Issues in the comparative cognition of same/different abstract-concept learning

Same/different abstract-concept learning provides a basis for higher order learning. We present criteria (e.g. the use of novel items, how to reinforce responding, achieving full concept learning) for evaluating evidence of abstract-concept learning. We discuss how revealing functional relationships also are critical for understanding how abstract concepts are learned. To illustrate our points, data from six diverse species are presented. The findings reveal quantitative differences in learning with all species achieving full abstract-concept learning. We conclude that same/different abstract-concept learning is an example of convergent evolution shared amongst mammalian and non-mammalian species.