FREE RECALL OF REPEATED WORDS AS A FUNCTION OF INTRALIST VARIABILITY

von W right J. M. Free recall of repeated words as a function of intralist variability. Scand. J. Psychol ., 1972, 13 , 39–42.—Five "critical" words were repeated 4 times each in constant positions within lists of 80 items. The number of different filler words, and the order of the repeated filler words, was varied between lists. In free recall tests total recall was approximately constant, but the recall of the critical words was significantly better the greater the variation in the intralist context of these words, especially the greater the number of different filler words. The results are interpreted in terms of the encoding variability hypothesis.     

Rehearsal strategies and the serial-position curve in immediate free recall of ordered items

Immediate free recall of random strings of 10 numbers was studied under four experimental conditions: as each number was presented, subjects either had to recall the previous number (Recall n-1), recall the number just presented (Recall n), read the number (Read aloud), or were silent (Free Recall). Overall recall was the same in all conditions. Recall and order of recall by serial-position changed systematically, with an increasing recency and decreasing primacy effect from Free Recall through Read Aloud and Recall n to Recall n-1. These changes in recall order and serial-position curves suggest that differential rehearsal of items is decreased by requiring retrieval during presentation.     

Estimation of true score and error variance for tests under various equivalence assumptions

Maximum-likelihood estimators of true score variance and error variance for mental tests are derived for six different models of equivalent measurements. Statistical properties of the estimators are examined. Main emphasis is placed upon essentially-equivalent measurements. A statistical criterion for this type of measurement is given. The solution of the comparatively simple maximum-likelihood equations is effected by means of a rapid Newton-Raphson procedure. Two different initial estimators are considered and their relative merits in terms of second moments evaluated. Four numerical examples are appended by way of illustration.Paper read at the Mathematical Psychology Meeting, August 28, 1968, at Stanford, Calfornia.This research was supported in part by the National Institute of Child Health and Human Development, Research Grant 1 P01 HD01762.     

Frequency discrimination near masked threshold

Frequency DLs (Δf) at 1000 Hz were obtained in quiet and under masking conditions similar to those used in pitch-shift experiments, narrow-band noise at levels of 60, 80, and 100 dB SPL and tones at 15 dB SL or less. The Δfs were obtained by means of a tracking task in which the S controlled the input voltage to a frequency modulator. Characteristic improvement was seen when Δf was plotted as a function of sensation level. However, noise level itself was a significant factor, with more intense noise resulting in larger Δfs for tones of equal sensation level re masked threshold. This departure from previous findings is attributed to the signal and noise levels used, although the possibility exists that it is due to the use of modulated tones.     

A response time model for choice behavior

A subject in a two-choice situation characteristically makes several observing responses before performing the final choice. This behavior can be described by means of a random walk model. The present paper explores some possibilities as to how this model can be extended to include choice time. The assumption is made that the duration of each step in the random walk is a random variable which is exponentially distributed. With this assumption, one can predict the probability distributions of the choice times as well as the moments of these distributions.The author gratefully acknowledges his debt to W. K. Estes and C. J. Burke. This study was initiated while the author held a USPHS postdoctoral fellowship at Indiana University.     

A NOTE ON INTEROCULAR TRANSFER AND THE COLOUR OF VISUAL AFTER-IMAGES

Following monocular fixation of a red stimulus figure on a grey background, a projection field having the same colour as the stimulus figure was viewed either with ( a ) the stimulated eye, or ( b ) the non-stimulated eye. In case ( a ) the after-image appeared grey on a red background, but in case ( b ) green or blue, on a red background. In the latter case the brightness and to some extent the hue of the after-image varied when the amount of light coming to the originally stimulated eye varied. The data are in agreement with the assumption that after-images are primarily retinal.     

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.