Inferential reasoning abilities in wild-caught bumblebees

Abstract

The ability to make a decision by excluding alternatives (i.e. inferential reasoning) is a type of logical reasoning that allows organisms to solve problems with incomplete information. Several species of vertebrates have been shown to find hidden food using inferential reasoning abilities. Yet little is known about invertebrates' logical reasoning capabilities. In three experiments, I examined wild-caught bumblebees' abilities to locate a 'rewarded' stimulus using direct information or incomplete information-the latter requiring bees to use inferential reasoning. To do so, I adapted three paradigms previously used with primates-the two-cup, three-cup and double two-cup tasks. Bumblebees saw either two paper strips (experiment 1), three paper strips (experiment 2) or two pairs of paper strips (experiment 3) and experienced one of them being rewarded or unrewarded. At the test, they could choose between two (experiment 1), three (experiment 2) or four paper strips (experiment 3). Bumblebees succeeded in the three tasks and their performance was consistent with inferential reasoning. These findings highlight the importance of comparative studies with invertebrates to comprehensively track the evolution of reasoning abilities, in particular, and cognition, in general.

Keywords: bumblebees; inferential reasoning; invertebrates; logical reasoning.

Figure 1.

Representation of the experimental conditions (Direct and Exclusion cues) for the (a) two-strip, (b) three-strip and (c) double two-strip paradigms; experiments 1, 2 and 3, respectively. Bees faced two (experiment 1), three (experiment 2) or four objects (experiment 3) and experienced one of them dipped in sucrose (Direct cue condition) or in water (Exclusion cue condition). The bees’ task was to search among the objects when presented a second time (Choice array). For each experiment, the position of the target strip is counterbalanced across trials—as represented in (a). In experiment 2 (b), the pair of strips that contained the target strip was counterbalanced across subjects. In experiment 3 (c), for each subject, the target strip could be in pair A or B, and this was counterbalanced across trials. See electronic supplementary material, figure S1 for a representation of the Familiarization and Control conditions of experiments 2 and 3.

Figure 2.

The percentage of correct responses in the Direct cue and Exclusion cue conditions of experiment 1 (two-strip paradigm) and experiment 2 (three-strip paradigm), respectively. For experiment 3 (double two-strip paradigm), only the percentage of correct responses in the Exclusion cue condition is represented. The percentage of correct responses was calculated out of the trials performed for each bee. The individual percentages were then used to calculate the group mean. The asterisk indicates the conditions in which bees performed significantly above chance. The bars represent the s.e.m.