Paper wasps form abstract concept of 'same and different'

Abstract

Concept formation requires animals to learn and use abstract rules that transcend the characteristics of specific stimuli. Abstract concepts are often associated with high levels of cognitive sophistication, so there has been much interest in which species can form and use concepts. A key abstract concept is that of sameness and difference, where stimuli are classified as either the same as or different than an original stimulus. Here, we used a simultaneous two-item same-different task to test whether paper wasps (Polistes fuscatus) can learn and apply a same-different concept. We trained wasps by simultaneously presenting pairs of same or different stimuli (e.g. colours). Then, we tested whether wasps could apply the concept to new stimuli of the same type (e.g. new colours) and to new stimulus types (e.g. odours). We show that wasps learned a general concept of sameness or difference and applied it to new samples and types of stimuli. Notably, wasps were able to transfer the learned rules to new stimuli in a different sensory modality. Therefore, P. fuscatus can classify stimuli based on their relationships and apply abstract concepts to novel stimulus types. These results indicate that abstract concept learning may be more widespread than previously thought.

Keywords: cognition; concept; different; learning; same; wasps.

Figure 1.

(a) Design of the training apparatus. During training, wasps were placed in 3.8 x 3.8 cm balsa wood ‘chambers’ with plexiglass ceilings and either electrified or neutral floors. Each wasp remained in the electrified chamber for 2 min, rested in a dark container for 1 min, and then was placed in the neutral chamber for 2 min. This cycle was repeated four times with different stimuli representing either the same or different relationships. (b) Design of the testing apparatus. During testing, wasps were placed in a balsa wood (for visual stimuli) or glass (for odour stimuli) rectangle with pairs of the same stimulus on one end and pairs of different stimuli on the other end. Learning was tested by measuring whether the wasp entered choice region with either the correct or incorrect stimulus pair over 10 trials. Location of the stimuli were swapped across trials to ensure wasps were responding to the stimuli rather than location. (Online version in colour.)

Figure 2.

Colour, face and odour stimuli. Face stimuli were photographs of local P. fuscatus. Odours were non-volatile hydrocarbons. Stimuli were allocated uniformly across training and testing procedure. (Online version in colour.)

Figure 3.

Mean ± s.e. correct choices made in first transfer tests (dark grey) and second transfer tests (light grey). ‘Transfer test 1’ refers to tests on novel stimuli of the same type as the training stimuli (e.g. novel colours for a wasp trained on colours). ‘Transfer test 2’ refers to tests on novel stimuli of different types (e.g, novel odours for a wasp trained on colours). The dashed line shows the 50 : 50 random expectation. Wasps performed better than chance on all tests, *p < 0.01. There was no difference in accuracy between first and second transfer tests (p > 0.05).