Time discrimination training of laboratory animals using a PDP-8 computer

The purpose of this paper Is to describe the use of a small, general-purpose digital computer system in the training of laboratory animals to discriminate stimuli on the basis of their duration. The computer hardware and software required for such training, together with some illustrative results from two recent studies, will be described.     

An olfactory discrimination procedure for mice

This paper describes an olfactory discrimination procedure for mice that is inexpensively implemented and leads to rapid discrimination learning. Mice were first trained to dig in small containers of sand to retrieve bits of buried chocolate. For discrimination training, two containers were presented simultaneously for eight trials per session. One container held sand mixed with cinnamon, and the other held sand mixed with nutmeg. Both containers were baited with chocolate buried in the sand. One odor was designated S+, and mice were allowed to dig and retrieve the chocolate from this container. The other odor was S-, and both containers were removed immediately if subjects began to dig in an S- container. After meeting a two-session acquisition criterion, subjects were given a series of discrimination reversals. In Experiment 1, 12 Swiss-Webster mice (6 male and 6 female) acquired the olfactory discrimination in three to five sessions and completed 3 to 10 successive discrimination reversals within a 50-session testing limit. In Experiment 2, subjects were 14 Pah(enu2) mice, the mouse mutant for phenylketonuria; 7 were homozygotes in which the disorder was expressed (PKU), and 7 were heterozygotes with normal metabolism (non-PKU). Thirteen mice completed pretraining in four to seven sessions, acquisition required 3 to 12 sessions, and all mice completed at least three reversals. Learning rates were similar in PKU and non-PKU mice. We discuss issues related to implementation and several potentially useful procedural variations.     

A microcomputer-controlled system for measuring reactivity in small animals

A microcomputer-controlled system has been designed for measuring reactivity in small laboratory animals. This system uses a microcomputer to trigger an acoustic signal, which is fed to a loudspeaker through an audio power amplifier. An animal’s acoustic startle response is recorded using a moving-coil loudspeaker as a movement transducer. The transducer output is coupled to a peak-hold circuit that records the maximum voltage generated by the animal’s response. After conversion to digital form, the data for each stimulus presentation are stored and then printed when all trials have been completed.     

Solomon design analysis of multiple-choice Rorschach animal content

The Solomon four-group design was used to study the effects of a persuasive message on a selected multiple-choice Rorschach index--animal content. The independent variable elicited behavior in a predictable manner. Pretesting as a main effect was not significant, but as an interactional effect obviated the effect of the persuasive message. Although knowledge of test rationale can elicit behavior that conforms to experimental demand characteristics, some subjects nonetheless acted in defiance of such information. A condition for defiance in this experimental arrangement, however, was pretesting. Other possibilities regarding the study of compliance behavior and the use of pathognomonic indicators were suggested. Ethical issues were raised.     

Generalization of auditory intensity as a function of small amounts of discrimination training

Rats were trained on a two-valued auditory-intensity discrimination for 5, 2, 1 or 0 days. Then, the bar-press response rate was sampled in the presence of seven added discrimination stimuli (generalization) for seven days. Daily training sessions were 4 hr in length throughout the experiment. Only the five-day group exhibited a marked superiority on the multi-valued discrimination when contrasted with the group having had no prior simple discrimination training.     

A discrete-trials/fixed-interval method of discrimination training

An efficient new method of discrimination training is described which has several advantages over older free-operant and discrete-trials procedures. Illustrative data on reversal learning in pigeons and goldfish are presented.     

A digital system for recording startle,responses in small animals

An easily constructed, isometric startle-recording system is described. The animal enclosure is attached to a plywood board-which, in ten, is mounted in a “springboard” arrangement. Movement is detected by a phonocartridge mounted beneath the chamber, and a digital record of this movement is obtained through the use of a voltage-to-frequency converter. A brief experiment in which the system was used to assess the rat’s reaction to electric footshock is also presented.