed to examine mechanistically the observed foraging differences across two honey bee, Apis mellifera , subspecies using the proboscis extension response assay. Specifically, we compared differences in appetitive reversal learning ability between honey bee subspecies: Apis mellifera caucasica (Pollman), and Apis mellifera syriaca (Skorikov) in a “common garden” apiary. It was hypothesized that specific learning differences could explain previously observed foraging behavior differences of these subspecies: A.m. caucasica switches between different flower color morphs in response to reward variability, and A.m. syriaca does not switch. We suggest that flower constancy allows reduced exposure by minimizing search and handling time, whereas plasticity is important when maximizing harvest in preparation for long winter is at a premium. In the initial or Acquisition phase of the test we examined specifically discrimination learning, where bees were trained to respond to a paired conditioned stimulus with an unconditioned stimulus and not to respond to a second conditioned stimulus that is not followed by an unconditioned stimulus. We found no significant differences among the subspecies in the Acquisition phase in appetitive learning. During the second, Reversal phase of the experiment, where flexibility in association was tested, the paired and unpaired conditioned stimuli were reversed. During the Reversal phase A.m. syriaca showed a reduced ability to learn the reverse association in the appetitive learning task. This observation is consistent with the hypothesis that A.m. syriaca foragers cannot change the foraging choice because of lack of flexibility in appetitive associations under changing contingencies. Interestingly, both subspecies continued responding to the previously rewarded conditioned stimulus in the reversal phase. We discuss potential ecological correlates and molecular underpinnings of these differences in learning across the two subspecies. In addition, in a supplemental experiment we demonstrated that these differences in appetitive reversal learning do not occur in other learning contexts.