The construction of a programmable olfactometer

A new type of multichannel olfactometer is described, and the results are given for gas chromatographical standardization of this equipment. The olfactometer keeps 24 odorous substances available for presentation, consecutively, two per trial, or combinations of the two. It produces concentrations of odorous gas in the air between 1 × l0^?5 and 1 × 10^?11 molecules/liter. The principle of construction is gradual dilution of an odorous gas in streaming purified air. The design provides for electronic control of stimulus sequence and response registration via punched tapes.     

The semiautomatic Wisconsin general test apparatus

A semiautomatic version of the Wisconsin General Test Apparatus is described along with circuitry. Comparison data are provided for the semiautomatic and manual WGTA obtained under comparable procedures and conditions. Response latencies are given for go/no-go object discrimination problems and subsequent retention tests.     

Taste sensitivity in infrahuman species: Use of a genetic model to test the validity of alternative measures

In a genetic analysis of PTC taste sensitivity of mice, Ss were presented tap water and a PTC solution in a two-choice situation. A preference index was used as a measure of taste sensitivity, assuming that ability to taste would lead to avoidance, i.e., negative preference. This assumption, however, lead to the rejection of seven Ss who preferred the test solution. Due to the undesirability of deleting Ss, the data were reanalyzed, using an alternative index of taste sensitivity that required no assumption concerning the hedonic quality of the test solution. Information regarding the inheritance of taste sensitivity to PTC provided the validating criterion for this measure.     

The symmetrical maze: An automated closed-field test series for rats

An automated “intelligence” test for rats is described. Supporting data indicate that this maze-problem series is sensitive to hypothyroidism-induced learning deficit and sex differences. Comparisons between this new problem set and the Rabinovitch-Rosvold (1951) closed-field tests are presented with respect to difficulty, internal consistency, and test-retest reliability.     

The assimilation theory applied to a modification of the Müller-Lyer illusion

The assimilation theory of illusions, which utilizes the principle that large magnitudes in a series are underestimated and small magnitudes are overestimated, was applied to a modification of the Müller-Lyer illusion. A close link was shown to exist between the Müller-Lyer illusion, a modification of the Müller-Lyer illusion, and the Sander parallelogram. In addition, a new illusory target was predicted.     

Sense modality switching and serial leaming

This investigation examined the effect of sense modality switching ofinformation at various positions of a serial learning task. Different numbers of flashes of light and different numbers of “blips” ofa pure tone were used as signalsin a four-position serial learning task. The design of the study involved a switch in sense modality at each one of the four possible positions in the series. Thus, it was possible to determine if the transmission of information through one sense modality makes it progressively more difficult or more time consuming to switch to another source of information transmitted through another modality. The results generally supported the contention that, as information is received through a particular modality, there is a build-up of the disruption involved in switching sense modality.     

Responding under fixed-ratio and multiple fixed-interval fixed-ratio schedules of electric shock presentation

Squirrel monkeys, initially trained under a schedule of electric shock postponement and then under fixed-interval schedules of electric shock presentation, were studied under multiple fixed-interval fixed-ratio and under fixed-ratio schedules of shock presentation. Under the fixed-interval (10-min) component of the multiple schedule, a pause was followed by a gradual increase in responding to a rate maintained until shock presentation; under the fixed-ratio (3-, 10-, or 30-response) component of the multiple schedule, a brief pause was typically followed by a relatively high and uniform rate of responding until shock was presented. When the 60-sec timeout periods, which usually followed shock presentation, were eliminated from the multiple schedule for one monkey, responding was only transiently affected. In the one monkey studied, responding was maintained under a fixed-ratio schedule alone (with timeout periods), but rates of responding were lower than under the fixed-ratio component of the multiple schedule. Characteristic patterns of responding, similar to those engendered under schedules of food presentation or shock termination, can be maintained under fixed-ratio schedules of shock presentation; further, patterns of responding can be controlled by discriminative stimuli in multiple schedules.     

Two-key concurrent responding: response-reinforcement dependencies and blackouts

Two-key concurrent responding was maintained for three pigeons by a single variable-interval 1-minute schedule of reinforcement in conjunction with a random number generator that assigned feeder operations between keys with equal probability. The duration of blackouts was varied between keys when each response initiated a blackout, and grain arranged by the variable-interval schedule was automatically presented after a blackout (Exp. I). In Exp. II every key peck, except for those that produced grain, initiated a blackout, and grain was dependent upon a response following a blackout. For each pigeon in Exp. I and for one pigeon in Exp. II, the relative frequency of responding on a key approximated, i.e., matched, the relative reciprocal of the duration of the blackout interval on that key. In a third experiment, blackouts scheduled on a variable-interval were of equal duration on the two keys. For one key, grain automatically followed each blackout; for the other key, grain was dependent upon a response and never followed a blackout. The relative frequency of responding on the former key, i.e., the delay key, better approximated the negative exponential function obtained by Chung (1965) than the matching function predicted by Chung and Herrnstein (1967).