Testing the assumptions of exponential,additive reaction time models

Two assumptions commonly made by choice reaction time (RT) models are (1) that certain experimental tasks can be found that cause an extra processing stage to be inserted into the cognitive process and (2) that the duration of one or more processing stages is random with an exponential distribution. Few rigorous tests of either assumption exist. This paper reviews existing tests and presents several new results that can be used to test these assumptions. First, in the case in which the duration of an inserted stage is exponentially distributed, it is shown that the observable RT density functions must always intersect at the mode of the density requiring the extra processing stage. Second, when only the first assumption (Assumption 1) is made, it is shown that the cumulative RT distribution functions and, in many cases, the hazard functions must be ordered. Finally, when only Assumption 2 is assumed, it is shown that, under fairly weak conditions, the taft of the RT density function must be exponential. The first two results are applied to data from a memory scanning experiment, and the two assumptions are found to receive tentative support     

Mental shock can produce retrograde amnesia

Subjects in three experiments saw a short film of a mentally shocking event in which a young boy is violently shot in the face. Compared to other subjects who saw a nonviolent version of the same film, those who saw the mentally shocking version showed poorer retention of the details of the film. Retention was poorer whether measured by recognition or recall. Furthermore, impaired memory occurred only when the event was mentally upsetting, and not when it was merely unexpected but not upsetting. These results suggest that mentally shocking episodes may disrupt the lingering processing necessary for full storage of information in memory.     

A comparison of mothers' and fathers' speech to their 3-year-old sons

The language patterns of 10 mothers and 10 fathers with their firstborn 3-year-old sons were compared. Ten-minute mother-son and father-son conversations were recorded independently in the home during a free-play session with standard play mterials. The findings of this study indicate that although mothers and fathers used a similar number of utterances in conversing with their sons over a 10-minute period, their patterns of speech were different on a number of quantitative measures including MLU, MLU of five longest utterances, percent of imperatives, and percent of questions. In general, fathers' communication was viewed as more controlling and involving the child less, while mothers' communication was viewed as more child-centered and involving the child more.     

Self-reflection,mood, and helpful behavior

Two pilot studies and two experiments were conducted to test for relationships between mood states, self-reflection, and helpfulness. It was hypothesized that both negative and positive feelings would increase helpful reactions. In the case of negative moods, however, helpfulness would be inhibited if the induced affect engenders self-reflection by associating the bad mood with the person's self-image in a self-referencing process. To test these predictions, female undergraduates read mood-inducing statements that were either (a) negative in content and containing the personal pronoun “I”, (b) negative but not self-referencing, (c) emotionally positive in content, (d) emotionally neutral, or (e) no statements. Afterward, they were asked to complete a questionnaire and to volunteer to participate in a future study. Findings in the first experiment confirmed the hypothesis. Women who had read negative, self-referencing statements were the least likely to comply with a helpful request. The most helpful participants were those who had previously recited the negative, but not self-referencing, and the positive statements. Neutral and control subjects displayed intermediate amounts of compliance with the helping request. Questionnaire results showed that self-reflection was responsible for decreasing the helpfulness of women when negative mood was associated with some aspect of the self. A second experiment successfully replicated the major findings of the pilot studies and the first experiment.     

Cerebral lateralization in individuals diagnosed as autistic in early childhood

Early infantile autism was found to be associated with an atypical pattern of cerebral lateralization. Based on EEG measures of hemispheric activation during cognitive processing, it was found that 7 of the 10 autistic individuals tested showed a pattern of hemispheric specialization rarely seen in the normal population; namely, a “reversal” in lateralization reflective of a lack of left-hemisphere specialization for linguistic functions. Furthermore, the autistic individuals' pattern of cognitive strengths and weakness is suggestive of a selective impairment of the left cerebral hemisphere.     

Vocal changes in stutterers and nonstutterers when speaking to children

Within the last few years, considerable attention has been devoted to the possibility that the amelioration of stuttering in many novel speaking conditions is a function of vocal changes with or without accompanying modifications in prosodic expression. These formulations have made reference primarily to conditions in which stutterers were induced into one or another novel speech pattern by an external stimulus such as masking noise, a rhythmic cue, or by instructions to sing, or read in unison with another speaker. In contrast, far less attention has been paid to other ameliorative conditions that lack a novel external stimulus or special instructions that direct the stutterer to speak in some unique manner. Speaking or reading to a child is an example of this latter type of condition. The present study was conducted to see if nine adult stutterers and a matched group of nonstutterers would evince vocal changes as they read aloud to another adult, a child, and a child and adult together. There was also a fourth control condition wherein the subjects read to one of the experimenters. Dependent measures of disfluency and stuttering, fundamental frequency, fundamental frequency deviation, fluent reading rate, and peak vocal sound pressure level were made and treated statistically. The major findings of this study indicated that, relative to the control condition, both subject groups exhibited several vocal changes when reading to a child alone and to a child and adult together. In addition, the stutterers experienced a reduction in disfluency, but only when reading to the child alone. The normal speakers exhibited too few disfluencies in the control condition for any meaningful change to occur in that dependent variable. The fact that the stutterers evinced vocal changes in both experimental conditions but a significant drop in disfluency in just one bears importantly on hypotheses that emphasize vocal changes in conditions that ameliorate stuttering.