Conspecific and interspecific stimuli reduce initial performance in an aversive learning task in honey bees (Apis mellifera)

Abstract

The purpose of this experiment was to investigate whether honey bees (Apis mellifera) are able to use social discriminative stimuli in a spatial aversive conditioning paradigm. We tested bees' ability to avoid shock in a shuttle box apparatus across multiple groups when either shock, or the absence of shock, was associated with a live hive mate, a dead hive mate, a live Polistes exclamans wasp or a dead wasp. Additionally, we used several control groups common to bee shuttle box research where shock was only associated with spatial cues, or where shock was associated with a blue or yellow color. While bees were able to learn the aversive task in a simple spatial discrimination, the presence of any other stimuli (color, another bee, or a wasp) reduced initial performance. While the color biases we discovered are in line with other experiments, the finding that the presence of another animal reduces performance is novel. Generally, it appears that the use of bees or wasps as stimuli initially causes an increase in overall activity that interferes with early performance in the spatial task. During the course of the experiment, the bees habituate to the insect stimuli (bee or wasp), and begin learning the aversive task. Additionally, we found that experimental subject bees did not discriminate between bees or wasps used as stimulus animals, nor did they discriminate between live or dead stimulus animals. This may occur, in part, due to the specialized nature of the worker honey bee. Results are discussed with implications for continual research on honey bees as models of aversive learning, as well as research on insect social learning in general.

Fig 1. Shuttle box apparatus.

The top image shows a single shuttle box, disconnected from the electronics unit for clarity. Here, the shuttle box is set up for a blue/yellow discrimination. The bottom image is taken from the subject’s perspective inside the shuttle box and shows a stimulus bee in the stimulus chamber.

Fig 2. Correct compartment restriction (CCR) and activity levels in the spatial, shock on blue, and shock on yellow groups.

The left plot shows average CCR values with error bars indicating standard error of the mean. Note the axis is truncated between 20% and 75% to provide a clearer view of the data. The dotted grey line in the center of the graph indicates the 50% chance level of response. The right plot shows average and standard error of activity levels, as defined as the total number of times a bee broke either infrared beam in the center of the shuttle box.

Fig 3. Correct compartment restriction (CCR) and activity levels in the bee baseline, wasp baseline and bee and wasp baseline groups.

The left plot shows CCR values, with the side near the stimulus bee being considered correct, and the side near the stimulus wasp being considered incorrect. Error bars indicate standard error of the mean. Note the axis is truncated between 20% and 75% to provide a clearer view of the data. The dotted grey line in the center of the graph indicates the 50% chance level of response. The right plot shows average and standard error of activity levels, as defined as the total number of times a bee broke either infrared beam in the center of the shuttle box.

Fig 4. Correct compartment restriction (CCR) and activity levels in groups that used another bee as a stimulus.

The left plot shows average CCR values with error bars indicating standard error of the mean. Note the axis is truncated between 20% and 75% to provide a clearer view of the data. The dotted grey line in the center of the graph indicates the 50% chance level of response. The right plot shows average and standard error of activity levels, as defined as the total number of times a bee broke either infrared beam in the center of the shuttle box.

Fig 5. Correct compartment restriction (CCR) and activity levels in groups that used a wasp as a stimulus.

The left plot shows average CCR values with error bars indicating standard error of the mean. Note the axis is truncated between 20% and 75% to provide a clearer view of the data. The dotted grey line in the center of the graph indicates the 50% chance level of response. The right plot shows average and standard error of activity levels, as defined as the total number of times a bee broke either infrared beam in the center of the shuttle box.