The free classification of analyzable and unanalyzable stimuli

The free classification of two-dimensional analyzable and unanalyzable stimuli was investigated. Analyzable stimuli consist of dimensions which are distinct and phenomenally separable (e.g., colored geometric forms); unanalyzable stimuli consist of two dimensions which are not distinct, not phenomenally separable, and which are probably perceived as a unitary dimension (e.g., Munsell colors). In the first experiment, Ss judged the similarity between each stimulus pair for both types of stimuli. The results replicated previous work in showing that the city-block metric was appropriate for the analyzable stimuli and that the euclidean metric was appropriate for unanalyzable stimuli. In the second experiment, Ss classified sets of analyzable and unanalyzable stimuli into two or three groups in any way they wished. For analyzable stimuli, classification was based on the dimensional structure-stimuli which alter the dimensional structure by defining another dimension change classification. For unanalyzable stimuli, classification was based on the similarity structure-stimuli which alter the similarity structure change classification.     

A method for the precise switching of speech

A simple procedure by which a speech signal may be switched on or off (or from one ear to the other) at a precise instant of time is described. The speech sample is first recorded on a magnetic tape loop. A reference pulse is then recorded preceding the speech signal. This reference pulse triggers an adjustable time delay which in tum operates an electronic switch at an appropriate time.     

A device for the easy administration of volatile anesthetics to rats undergoing stereotaxic surgery

Conventional procedures do not provide a practical method for the administration of volatile anesthetics such as halothane to rats while they are undergoing stereotaxic surgery. This paper describes a device which meets this need and which is easy and inexpensive to construct. A two-piece cylinder cut from the mouth of a polyethylene bottle forms a closed system around the muzzle of a rat and does not interfere with the stereotaxic apparatus or with the operation itself. The cylinder is attached to any standard device for the dispension of volatile anesthetics. The immediate advantage is that behavioral assesaments can be made relatively soon after surgery.     

Selective eye movements to simultaneously presented stimuli during discrimination

Human Ss, when given a discrimination task whose stimuli varied in dimension and relevance, always chose and ftxated more frequently the stimulus they had been reinforced for choosing. Decreasing the brightness reduced the choice and ftxation preference for form stimuli over line stimuli and raised total ftxation frequency. Ss decreased fixation frequency to discriminanda with practice.     

Triadic consistency and false heart-rate feedback

Subjects viewed slides of the Rorschach cards while listening to heart sounds that were supposedly but not actually their own. For some of the subjects the heart rate increased when they were exposed to the five achromatic cards and for some subjects the heart rate increased when they were exposed to the five chromatic cards. In addition, some subjects were told that increased heart rate was a sign of mental health (positive condition), and some that the increased heart rate was a sign of mental abnormality (negative condition) Since the heart-rate increase (behavior) and Rorschach cards associated with the increase (attitude object) are connected by a positive causal relation, triadic theory predicts that the sign of the heart-rate increase should generalize to the associated cards (i e, be positive in the positive condition and negative in the negative condition) An analysis of variance revealed such an overall significant effect Closer examination of the data, however, revealed that the triadic effects were not unambiguously occurring when the increased heart rate was associated with achromatic cards It was suggested that in this condition the unique characteristics of the cards facilitated the generation of complicating anxiety. Supportive data for this interpretation were offered     

Effects of uncertain warning signals on reaction time

Three experiments were conducted in an attempt to assess the effectiveness of a warning signal in reducing reaction time when (1) the signal to respond (danger signal) follows the warning signal with a probability less than 1.0, and (2) the interval between warning and danger signals (W-D interval) is variable. The required response was the depression of a foot pedal, as in automobile braking. It was determined that probabilistic warning information could be effective if observers made use of the W-D interval to prepare to make the response required by the danger signal. It was noted, however, that observers differed considerably in their tendency to do this. A model was proposed for describing different response strategies.     

Satiation effects in the perception of single letters’

When single letters were presented for five flashes, with S making a clarity judgment after each exposure, initial potentiation and subsequent satiation effects were found. A processing task and complete prior knowledge led to an increased probability of a “clear” response on the first exposure and to an earlier onset of the satiation effect. The results are discussed in terms of the neural network model underlying this research.     

Carbon dioxide as a reinforcer in escape conditioning

The effects of varying CO₂ concentration, and intervals between CO₂ presentations, were determined from the performance by five pigeons of a learned motor act which eliminates CO₂ from the inspired air. The length of time from the onset of an externally-produced increase in inspired CO₂ to the performance of the learned motor response terminating the CO₂ presentation was inversely related to the CO₂ concentration presented (3 per cent and 5 per cent) and directly related to the inter-trial interval (3 minutes and 1.5 minutes). Chemoreceptors on the ventrolateral surfaces of the medulla are postulated to be the initial site of stimulation in the chain of events leading to the behavioral bioregulation of inspired CO₂ concentration.