Attitude and personality characteristics of older stutterers

Attitude and personality characteristics of 29 stutterers (19 male, 10 female) aged 52–82 yr were assessed using five questionnaires. Results indicate that, while the older stutterers score approximately the same as young adult stutterers on scales assessing approach and performance behaviors, the large majority of older stutterers perceive their stuttering as less handicapping than when they were young adults. Self-perceived personality characteristics of the older stutterers were similar to a group of older nonstutterers. While a few of the subjects had experienced some degree of success as a result of treatment later in life, the majority of the subjects did not currently desire treatment.     

The effect of motor preparation on changes in h reflex amplitude during the response latency of a warned reaction time task

Monosynaptic Hoffman reflexes (H reflexes) were recorded from the soleus muscle during the response latency of a warned reaction time (RT) task that required plantarflexion of the foot. The task was done under four conditions of predictability of the response signal (RS), created by the factorial combination of foreperiod duration (1 and 4 s) and variability (fixed and variable). RT varied systematically with RS predictability and was facilitated in conditions that favored prediction of the RS. The response latency was divided into two successive phases by the onset of reflex augmentation: a premotor phase of constant reflex amplitude and a succeeding motor phase marked by progressively increasing reflex amplitude. Reflex augmentation during the motor phase was coupled more closely to the imminent movement than to the preceding signal to respond. The duration of the premotor phase was unaffected by RS predictability, but the duration of the motor phase (like RT) was shorter when the RS was more predictable. The maximum H reflex amplitude reached during the motor phase was greater when the RS was more predictable. The tonic level of H reflex amplitude during the premotor phase was greater in conditions that made prediction of the RS difficult. A second experiment showed that this difference was present throughout the foreperiod. These results suggest that conditions that favor prediction of the RS enhance motor preparation. changes in motor preparation (which affect RT) affect the processes underlying reflex amplitudes in the premotor phase and throughout the preceding foreperiod, in conditions that make prediction of the RS difficult, appear to reflect heightened general arousal.     

Eyewitness testimony and memory distortion

Abstract: Do memories change as we acquire new information? Recent research on memory distortion using implicit tests along with research using confidence is reviewed and new studies are presented. Two new studies asked misinformed subjects to provide reasons for their answers. In each study 15% to 27% of subjects said they remembered seeing items they had only read about. In another study subjects were asked to identify the source of misleading items they had seen in slides or read in misleading questions. Subjects were more likely to say they had seen in slides something they read about in the questions than they were to confuse information from two nearly identical sets of slides. Recent work shows that, not only is it possible to distort memory for events, it is possible to implant an entire memory for something that never happened. The evidence is now clear that we can become mentally tricked into making large as well as small changes in the way we recall the past.     

Similarity ratings and confusability of lipread consonants compared with similarity ratings of auditory and orthographic stimuli.

Similarity ratings of pairs of lipread consonants were obtained using a 5-point scale. Matrices were constructed showing mean similarity ratings and confusions among stimuli. Both the similarity and the confusion data provide normative data useful for researchers in many areas. Lipread data collected here are compared with similarity ratings of orthographically and auditorily presented consonants collected by Manning (1977). These comparisons provide information about how stimulus similarity both within and between presentation formats may affect information processing of the three types of stimuli. These data are of special interest to researchers studying the visual processing of speech and the effect of format of presentation on recall.     

Probabilistic models of language processing and acquisition

Probabilistic methods are providing new explanatory approaches to fundamental cognitive science questions of how humans structure, process and acquire language. This review examines probabilistic models defined over traditional symbolic structures. Language comprehension and production involve probabilistic inference in such models; and acquisition involves choosing the best model, given innate constraints and linguistic and other input. Probabilistic models can account for the learning and processing of language, while maintaining the sophistication of symbolic models. A recent burgeoning of theoretical developments and online corpus creation has enabled large models to be tested, revealing probabilistic constraints in processing, undermining acquisition arguments based on a perceived poverty of the stimulus, and suggesting fruitful links with probabilistic theories of categorization and ambiguity resolution in perception.     

Pathophysiology, prevention, and potential treatment of neural tube defects

Neural tube defects (NTD) remain a major cause of morbidity in spite of the reduction in liveborn incidence with periconceptional folic acid. However, the etiology remains unknown. This article reviews studies that address causation and potential treatment of NTD in humans and in animal models that resemble aspects of the common human NTD. Studies of nutritional markers of vitamin B12 and folic acid support a defect in homocysteine metabolism; a thermolabile variant of methylene tetrahydrofolate reductase, an enzyme that remethylates homocysteine to methionine, correlates with a risk of NTD in some human populations. Numerous mouse mutant models of NTD exist, attesting to the ease of disruption of neurulation, and a genetic basis for this malformation. Of these models, the curly tail mouse mutant most closely resembles the common human NTD. Folic acid does not prevent NTD in this model; however inositol supplementation does result in a significant reduction in incidence. Recent advances in fetal surgery, and evidence from mechanically created myelomeningocele in large animals amenable to surgical intervention suggest that the handicaps associated with myelomeningocele and associated Chiari Type II malformation may be prevented by in utero NTD closure. Success will depend on preservation of neurological tissue until such intervention is possible. Further research in animal models at the genetic and cellular levels, together with technological surgical advances, provide hope that prevention of more NTD and the associated handicaps may be possible. MRDD Research Reviews 6:6-14, 2000.     

The variance of d' estimates obtained in yes-no and two-interval forced choice procedures

In studies of detection and discrimination, data are often obtained in the form of a 2 x 2 matrix and then converted to an estimate of d' based on the assumptions that the underlying decision distributions are Gaussian and equal in variance. The statistical properties of the estimate of d', d' are well understood for data obtained using the yes-no procedure, but less effort has been devoted to the more commonly used two-interval forced choice (2IFC) procedure. The variance associated with d' is a function of true d' in both procedures, but for small values of true d' the variance of d' obtained using the 2IFC procedure is predicted to be less than the variance of d' obtained using yes-no; for large values of true d', the variance of d' obtained using the 2IFC procedure is predicted to be greater than the variance of d' from yes-no. These results follow from standard assumptions about the relationship between the two procedures. The present paper reviews the statistical properties of d' obtained using the two standard procedures and compares estimates of the variance of d' as a function of true d' with the variance observed in values of d' obtained with a 2IFC procedure.