Apparent movement and change in perceived location of a simulus produced by a change in accommodative vergence

Using a psychophysical method of adjustment, 175 Ss, ranging in age from 3 to 20 years, made four adjustments each of a luminous line to subjective vertical, horizontal, and 45-deg tilts in the dark. There were no significant differences in mean errors of adjustment to the vertical and horizontal over the ages tested. There were significant differences in intra-S variability of adjustment to the horizontal and vertical, with the greatest improvement occurring before age 10. Older children and adults produced significantly larger mean errors of adjustment to the 45-deg tilt than did the younger children; but the variability of settings by younger children was very high, indicating that they did not discriminate the 45-deg tilt more accurately than the older groups. The intra-S variability at all ages showed that adjustment was more accurate to the horizontal and vertical than to the 45-deg tilt.     

Cognitive Load and Prism Adaptation

Subjects wore goggles with prisms that laterally displaced the visual field (rightward by 11.4°) and with full view of the limb engaged in paced (2-s rate) sagittal pointing at either an implicit (“straight ahead of the nose”) target (Experiment 1) or an explicit (positioned leftward by 11.4°) target (in Experiment 2). In experimental conditions, subjects performed a secondary cognitive task (mental arithmetic) simultaneously during target pointing. In control conditions, no cognitive load was imposed. Aftereffect measures of adaptation to the prismatic displacement were not substantially different when problem solving was required, but terminal error of the exposure pointing task was reliably affected by cognitive load. These results are consistent with the hypothesis of separable mechanisms for adaptive coordination and adaptive alignment. Adaptive coordination may be mediated by strategically flexible coordinative linkage between sensory–motor systems (eye–head and hand—head), but spatial alignment seems to be mediated by adaptive encoders within coordinatively linked subsystems. If the coordination task involves predominately automatic processing, coordinative linkage can be frequent enough under cognitive load for substantial realignment to occur even though exposure performance (adaptive coordination) may be less than optimal.     

Cognitive Load and Prism Adaptation

Subjects wore goggles with prisms that laterally displaced the visual field (rightward by 11.4 degree) and with full view of the limb engaged in paced (2-s rate) sagittal pointing at either an implicit ("straight ahead of the nose") target (Experiment 1) or an explicit (positioned leftward by 11.4 degree) target (in Experiment 2). In experimental conditions, subjects performed a secondary cognitive task (mental arithmetic) simultaneously during target pointing. In control conditions, no cognitive load was imposed. Aftereffect measures of adaptation to the prismatic displacement were not substantially different when problem solving was required, but terminal error of the exposure pointing task was reliably affected by cognitive load. These results are consistent with the hypothesis of separable mechanisms for adaptive coordination and adaptive alignment. Adaptive coordination may be mediated by strategically flexible coordinative linkage between sensory motor systems (eye-head and hand-head), but spatial alignment seems to be mediated by adaptive encoders within coordinatively linked subsystems. If the coordination task involves predominately automatic processing, coordinative linkage can be frequent enough under cognitive load for substantial realignment to occur even though exposure performance (adaptive coordination) may be less than optimal.     

Size-distance paradox with accommodative micropsia

Two experiments tested the hypothesis that the paradoxical relative distance judgment associated with the size-distance paradox is due to the visual system’s assuming equal linear size and perceiving a smaller angular size for the closer stimulus equal in visual angle. In Experiment I, two different sized coins were presented successively, and 16 Ss were asked to give ordinal judgments of apparent distance and apparent size. When the two coins depicted the same figures, the closer stimulus was judged to be farther and smaller, more frequently, than when two coins depicted different figures. In Experiment II, 48 Ss were asked to give ratio judgments of apparent distance, apparent linear size, and apparent angular size for two stimuli which were presented successively. When the stimuli were of equal shape, the mean ratios of the far stimulus to the near stimulus were smaller for the apparent distance but larger for the apparent linear size and angular size than when the stimuli were of different shape. The obtained distance judgments were consistent with the hypothesis but the obtained judgments of linear size and angular size were not.     

Prism adaptation while tracking and saccading

It is known that positional discordance between the spatial senses is a sufficient condition for prism adaptation of registered eye-in-head position. In this experiment adaptation was carried out under conditions in which Ss viewed their feet while making extensive tracking or saccading movements of their eyes. It has been claimed that tracking makes available less precise position information than saccading (Festinger and Canon 1965), but it is found that both modes are equally successful in causing this form of adaptation. It is concluded that either tracking and saccading yield equally valid estimates of eye-in-head position, or that the normal straight ahead position of the eye is a unique reference position.     

Prism adaptation in left-handers

Two experiments with left-handers examined the features of prism adaptation established by previous research with right-handers. Regardless of handedness, (1) rapid adaptation occurs in exposure pointing with developing error in the opposite direction after target achievement, especially with early visual feedback in target pointing; (2) proprioceptive or visual aftereffects are larger, depending on whether visual feedback is available early or late, respectively, in target pointing; (3) the sum of these aftereffects is equal to the total aftereffect for the eye-hand coordination loop; (4) intermanual transfer of visual aftereffects occurs only for the dominant hand; and (5) visual aftereffects are larger in left space when the dominant hand is exposed to leftward displacement. A notable handedness difference is that, while transfer of proprioceptive aftereffects only occurs to the nondominant hand in right-handers, transfer occurs in both directions for left-handers, but regardless of handedness, such transfer only occurs when the exposed hand is tested first after exposure. A discussion then focuses on the implications of these data for a theory of handedness.     

Prism adaptation in schizophrenia

The prism adaptation test examines procedural learning (PL) in which performance facilitation occurs with practice on tasks without the need for conscious awareness. Dynamic interactions between frontostriatal cortices, basal ganglia, and the cerebellum have been shown to play key roles in PL. Disruptions within these neural networks have also been implicated in schizophrenia, and such disruptions may manifest as impairment in prism adaptation test performance in schizophrenia patients. This study examined prism adaptation in a sample of patients diagnosed with schizophrenia (N=91) and healthy normal controls (N=58). Quantitative indices of performance during prism adaptation conditions with and without visual feedback were studied. Schizophrenia patients were significantly more impaired in adapting to prism distortion and demonstrated poorer quality of PL. Patients did not differ from healthy controls on aftereffects when the prisms were removed, but they had significantly greater difficulties in reorientation. Deficits in prism adaptation among schizophrenia patients may be due to abnormalities in motor programming arising from the disruptions within the neural networks that subserve PL.     

First-Trial Adaptation to Prism Exposure

Terminal target-pointing error on the 1st trial of exposure to optical displacement is usually less than that expected from the optical displacement magnitude. Such 1st trial adaptation was confirmed in 2 experiments (N = 48 students in each) comparing pointing toward optically displaced targets and toward equivalent physically displaced targets (no optical displacement), with visual feedback delayed until movement completion. First-trial performance could not be explained by ordinary target undershoot, online correction, or reverse optic flow information about true target position and was unrelated to realignment aftereffects. Such adaptation might be an artifact of the asymmetry of the structured visual field produced by optical displacement, which induces a felt head rotation opposite to the direction of the displacement, thereby reducing the effective optical displacement.     

Prism adaptation to dynamic events

In the present study, we explored adaptation to prism-displaced dynamic and static events under conditions of minimal information. Many of our interactions with the world are dynamic and involve reaching for or intercepting moving objects. The consequences (or feedback) of those interactions entail the presence or absence of physical contact with the moving objects. In this study, humans learned, with only heptic feedback, to intercept optically displaced falling balls. To eliminate visual feedback, the falling balls disappeared behind an occluder (which systematically varied in size across groups) prior to either striking or missing a subject's hand. As occluder size decreased, adaptation increased. With minimum occluder sizes, the greatest adaptation occurred around the training position, and adaptation decreased as distance between training and testing positions increased. The results can best be described in terms of a generalization gradient centered around the training position. This generalization gradient was not present when subjects were trained with ecologically similar static arrays. Implications for models of adaptation are discussed.     

Prism adaptation in alternately exposed hands

We assessed intermanual transfer of the proprioceptive realignment aftereffects of prism adaptation in right-handers by examining alternate target pointing with the two hands for 40 successive trials, 20 with each hand. Adaptation for the right hand was not different as a function of exposure sequence order or postexposure test order, in contrast with adaptation for the left hand. Adaptation was greater for the left hand when the right hand started the alternate pointing than when the sequence of target-pointing movements started with the left hand. Also, the largest left-hand adaptation appeared when that hand was tested first after exposure. Terminal error during exposure varied in cycles for the two hands, converging on zero when the right hand led, but no difference appeared between the two hands when the left hand led. These results suggest that transfer of proprioceptive realignment occurs from the right to the left hand during both exposure and postexposure testing. Such transfer reflects the process of maintaining spatial alignment between the two hands. Normally, the left hand appears to be calibrated with the right-hand spatial map, and when the two hands are misaligned, the left-hand spatial map is realigned with the right-hand spatial map.     

Empathic accuracy and accommodative behavior among newly married couples

An established method for assessing empathic accuracy was used to examine the consequences of accurate understanding during the early years of marriage. Structural equation modeling analyses simultaneously examined within–individual and across–partner associations among variables (actor effects and partner effects). During the first year of marriage, actor effects and partner effects were observed for two presumed consequences of empathic accuracy—accommodative behavior and couple well–being. Actor effects, partner effects, or both were observed for three possible determinants of empathic accuracy—commitment level, partner perspective–taking, and psychological femininity. Levels of empathic accuracy reliably declined following the first year of marriage, as did the strength of the above–noted associations with empathic accuracy.     

Prism aftereffects disrupt interlimb rhythmic coordination

The authors examined effects of prism-induced proprioceptive aftereffects on coordination of 95 participants and compared interlimb rhythmic coordination performed before versus after exposure to prisms of varying optical displacements. The observed steady states of relative phase for postprism exposure coordination were shifted by a small but significant amount, but not across all prism conditions. Phase-shift direction was not specific to the direction of optical displacement and was not, across all conditions, proportional to the magnitude of optical displacement. Prism exposure was associated with increased relative phase variability for all prism conditions. A no-prism control group showed no changes in interlimb rhythmic coordination. The results suggest that prism-induced proprioceptive aftereffects have general, disruptive effects on interlimb rhythmic coordination.     

Self-notions and top-down distortion

Abstract

John Perry offers an unusually substantive, and initially plausible, account of the conceptual role of first-person thought. This paper critiques Perry’s account, particularly in what it says about action explanation, and offers a partial alternative. It also identifies three high-level assumptions about what accounts of conceptual roles should look like that plausibly explain why Perry’s account goes off track in the ways that it does – this is the top-down distortion of the title. Identifying and arguing against the three assumptions helps point in the direction of a better account.     

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.