Polysemy and memory

The degree of ambiguity of words with multiple meanings was estimated by the semantic uncertainty (U) of a word as measured by word association and sentence generation tasks. Ambiguous words defined in this way were as well remembered in a recognition memory test as control words. When words were first presented in sentences that would determine their encoded sense, it was found that successive encodings of an ambiguous word converged more when the word appeared in its primary sense than when it appeared in its secondary sense. However, given convergent encodings, recognition was more likely if the word had first occurred in its secondary sense. An explanation in terms of semantic focus is offered and related to the general relationship between recognition and frequency.The research reported in this paper was supported by the Learning Research and Development Center, which is supported in part by the U.S. Office of Education.     

The importance of being first: A tachistoscopic study of the contribution of each letter to the recognition of four-letter words

Three studies investigated the effect on the response time for voicing a four-letter word of delaying one of the letters or the entire word for intervals of up to 500 msec. Experiment I found delay of the first letter most detrimental, while delay of the second, third, or fourth letter facilitated performance. Experiment II confirmed these findings and indicated that delay of the entire word produced response times similar to delay of the first letter. Experiment III investigated the possibility that knowledge of the pronunciation of the first letter was the essential factor in facilitating performance when later letters were delayed. It was concluded that when pronunciation of the first letter was known, Ss were able to begin processing the word immediately.     

Decision making and the P300 component of the cortical evoked response

The amplitude of P300, and of other components of the evoked potentials, was examined during a task which required Ss to make a response appropriate to the conjoint properties of two rapidly successive visual patterns. In one set of conditions, the task was structured such that both stimuli were needed for the choice judgment. In another set of conditions, the task was changed from choice to simple RT by presenting the patterns in a predictable order. It was observed that P300 was enhanced during the choice RT conditions and that this enhancement was present only for the P300 following the stimulus permitting the choice and not the other, relevant but not decisive, stimulus appearing in close temporal proximity. An appreciable degree of independence between P300 and other components was indicated by the appearance of P300 under conditions in which other evoked potential components were entirely refractory. The data support an account for P300 in terms of poststimulus processes, such as decision making, and not in terms of preparatory adjustments.     

Size judgment: The presence of a standard increases the exponent of the power law

Ss judged the size of circles by the methods of magnitude estimation and magnitude production, with or without a standard figure present. The presence of the standard raised the exponent of the power law. The effect was largely independent of the position of the standard in the range of stimuli. It is argued that the standard’s effect was not mediated by a difference in apparent size between perceived and remembered standards, a change in Ss’ response strategies, a decrease in sequential dependencies, or other previously identified bias effects.     

Direct observation and automated scoring of the activity of active and inactive inbred mouse strains

Inbred mouse strains previously found to be low (A/J) and high (C57BL/6J) in open-field activity were tested in a plastic oval runway while their runway activity was directly observed and also monitored by a contact switch recording device. The activity of active C57BL/6J mice was accurately monitored by the recording device, but scores of inactive A/J mice were inflated by a factor between 2 and 3 X. Activity differences between strains were consistently maintained[during repeated tests under both high and very dim illumination if direct observational scores were used. Utilization of scores obtained by the automated recording device resulted in a failure to obtain group differences under the condition of dim illumination. These results were directly related to the mode of locomotion of the two mouse strains.     

Interocular non-independence

Binocular interaction was studied by presenting a different letter form to each eye via a dichopic tachistoscope. The two dissimilar letters were presented simultaneously or at short delay internals of 0–200 msec and were either presented on corresponding or non-corresponding retinal areas. At delay internals of less than 100 msec stimulation of corresponding areas resulted in identification performance below that to be expected on the basis of independent chances to perceive. Stimulation on non-corresponding areas resulted in both presented letters being identified at the accuracy level predicted by an independence assumption.     

Motivated changes of auditory sensitivity in a simple detection task

Recently both neurophysiological and psychophysical theories have suggested that the sensitivity of receptors, or of the whole organism, may change through “efferent control” or as a result of “motivation.” A psychophysical method has been devised to investigate changes in a listener’s ability to detect signals in a noisy background, which are elicited “on demand” by the E, and when the time course of the changes may be in the order of seconds rather than minutes orhours. Observed effects, which are consistent with the hypotheses of active control of sensitivity, are found to be orderly but quite small, generally less than that associated with a 1–2 dB increase in the level of a tonal signal. While the average increment in performance is thus slight, it is found that the variance between Ss is significantly reduced when strong motivating stimuli are introduced. This reduction in variance may reflect an upper limit on the performance of real listeners, which might be fruitfully compared with the theoretical limits proposed in the theory of signal detectability.     

Use of Control Groups in Studies of Guidance

Problems in the interpretation of results of studies in which control groups are used are illustrated in a follow-up study. Subjects who had been counseled over a four-year period at the Research and Guidance Laboratory for Superior Students at the University of Wisconsin were followed up four years after high school graduation and their performances were compared with those of the members of a control or comparison group. The results are presented and the adequacy of the control group technique is discussed. The validity is questioned of the commonly accepted procedure of selecting control group subjects on the basis of their current comparability with experimental subjects without adequate history of their development toward that status.