An indirect method of measuring perceived distance from familiar size

Two methods of measuring perceived distance as a function of familiar size were compared in five experiments. The method which uses the perception of motion concomitant with a motion of the head, unlike the method of verbal report, is considered to provide a measure of perceived distance that is unaffected by factors of cognitive distance. The results of the experiments indicate that although the perceived egocentric distance of an object can vary somewhat as a function of the cue of familiar size, the larger variation often found with verbal reports of distance is based upon cognitive, not perceptual, information. The cognitive information is interpreted as resulting from the perception of the object as off-sized and the observer’s assumption that the perceived size of an object will vary inversely with its physical distance.     

Development and evaluation of a microcomputer testing terminal for testing and instruction

This paper describes the development and evaluation of the hardware and software of a stand-alone microcomputerized testing terminal. The microterminal represents a viable way of conducting and scoring multiple-choice tests and reliably obtains this information for presentation to a centralized management computer system. Obligating informational presentation to regular programmed materials and eliminating the need to handle constructed responses removes the requirements for large display features, thus contributing greatly to the low-cost feature of the microterminal.     

A rapid and sensitive method for measuring the conditional emotional response II: On-the-baseline excitatory conditioning and extinction

The present study outlines a rapid and sensitive on-the-baseline conditional emotional response (CER) procedure. Using rats as the experimental subject, the method detects delay conditioning, incubation, extinction and spontaneous recovery. In addition, the method detects conditional responding using electric shock ranging from 0.23 to 0.50 mA as the unconditional stimulus. Because of its speed and sensitivity, the method shelters the subject from unnecessary long-term deprivation and pain.     

Large and rapid improvement in form discrimination accuracy following a location precue

Processing of a visual stimulus can be improved by precuing its location. Most previous precue studies have used reaction time as the dependent measure and have found large effects; but when form discrimination accuracy has been used, precue effects have been relatively small. The present experiments yielded large, short-latency precue effects on form discrimination accuracy. A small square precue was briefly presented near one of four possible target locations. Then one of four possible targets (T-like figures) was presented in each location, followed by a mask. Observers attempted to identify the target that had been presented in the cued location. In experiment 1, target duration, cue-to-target distance, and cue-target onset asynchrony (SOA) were varied. Target discriminability (d') increased markedly with increasing precue-target SOA, even at very short SOAs. Thus, there was no evidence for a delay in the onset of precue effects (caused, for example, by the need to shift attention across the visual field). Performance was best for precues that were closest to the target, thus ruling out a forward masking explanation of the effect. Finally SOA and target duration interacted strongly - longer precue SOAs resulted in larger effects of target duration. In experiment 2, this interaction was replicated using an additional target duration and longer SOAs. One interpretation of this result is that focal attention increases the rate at which information can be extracted from a visual location.     

Visual size difference discrimination: Effect of disc size and retinal locus

Ability to discriminate between the sizes of two adjacently presented discs of light is considered both as a function of the size of the discs and the retinal locus of their presentation. Ss were required to report whether a comparison disc was seen as larger or the same size as a standard disc when the two were presented briefly together. Results showed that the and required for 50% difference discrimination was independent of the size of the disc and was constant at about 30 sec of arc. For peripheral presentations, the jnd was found to increase in a linear manner with increasing eccentricity of presentation. Comparisons are drawn between the results obtained and peripheral visual acuity data and it is speculated that similar processes are involved in both situations.     

Whisker-based discrimination of object orientation determined with a rapid training paradigm

Rats use their large facial whiskers to discriminate the spatial features of objects. Despite numerous electrophysiological recording studies in the central trigeminal whisker representations that document neurons tuned to the direction of whisker deflection, there is no behavioral evidence to date that rats can use their whiskers to discriminate between object orientations. In the present study, we characterized whisker-dependent orientation discrimination using a one-trial learning procedure. Sprague-Dawley rats were trained and tested in a three-arm 'Y-maze' that was outfitted with 180 independently moveable bars that protruded into the arms of the maze to contact the whiskers. On the first day, the maze was configured to have two arms with only horizontal bars and a third arm with only vertical bars and rats were allowed to freely explore all arms. On the second day, rats were isolated in one arm that contained only vertical bars as a conditioned stimulus (CS) and administered three mild foot shocks. On the third day, the maze was configured identically to the first day and rats were once again allowed to freely explore the maze. We measured the percentage of time spent in each arm of the maze and found that most rats spent significantly less time in the arm containing the CS after training compared to before training. Subsequent control experiments determined that the conditioned avoidance was attributable to orientation cues, was caused by the association of the conditioned and unconditioned stimulus and was whisker-dependent. Avoidance behavior was significantly reduced when the difference between the conditioned and non-conditioned orientation difference was reduced to 45 degrees. Thus, rats can discriminate object orientation with their whiskers and an estimate of their discrimination thresholds can be rapidly acquired through the application of a one-trial learning paradigm.     

A tactile stimulation device for measuring two-point and gap discrimination thresholds in humans

A device to measure two-point-discrimination and gap-discrimination thresholds is described. The apparatus is capable of controlled and reliable delivery of forces up to 42.50 g while determining point of skin contact and subsequent depth of skin indentation during threshold determination. Stimulus delivery is controlled by computer software that deactivates a solenoid, allowing a counterbalanced beam with one of two stimulus wheels mounted on its end to rise and stimulate the skin. Depth of skin indentation is recorded by hardware that monitors the output of a photocell reflecting the position of the beam. The apparatus allows complete computer control of all data acquisition and recording.     

A portable pupilometer system for measuring pupillary size and light reflex

A new pupilometry assessment system was evaluated as an instrument for potential use in basic research and clinical studies of addictive drug use in humans. The system is portable and can be used as a peripheral device with a variety of IBM-compatible personal computers. The pupilometer electronically measures the pupil diameter with infrared sensors and has the ability to stimulate the pupil with a programmable pulse of light and to record the resultant papillary response. The present report compares the static pupil-diameter measurements obtained with this infrared pupilometer and those obtained photographically in a bench-top and in a clinical setting. The infrared pupilometer was also used to record the light reflex of the pupil in research subjects after administration of various morphine-related drugs. The results indicate that static pupil-diameter measurements made with the infrared pupilometer compare favorably with the photographic measurement. The ability of the infrared pupilometer to record the light reflex may provide an additional means of quantitatively measuring drug action.     

Development of a method for increasing the utility of multiple correlations by considering both testing time and test validity

A modification of the Wherry-Doolittle test selection method is presented by which tests are included in a multiple correlation (obtained for a given battery of tests) in the sequence in which the rate of return in validity per unit of testing time is greatest, rather than in the order of the size of their contribution to the multiple correlation. It is proposed that the modified method can be utilized profitably when there are economic or practical limits on the time available for test administration.The major portion of this article is based upon a thesis by W. F. Long directed by Dr. Joseph Tiffin with the counsel of Dr. Irving W. Burr. This thesis was submitted in partial fulfillment of the requirements for the degree of Master of Science in Psychology, Purdue University, June, 1947.