Magnitude and frequency of reinforcement and frequencies of interresponse times

The relative magnitude and relative frequency of reinforcement for two concurrent interresponse times (1.5 to 2.5 sec and 3.5 to 4.5 sec) were simultaneously varied in an experiment in which pigeons obtained grain by pecking on a single key. Visual discriminative stimuli accompanied the two time intervals in which reinforcements were arranged by a one-minute variable-interval schedule. The resulting interresponse times of each of three pigeons fell into two groups; "short" (1.0 to 2.5 sec) and "long" (3.0 to 4.5 sec). Steady-state relative frequencies of these interresponse times were orderly functions of both reinforcement variables. The combined effects of both independent variables were well summarized by a linear function of one variable, relative access to food. Unlike corresponding two-key concurrent variable-interval schedules, the present schedule did not produce an equality between the relative frequency of an operant and either the relative magnitude or the relative frequency of reinforcement of that operant. A tentative account is provided for this difference between one-key and two-key functions.     

A note on the up-and-down method

Objections to the use of the original version of the up-and-down method in psychology, as exaggerating individual differences and yielding discrepant results, overlook statistical, psychometric, and logical factors. When the method is applied incorrectly, the standard error of SD is largeand apparent differences in estimates of SD are not statistically significant. Psychometrically, a singletrial procedure should give less reliable, hence more variable. PSEs than one using multiple trials. But this effect increases standard error of the mean. thus significant mean differences found with the method are not attributable to greater variability in PSEs. Explanations of discrepancies in results from up-and-down and traditional methods in the study of perceptual development fail to account for numerous similarities. Finally, a novel method ought to produce some novelty, if it is to make a contribution to psychology,     

Visual search under conditions of very rapid sequential Input rates

The purposes of the present experiment were to provide information on rate of information processing in visual perception and to determine the degree to which the “sequential blanking” effect found by Mayzner. Tresselt, and Cohen (1966) constituted a limitation on rapid sequential input rates. A 10-channel tachisto scope was employed that permitted controlled durations of each of the 10 channels and the 9 inter channel intervals. The S’s task was one of visual search or detection in which he searched for a target letter among noise letters. A temporal interval forced-choice procedure was used. In addition to varying the rate at which letters were sequentially presented, various irregular temporal spatial orders of presentation of the letter sequences were employed and the direction and orientation of the display in the visual field was varied as was also the spacing between adjacent stimuli. No evidence of “sequential blanking” was found either in terms of the detection criterion or in the Ss’ phenomenal reports. Detection performance was as good at a rate of 2 1/2 msec per letter as it was at a rate of 30 msec per letter.     

Further studies on the psychophysics of irregular nerve action potential patterns

In this paper we consider two problems concerning human psychophysical discriminability of variable interval nerve action potential patterns. The first question asks which of two possible alternatives-additional sample size or elongation of duration-is responsible for the improvement in performance as the number of pulses in a stimulus train increases. Our data strongly indicated that the answer to this question is increased sample size. The second question concerns what effect, if any, parallel rather than serial presentation of the two alternatives in a forced choice psychophysical test will have on the function relating interpulse interval and discriminability. The answer to this question appears to be that other than a slight elevation of the absolute levels no changes in the general form of the response is produced.     

Luminance thresholds for the Bezold-Brücke hue shift

This study presents data on the luminance difference at which a hue difference is first perceived between two identical spectral lights. Thresholds were obtained for both luminance increments and decrements from a 2.00 log troland standard for wavelengths between 470 nm and 690 nm. A predicted luminance threshold for each wavelength was calculated based on wavelength discrimination data and the Purdy constant hue contours; i.e. that luminance at which the constant hue contour intersects the wavelength discrimination bound for a given wavelength. A generally good agreement was obtained between observed and predicted values.     

On translating logic

The paper comments on Dummett's Significance of Quine's Indeterminacy Thesis and discusses Quine's views on the translation of logical connectives. Some difficulties about the latter related to those raised by Morton (J. Phil. 70 (1973), 503–510) are considered. Quine seems here to be in a position considered by Dummett of not allowing a foreigner to be translated as conflicting with one's own firm theoretical commitment (in this case classical logic). But Dummett seems wrong in holding that entrenched theoretical statements must be stimulus analytic.A revised and expanded version of remarks at the Conference on Language, Intentionality, and Translation Theory, University of Connecticut, Storrs, March 2, 1973, commenting on Michael Dummett, The Significance of Quine's Indeterminacy Thesis. I am greatly indebted to the discussion at the Conference.     

Air flow characteristics of the speech of stutterers and non stutterers

This study involved respirometric measurements of six normals and six stutterers throughout vocal and whispered readings of 12 CVC words. In each condition, dependent variables were peak air flow rates on initial and final consonants, flow duration and flow volume between peaks. The stutterers, both individually and as a group, were almost completely fluent during the readings in both conditions. At the same time, their air flow, duration and volume scores either equalled or exceeded those of the controls. These results are discussed in terms of how air flow and durational features of articulation contribute to fluent speech. Directions for future work are also described.