Haptic probing: perceiving the length of a probe and the distance of a surface probed.

Knowing about the properties of objects by wielding them and knowing about the distances of surfaces by striking them with objects as probes are examples of dynamic or effortful touch. Six experiments focused on the invariant mechanical parameters that couple the time-varying states (displacements, velocities) of hand-held rods to the time-varying torques and forces imposed upon them by wielding and probing. There were three major conclusions. First, when a probe is wielded without contact, perceived probe length is a function of the probe's rotational inertia; however, with contact, perceived probe length is affected by the rotational inertia and the distance of the point of contact from the probe's center of percussion. Second, when a surface is struck with a probe, perceived surface distance is affected by the probe's rotational inertia and the angle of inclination of the probe at contact. Third, under seemingly identical conditions of probing, either probe length or surface distance can be perceived selectively without confusion. Results were discussed in terms of haptic information, haptic attention, and the dynamics of probing.     

Haptic probing: Perceiving the length of a probe and the distance of a surface probed

Knowing about the properties of objects by wielding them and knowing about the distances of surfaces by striking them with objects as probes are examples of dynamic or effortful touch. Six experiments focused on the invariant mechanical parameters that couple the time-varying states (displacements, velocities) of hand-held rods to the time-varying torques and forces imposed upon them by wielding and probing. There were three major conclusions. First, when a probe is wielded without contact, perceived probe length is a function of the probe’s rotational inertia; however, with contact, perceived probe length is affected by the rotational inertia and the distance of the point of contact from the probe’s center of percussion. Second, when a surface is struck with a probe, perceived surface distance is affected by the probe’s rotational inertia and the angle of inclination of the probe at contact. Third, under seemingly identical conditions of probing, either probe length or surface distance can be perceived selectively without confusion. Results were discussed in terms of haptic information, haptic attention, and the dynamics of probing.     

Hyperphagia resulting from gut denervation in the sea slug, Pleurobranchaea

Previous research suggests that gut distension by ingested bulk plays an important role in the regulation of food intake in gastropod molluscs. The present study tested whether the bilateral stomatogastric nerves which innervate the esophagus and crop in Pleurobranchaea form a neural pathway carrying information about gut distension to the central nervous system. The posterior branches of the paired stomatogastric nerves were surgically exposed and sectioned in seven experimental animals while the nerves were simply exposed and not sectioned in seven sham-operated control animals. In three, subsequent, daily feeding sessions, the experimental subjects consumed a greater amount of food in terms of percentage of body weight than the control subjects. The experimental animals also gained a greater percentage of body weight and later were found to contain much more food within their guts. The results support the hypothesis that stretch receptors which innervate the gut and which have axons in the stomatogastric nerves form an important negative feedback pathway for the control of feeding in the sea slug.     

Tensorial basis to the constancy of perceived object extent over variations of dynamic touch

Subjects wielded occluded rods, with or without attached masses, and reported the distances reachable with their distal tips. Experiments 1–3 compared wielding about the wrist, the elbow, and the shoulder. Experiments 4 and 5 compared free wielding, using the whole arm, with wielding only about the wrist. The two comparisons, respectively, were of spatial and temporal variations in the rod’s rotational inertia. Perceived extent was found to be constant in both comparisons. This constancy was tied to the inertia tensorI _ij defined about a point that remains a fixed distance from the object during wielding—an invariant of the spatially and temporally dependent patterning of mechanical energy impressed upon the tissues of the body. Discussion focused on the reciprocal action and perception capabilities of multisegmented limbs, the tensorial relations in the neurobiology of dynamic touch, and the strategy of understanding perceptual constancy through invariants.     

Effects of models and demonstrations of personal narratives on the use of lexical ties by writers with mental retardation

A single subject reversal design was used to investigate the effects of two methods for teaching writing to eight adolescents with mild or moderate mental retardation during a weekly process writing workshop. During each workshop, each student wrote a personal narrative while the teacher circulated among the group and provided positive verbal feedback and spelled words on request. Students' texts were later typed with corrected spelling and punctuation and returned to them with verbal praise before the next writing workshop. During the first experimental condition, the subjects listened to an exemplar text selected by the teacher. In the second phase, the teacher read a narrative she had written as the exemplar text. During the third experimental condition, the teacher orally self-instructed herself through steps in writing a narrative. The subjects' texts were analyzed for number of words written and number and type of lexical ties used to produce cohesion between sentences in a text. The model narrative produced the best gains in the number of words written by the poorer readers, while the demonstration improved the cohesiveness of their texts. The better readers and writers wrote more cohesively during the model narrative and produced longer text during the demonstration condition.     

Counseling and screening for cystic fibrosis in patients with congenital bilateral absence of the vas deferens: Patient perceptions

Congenital bilateral absence of the vas deferens (CBAVD) occurs in approximately 1.3% of infertile males and is thought to be, in most cases, a primarily genital form of cystic fibrosis (CF). Fourteen males with CBAVD considering microsurgical sperm aspiration from the epididymis (MESA) and in vitro fertilization were seen for genetic counseling and screening for CF. To retrospectively evaluate these patients' perceptions of the counseling and screening information, we conducted structured telephone interviews to assess their recall of information about CF and its impact on their health concerns and reproductive plans. We found that, as the health implications of CF are abstract and not as important to patients as the diagnosis of CBAVD itself, patients tend to view their CF status primarily in terms of their reproductive potential. Retrospective analysis afforded us an opportunity to identify the psychosocial issues of most concern to this unique patient population.     

Effects of neonatal administration of clomiphene citrate on sexual behavior of female rats: a preliminary report

Female rats were treated with the nonsteroidal estrogen antagonist clomiphene citrate for the first 5 days postpartum. The expectation was that clomiphene would influence the sexual development of these animals as is the case with sexually immature animals treated with steroidal compounds. Analysis showed that treatment with clomiphene completely disrupted the adult sexual behavior of the female. In five consecutive days of testing the experimental females were never observed to mate. They were mounted significantly less often than controls, suggesting that the males were less attracted to them than to normal females. The initial suggestion that clomiphene might affect the sexual behavior of females has been supported; however, further research must be done to identify the underlying mechanism of the change.