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.     

Recency discrimination predicted from absolute lag judgments

An experiment is described which tests the plausibility of the assumption that two-alternative forced-choice (2AFC) recency discrimination is based on an independent lag estimate of each item. 39 Ss made absolute recency judgments for items (common nouns) at varying lag intervals while an independent group of 74 Ss made 2AFC judgments for pairs of items at comparable lag combinations. It was found that the absolute judgment data generated accurate predictions of 2AFC performance.     

Sensory scales of taste intensity

The subjective intensity of taste was scaled by the method of magnitude estimation in which Os assigned numbers to designate the apparent strength ofstimulus concentrations. Substances used were sucrose, dextrose, maltose, fructose, saccharin, Sucaryl, sodium chloride, and quinine sulfate. For aqueous solutions of each substance, taste intensity was found to increase as a power function of concentration by weight. Some approximate exponents were: sucrose, 1.3; sodium chloride, 1.4; quinine sulfate. 1.0. The magnitude scale for sucrose was compared with the category scale obtained by a commonly used rating procedure. The category scale turned out to be highly nonlinear.     

Verbal interference in a perceptual comparison task

When Ss had to indicate if the colors of pairs of items from the Stroop test were the same or different, the usual interference effect was completely eliminated. However, when the verbal information consisted of SAME and DIFF rather than color names, interference was reestablished. This indicates that the perceptual comparison task does not eliminate interference simply by rendering Ss insensitive to the meanings of words.     

Kinetic disruption of optical texture: The perception of depth at an edge

An examination of the changes in visual stimulation that result from changes in the occlusion of one surface or object by another suggests two hypotheses about the motion-carried information that is sufficient for the perception of the relative depth at an edge as well as the perception of occlusion. Ss’ reports when shown displays containing only this information give strong support to the hypotheses.     

Discrimination learning with and without “errors”

Responses to S− (“errors”) are not a necessary condition for the formation of an operant discrimination of color. Errors do not occur if discrimination training begins early in conditioning and if S+ and S− initially differ with respect to brightness, duration and wavelength. After training starts, S−'s duration and brightness is progressively increased until S+ and S− differ only with respect to wavelength. Errors do occur if training starts after much conditioning in the presence of S+ has occurred or if S+ and S− differ only with respect to wavelength throughout training. Performance following discrimination learning without errors lacks three characteristics that are found following learning with errors. Only those birds that learned the discrimination with errors showed (1) “emotional” responses in the presence of S−, (2) an increase in the rate (or a decrease in the latency) of its response to S+, and (3) occasional bursts of responses to S−.     

An adjusting avoidance procedure with multiple auditory and visual warning stimuli

Male albino rats were trained on an adjusting avoidance schedule in which each lever press accumulated a given amount of shock-free time. Multiple auditory and visual stimuli were programmed for each discrete temporal distance from the shock in an effort to place the avoidance behavior under the control of the shock proximity. The effects of the stimuli were further examined by presenting part of them and then by removing them altogether. With the combined auditory and visual stimuli, the rat spent most of the time relatively close to the shock and usually started to respond only when the shock was near. With the visual stimuli only, the rat kept the shock at intermediate temporal distances and responded more variably. The behavior with the auditory stimuli alone was quite similar to that produced by the combined stimuli, thus indicating that the auditory stimuli exercised the greater control. When all stimuli were removed, the animal usually kept the shock as far away as the procedure permitted. When only a single pre-shock stimulus was presented, the rat remained quite close to the shock and started to respond predominantly in the pre-shock step.     

A method of determining unbiased distribution in the latin square

The paper describes a method of constructing Latin-square designs in which treatment sequences are unbiased with regard to serial order as well as position of treatment. The procedure is useful for those Latin squares in which the number of cells in each column (or row) is an even number, which, when written in ascending and descending series, contain corresponding ordered numbers prime to each other. Such numbers are 2, 4, 6, 10, 12, 16, 18, 22, 28, 30, 36, etc.