Conditional relations by monkeys: Reflexivity, symmetry, and transitivity

Two cynomolgous macaques categorized six colors into two groups of three after conditional discrimination training (zero-delay symbolic match-to-sample). The procedures resulted in the establishment of relations among the elements of each set-relations that were not specifically trained and that can be characterized by the properties of reflexivity, symmetry, and transitivity. Each set of colors was related to a characteristic pattern of responding: One response pattern involved temporal duration (press and hold the response keys); the second response pattern entailed repeated pressing and releasing of the response keys (fixed ratio 8). Six combinations of two colors were trained, three combinations from each set. After discriminative performance stabilized for each monkey, they were tested with 10 additional color combinations, all of which differed from the training combinations. The conditional relations established between test combinations can be characterized as stimulus equivalence. The training procedures were analogous to the procedure of using category names, and have implications for understanding the function of language in the formation of equivalence classes.     

Malthus's Essay on Population: the facts of "super-growth" and the rhetoric of scientific persuasion

For the Malthusian theory of population to be accepted as "scientific," it was essential that the theory be established on wide empirical evidence. A close examination of the "facts" provided by Malthus, however, shows that many of his crucial facts are based on distortions of the available evidence. Malthus was probably aware of much of this weakness, but for rhetorical reasons he persisted with the sandy empirical foundations from which he began.