Extension of the proboscis was conditioned in restrained honeybees with odor as the conditioned stimulus (CS) and sucrose solution-delivered to the antenna (to elicit extension of the proboscis) and then to the proboscis itselfas the unconditioned stimulus (US). In a first series of experiments, acquisition was found to be very rapid, both in massed and in spaced trials; its associative basis was established by differential conditioning and by an explicitly unpaired control procedure (which produced marked resistance to acquisition in subsequent paired training); and both extinction and spontaneous recovery in massed trials were demonstrated. In a series of experiments on the nature of the US, eliminating the proboscis component was found to lower the asymptotic level of performance, whereas eliminating the antennal component was without effect; reducing the concentration of sucrose from 20% to 7% slowed acquisition but did not lower the asymptotic level of performance; and secondorder conditioning was demonstrated. In a series of experiments on the role of the US, an omission contingency designed to eliminate adventitious response-reinforcer contiguity was found to have no adverse effect on acquisition. In a series of experiments designed to analyze the resistance to acquisition found after explicitly unpaired training in the first experiments, no significant effect was found of prior exposure either to the CS alone or to the US alone, although the unpaired procedure again produced substantial resistance that was shown to be due to inhibition rather than to inattention; extinction after paired training was found to be facilitated by unpaired presentations of the US, The relation between these results for honeybees and those of analogous experiments with vertebrates is considered.

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N the early years of this century, when the experimental study of animal intelligence was just getting under way, many different species were brought into the laboratory. From the very beginning, to be sure, there was some preference for the higher animals, but, on the whole, early interest ranged rather widely up and down the phylogenetic scale. Before long, however, the scope of research narrowed. Attention became fixed on a small number of mammalian forms, which were chosen primarily for reasons of convenience, and treated as representative of animals in general, with the cheap and docile rat easily leading all the rest.A set of curves which nicely illustrates this trend was published some years ago by Beach (1950). Based on a count of papers appearing between 1911 and 1948 in the Journal of Comparative and Physiological Psychology and its forerunners, the Journal of Comparative Psychology and the Journal of Animal Behavior, the curves show how interest in the rat mounted rapidly, while interest in the submammalian forms declined. In the thirties, a stable pattern emerged, about 60% of the papers dealing with the rat, about 30% with mammals other than the rat, and about 10% with the lower forms (the submammalian vertebrates and the invertebrates). If we make the computations required to bring these curves up to date, we find no significant change in the state of affairs decried by Beach a decade ago. Please note that Beach's curves are based on all papers published in a single journal. If we count only the papers on learning, and look at a broader sample of journals, the effect becomes even more striking. About 90% of our work on animal learning has been done with the rat.Of course, specialization has its advantages, and, if the process of learning were essentially the same in all animals, it would be rather improvident of us

As an alternative to a symbolic interpretation of transitivity in the discriminative performance of pigeons, a modified reinforcement theory (value transfer theory) was proposed by Fersen, Wynne, Delius, and Staddon (1991). Its novel assumption was that the value of the negative member of a pair of stimuli with which an animal is trained is enhanced by the value of the positive member of the pair. In this article, that assumption is shown to be unnecessary. All of the transitivity data for pigeons can be simulated with a simple conditioning model developed for honeybees that retains the conventional independence assumption.