The effects of random error and subsampling of dimensions on recovery of configurations by non-metric multidimensional scaling

Similarity judgments of three-dimensional stimuli were simulated, with the hypothetical subject attending to only some dimensions of stimulus variation (i.e., subsampling) on each trial. Recovery of the stimulus configuration by non-metric multidimensional scaling was investigated as a function of subsampling, the amount of random error in the judgments, and the number of stimuli being scaled.It was found that: (1) dimensions to which the subject often attends were well recovered even when dimensions seldom attended to were not, and (2) measures of recovery based on interpoint distances were inadequate. Several previous Monte Carlo studies were evaluated in light of the results.This report is based on a thesis submitted in partial fulfillment of the degree of Master of Arts at the University of Illinois. The thesis is an outgrowth of earlier work presented in Cohen, H. S., Wing, P. L., & Jones, L. E. The effects of error and subsampling of dimensions on multidimensional scaling solutions. Mathematical Psychology Meetings, Princeton, September, 1971.     

The effect of set on encoding and rehearsal processes in memory

An experiment was conducted to determine the effect of manipulating S’s preparation for what he will see on a given trial on his ability to mentally keep track of the number of occurrences of each of several different stimuli in a sequence. It was found that, when the same stimuli were used from trial to trial, performance was significantly better than when different stimuli were used. Foreknowledge of the specific stimuli to be used on a given trial did little to improve performance per se, but it did reduce labeling errors. The results were discussed in terms of the “spatial window” model of keeping-track performance.     

Does intermodal equivalence exist between heteromodal stimulus dimensions or between stimulus values on those dimensions?

In a same--different judgement task with successively presented signals, subjects matched dots in different vertical positions and tones of different frequencies intramodally and intermodally. The first and second stimuli of trials in each of the four modality conditions were drawn from a set consisting of two, three or five alternatives. In all intermodal set size conditions, the dimensions of pitch and vertical position were related by the same equivalence rule. While intramodal performance improvement depended only on the total number of practice trials at matching on the relevant dimensions, intermodal performance improvement appeared to be related to the number of trials practice with each heteromodal stimulus pairing in a particular set. After performance had approached asymptotic level neither intramodal nor intermodal matching reaction time depended on set size. Mean “same” reaction time was less than mean “different” reaction time, and this difference was greater for intermodal matching than for intramodal matching. The results indicated that intermodal equivalence exists between discrete stimulus values on heteromodal dimensions rather than between the dimensons themselves.     

Vocational Certainty and Indecision in College Freshmen

Three groups of entering college freshmen, possessing varying degrees of identification of educational-vocational goals, were compared on a variety of personality, achievement, aptitude, school, and family factors. The major differences indicated that the most undecided group was more dependent than the other two groups, but equal to the most decided group in academic achievement, while a middle, or tentatively decided group, was not as successful academically as the most and least decided groups. These findings suggest that educational-vocational indecision has at least two dimensions. A need for different counseling approaches in dealing with uncertain students depending upon the antecedents of their uncertainty is likely.     

Dichotic speech perception: A comparison between stuttering and nonstuttering children

A stop consonant-vowel dichotic listening task was administered to 90 right- handed boys, 30 in each age group of 5, 7, and 9 yr. Half in each group were stutterers, half nonstutterers. Two and a half times as many stutterers as nonstutterers were found to display either a left-ear advantage (LEA) or no ear advantage (NEA). This finding suggested a greater tendency on the part of stutterers, as opposed to nonstutterers, for reversed or bilateral representation of the auditory speech areas of the brain. In addition, both stutterers and nonstutterers displayed significant developmental increases in the number of times they were able to identify both dichotic speech stimuli, thereby supporting the hypothesis of an age-related increase in children's total information processing capacity. The results are discussed in terms of the differences between stutterers and nonstutterers with respect to the issues of motor representation, cognitive modes, and higher-order linguistic processes.     

Bilingual speech: Bilateral control?

Forty bilinguals from several language backgrounds were contrasted to a group of English-speaking monolinguals on a verbal-manual interference paradigm. For the monolinguals, concurrent finger-tapping rate during speech output tasks was disrupted only for the right hand, indicating left-hemisphere language dominance. Bilingual laterality patterns were a function of language used: native (L1) versus second acquired (L2), and age of L2 acquisition. Early bilinguals (L1 + L2 acquisition prior to age 6) revealed left-hemisphere dominance for both languages, whereas late bilinguals (L2 acquired beyond age 6) revealed left-hemisphere dominance only for L1 and symmetrical hemispheric involvement for L2.     

Linguistic recovery after closed head injury

Recovery from acute aphasia after closed head injury was studied in 21 young adults at least 6 months after injury. Three profiles of scores were found using standardized language tests. Persistent expressive and receptive impairment was present in 6 patients who sustained severe diffuse brain injury resulting in global cognitive deficit. Residual expressive impairment, primarily of naming, was associated with mild diffuse brain injury though focal left-hemisphere injury was present in 3 of 6 cases. Patients who recovered to normal levels on all language tests generally had acute neurologic findings consistent with mild diffuse brain injury. Cranial computed tomography at the time of followup frequently disclosed ventricular enlargement.     

Temporal integration and discrimination of equally detectable,equal-energy stimuli: The effect of frequency

Summary The results of several experiments are reported which indicate: 1) complete auditory temporal summation for threshold of up to 32 msec for tones of 493, 1967, and 7874 Hz using a three-alternative forced-choice technique. 2) Equal-energy, equally detectable stimuli constructed of different intensities and durations within the range of complete integration are discriminable from one another. 3) Discrimination level increases as a function of the overall energy level and, consequently, as a function of detection level. 4) When discrimination level is plotted against detection level on normal-normal coordinates, the result is a straight line with a slope (b) greater than unity (1.41b1.68). 5) The extent of the discrimination capability, as well as the slope of the function relating discrimination level to detection level, was found to be independent of the frequency of the tone.All communications regarding this paper are to be addressed to Dr Harvey Babkoff. Dr Babkoff is spending the 1979–1980 academic year at the Military Medical Psychophysiology Laboratory of the Walter Reed Army Institute of Research, Washington, D.C., USAThis material has been reviewed by the Walter Reed Army Institute of Research, and there is no objection to its presentation and/or publication. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense     

Encoding processes and the recall of text

Two experiments investigated the proposition that the amount of cognitive effort expended to encode information will be directly related to recall of that information. While previous research has shown that amount of processing may affect recall, these studies have generally drawn on the notion of an elaborated memory representation to explain their results. In this study, the amount of processing required to correctly interpret anaphoric relations was varied while the elaboration of the memory trace was held constant. These experiments employed a self-paced reading paradigm in which subjects read a series of short paragraphs and later were cued to recall the final sentence of each paragraph. It was found that recall was significantly improved when more processing was required to correctly interpret the anaphoric relationship expressed in the final sentence. These findings suggest that encoding processes can affect recall performance without elaboration of the memory representation.