The critical distance of interaction in the Zöllner illusion

Two experiments attempted to de termine the distance (as visual angle) over which the Zöllner distortion of a straight line could be produced by a background field. Experiment 1 showed that the background lines did not need to intersect the test line in order to distort it but could exert this effect up to a distance of 1 deg visual angle from it. Experiment 2 indicated that when the background lines do intersect the test line portions of these formed beyond an angle of 1 deg do not contribute to the distortion. These values may indicate the size of the cortical receptive fields interacting to produce the illusion.     

Effects of initial limb position on the accuracy, reaction time and electromyographic patterns of rapid movements

An experiment was performed to determine the effects of initial limb condition on final accuracy of rapid, elbow flexion movements in the horizontal plane. Electromyographic (EMG) recordings were also taken from an agonist (biceps) and antagonist (triceps) muscle by means of bipolar surface electrodes. In the experiment the subject's forearm was passively oscillated by means of an electric motor, and when an auditory buzzer sounded, the subject was required to react as quickly as possible and rapidly move to the previously learned target angle. Thus, movements could be initiated from either static or moving starting positions. The results indicated that general accuracy was not greatly affected by these manipulations, however, constant error and pre-motor reaction time suggested that subjects may have been utilizing initial limb condition information contrary to a mass-spring view. EMG data showed that the timing characteristics of the agonist and antagonist muscles were modulated, depending on the type of movement produced, supporting an impulse-timing model (Wallace 1981).     

Examination of ambiguous stimulus preferences with duration-based measures

Items that produced ambiguous results in an approach-based preference assessment were reassessed using a duration-based assessment. The reinforcing effects of three items on free-operant responding were subsequently tested. The results suggested that the duration-based assessment produced slightly more differentiated results and that predictions about reinforcer value, based on this assessment, were accurate.     

Effects of movement duration and visual feedback on visual and proprioceptive components of prism adaptation

While looking through laterally displacing prisms, subjects pointed sagittally 80 times at an objectively straight-ahead target, completing a reciprocal out-and-back pointing movement ever 1, 3, or 6 s. Visual feedback was available early in the pointing movement or only late at the end of the movement. Aftereffect measures of adaptive shift (obtained after every 10 pointing trials) showed adaptive change only in limb position sense (i.e., proprioceptive adaptation) when movement duration was 1 s, regardless of visual feedback condition; but as movement duration increased, adaptive change in the eye position sense (i.e., visual adaptation) increased while proprioceptive adaptation decreased, especially for the late visual feedback condition. Regardless of visual feedback condition, proprioceptive adaptation showed the maximal rate of growth with the 1-s movement duration, whereas visual adaptation showed maximal growth with the 6-s movement duration. These results provide additional support for a model of adaptive spatial mapping in which the direction of strategically flexible coordination (guidance) between eye and limb (and consequently the locus of adaptive spatial mapping) is jointly determined by movement duration and timing of visual feedback. An additional effect of movement duration is to determine the rate of discordant inputs. Maximal growth of adaptation occurs when the input rate matches the response time of the spatial mapping function.     

Duhem and Koyré on Domingo de Soto

Galileo's view of science is indebted to the teaching of the Jesuit professors at the Collegio Romano, but Galileo's concept of mathematical physics also corresponds to that of Giovan Battista Benedetti. Lacking documentary evidence that would connect Benedetti directly with the Jesuits, or the Jesuits with Benedetti, I infer a common source: the Spanish connection, that is, Domingo de Soto. I then give indications that the fourteenth-century work at Oxford and Paris on calculationes was transmitted via Spain and Portugal to Rome and other centers where Jesuits had colleges, and figured in the rise of mathematical physics at the beginning of the seventeenth century. A result of these researches is their vindication of Duhem, as contrasted with Koyré, on the origins of modern mechanics.     

Handedness as a function of sex and age in a large population of Lemur

A population of 194 lemurs (Lemur spp.), 116 males and 78 females, from 1 to 30 years of age, was assessed for lateralized hand use in simple food reaching with a minimum of 100 reaches per animal. A hand preference was present in 80% of the population with a bias for use of the left hand that was most characteristic of male lemurs and young lemurs. The results confirm the presence of lateralization in prosimians, and we interpret the sex and age differences in relation to current theories of neural lateralization.     

Prospective investigation of postpartum depression: factors involved in onset and recovery

We examined the role of a number of psychosocial variables in the onset of postpartum depression and in recovery from depression that occurs during pregnancy. Women (N = 730) were recruited during pregnancy and were followed through 1 month postpartum. They were assessed on demographic variables and on measures of depressive symptomatology and diagnostic status, perceived stress, marital satisfaction, perceptions of their own parents, dysfunctional cognitions, and coping style. Onset of depression in the postpartum was predicted by the levels during pregnancy of depressive symptomatology and perceived maternal and paternal care during childhood. In contrast, recovery in the postpartum from depression during pregnancy was not predicted by the variables examined in this study. These results are discussed with reference to previous investigations that have examined depression that occurs outside the context of childbirth.