Stimulus-dependent emergence of understanding the 'same-different' concept in budgerigars

Abstract

The ability to understand relational concepts, such as 'same' and 'different', is a critical feature of human cognition. To what extent non-human animals can acquire such concepts and which factors influence their learning are still unclear. We examined the acquisition and the breadth of understanding the 'same-different' concept in budgerigars (Melopsittacus undulatus). Budgerigars trained to discriminate stimulus pairs in which two identical figures were either the same or different size (Experiment 1) successfully generalized the discrimination to novel stimuli belonging to various categories (size, colour, shape, geometric type and number of dots). The results of Experiment 1 thus demonstrate that budgerigars can perceive and generalize the same-different concept across dimensions after training with a limited set of stimuli differing along a single dimension. In contrast, while most budgerigars trained to discriminate two pairs of discs that were either the same or different in colour (Experiment 2) could generalize the discrimination to novel stimuli within the training category (colour), only few generalized the discrimination to another category suggesting a generalization based on perceptual similarity. The results thus show that whether budgerigars generalize a relationship by conceptual or perceptual similarity depends on the nature of the training stimuli.

Keywords: budgerigar; cognition; relational concept learning; same–different.

Figure 1.

Training and test stimuli of Experiments 1 and 2.

Figure 2.

Photos of the experimental set-up (a) Apparatus for the experiments. (b) Bird discriminating achromatic stimuli. (c) Bird discriminating colour stimuli.

Figure 3.

Individual learning performances during the training. (a) Mean percentage of correct responses to the eight stimulus pairs for the ten birds in Experiment 1. (b) Mean percentage of correct responses to the eight stimulus pairs for the ten birds in Experiment 2. Bars show 95% CI.

Figure 4.

Performance in the tests during Experiment 1. (a) Percentage of correct choices in the five tests with novel stimuli of size, shape, geometric type and colour (mean ± s.e., n = 5). *Correct responses are significantly higher than the chance level of 50% (p < 0.05). (b) Individual performances in the five tests.

Figure 5.

Performance in the tests during Experiment 2. (a) Percentage of correct choice in the five tests with novel stimuli of size, shape, geometric type and colour (mean ± s.e., n = 10). *Correct responses are significantly higher than the chance level of 50% (p < 0.05). (b) Individual performances in the five tests.