Accommodation fatigue and dark focus: The effects of accommodation-free visual work as assessed by two psychophysical methods

Past studies of accommodation fatigue have yielded inconsistent results, partly because they have not used direct measures of accommodation, and partly because they may have been based on a misleading conception of the nature of accommodation. The dual-innervation theory of accommodation suggests that the resting position of accommodation may be neuromuscular rather than just muscular, and that it lies not at optical infinity, as assumed by older conceptions, but at some intermediate position (dark focus). Among the predictions that may be deduced from this theory is that long-term visual work not requiring active accommodation will not induce fatigue. The present study involved continuous measurements of dark focus for 10 young adults over a 3-h period, using the laser optometer with two psychophysical procedures Ibracketing and staircase. Consistent with the prediction, no changes in dark focus were found, in spite of the demanding visual task. Furthermore, it was found that both psychophysical methods yielded essentially identical results. The practical and theoretical implications of these results are discussed, and recommendations are given regarding situations in which each of the psychophysical methods is likely to be most useful.     

Glutamate as a transmitter in the CNS and its presumed significance in the pathogenesis of cerebral seizure forms--recent aspects

Glutamate is believed to be quantitatively the most outstanding of the excitatory transmitters in the CNS. Certain conformationally related analogues, e. g. kainate, N-methyl-D-aspartate, ibotenate, and homocysteate, act as glutamate agonists. The local or systemic administration of these "excitotoxic" compounds induces epileptiform activity pointing out new and deeper insights into the epileptic process. Additionally, the glutamate transmitter hypothesis is expected to give a chance of a causal comprehension for choreatic processes as well as for the mode of action of anticonvulsant and antispastic agents.     

The structural theory and the representational world: developmental and biological considerations

Although the intriguing question of whether the division into two viewpoints within the structural theory is a theoretical convenience or whether it mirrors fundamental psychobiological truths is not capable of full resolution at the moment, fortunately that resolution is not required for our usual clinical purposes. I believe that analytic work presents us with data readily conceptualized now from one, now from the other, viewpoint, so that analytic understanding benefits from the analyst's shifting his frame of reference from moment to moment in listening and associating to the patient's material. I believe that in every event within the analytic situation or in a person's life, our understanding is deepened and made more complete by approaching the phenomena from both vantage points, bearing in mind that the same ego we conceptualize as testing, assessing, and evaluating emergent drives is also assessing the congruence or discrepancy between the wished-for and perceived states of the representational world. These processes are occurring both in the analysand and in the analyst who is attempting to resonate with and understand the intrapsychic functioning of his patient. They constitute two observational vantage points within the structural theory, organizations of motives (Friedman, 1980) either of which may offer the most immediate access to understanding a particular segment of clinical material. I believe our understanding is most often deepened, however, by subsequent scrutiny in the light of the other model. I have tried here to supplement my previous exposition of a representational world point of view (J.G. Jacobson, 1983) by providing some of its developmental, ethological, and psychophysiological landmarks and underpinnings.     

Factor semantics forn-valued logics

In this note we prove that some familiar systems of finitely many-valued logics havefactor semantics, and establish necessary conditions for a system of many-valued logic having semantics of this kind.     

Two logit models for external analysis of preferences

A logit vector model and a logit ideal point model are presented for external analysis of paired comparison preference judgments aggregated over a homogeneous group. The logit vector model is hierarchically nested within the logit ideal point model so that statistical tests are available to distinguish between these two models. Generalized least squares estimation procedures are developed to account for heteroscedastic sampling error variances and specification error variances. Two numerical illustrations deal with judgments concerning employee compensation plans and preferences for salt and sugar in the brine of canned green beans.     

The logic of causal methods in social science

Two kinds of causal inference rules which are widely used by social scientists are investigated. Two conceptions of causation also widely used are explicated — the INUS and probabilistic conceptions of causation. It is shown that the causal inference rules which link correlation, a kind of partial correlation, and a conception of causation areinvalid. It is concluded anew methodology is required for causal inference.     

Social intimacy: An important moderator of stressful life events

Two studies were conducted to explore the role of social intimacy in predicting the individual's response to stress. In the first study the experimenter reinforced the experimental subjects' verbalizations during an interview on a fixed schedule for the first 3 minutes, withdrawing reinforcement for the final 4 minutes. The control group received reinforcement on a fixed schedule for the total 7 minutes. Subjects scoring low on a measure of intimacy disclosed less personal material during the withdrawal period in the experimental condition than in the control condition in contrast to high scoring subjects who maintained their level of disclosure for both parts of the interview. In the second study, previously experienced life change events were assessed. Individuals lacking a current intimacy were found to be prone to higher levels of emotional disturbance especially when many previous negative or few positive life change events had occurred.