Holding an object one is looking at: Kinesthetic information on the object’s distance does not improve visual judgments of its size

Visual judgments of distance are often inaccurate. Nevertheless, information on distance must be procured if retinal image size is to be used to judge an object’s dimensions. In the present study, we examined whether kinesthetic information about an object’s distance—based on the posture of the arm and hand when holding it—influences the object’s perceived size. Subjects were presented with a computer simulation of a cube. This cube’s position was coupled to that of a rod in the subject’s hand. Its size was varied between presentations. Subjects had to judge whether the cube they saw was larger than, smaller than, or the same size as a reference. On some presentations, a small difference was introduced between the positions of the rod and of the simulated cube. When the simulated cube was slightly closer than the rod, subjects judged the cube to be larger. When it was farther away, they judged it to be smaller. We show that these changes in perceived size are due to alterations in the cube’s distance from the subject rather than to kinesthetic information.     

Fast Responses of the Human Hand to Changes in Target Position

If a target toward which an individual moves his hand suddenly moves, he adjusts the movement of his hand accordingly. Does he use visual information on the target's velocity to anticipate where he will reach the target? These questions were addressed in the present study. Subjects (N = 6 in each of 4 experiments) were instructed to hit a disk with a rod as soon as it appeared on a screen. Trajectories of the hand toward stationary disks were compared with those toward disks that jumped leftward or rightward as soon as the subject's hand started moving toward the screen, and with those in which either the disk or the background started moving leftward or rightward. About 110 ms after the disk was suddenly displaced, the moving hand was diverted in the direction of the perturbation. When the background moved, the disk's perceived position shifted in the direction in which the background was moving, but the disk appeared to be moving in the opposite direction. When hitting such disks, subjects adjusted their movement in accordance with the perceived position, rather than moving their hand in the direction of the perceived motion in anticipation of the disk's future displacement. Thus, subjects did not use the perceived velocity to anticipate where they would reach the target but responded only to the change in position     

Simultaneous processing of visual information and planning of hand movements in a visuo-manual search task

When searching for a target with eye movements, saccades are planned and initiated while the visual information is still being processed. If hand movements are needed to perform a search task, can they too be planned while visual information from the current position is still being processed? To find out we studied a visual search task in which participants had to move their hand to shift a window through which they could see the items. The task was to find an O in a circle of Cs. The size of the window and the sizes of the gaps in the Cs were varied. Participants made fast, smooth arm movements between items and adjusted their movements, when on the items, to the window size. On many trials the window passed the target and returned, indicating that the next movement had been planned before identifying the item that was in view.     

The use of proprioception and tactile information in haptic search

To investigate how tactile and proprioceptive information are used in haptic object discrimination we conducted a haptic search task in which participants had to search for either a cylinder, a bar or a rotated cube within a grid of aligned cubes. Tactile information from one finger is enough to detect a cylinder amongst the cubes. For detecting a bar or a rotated cube amongst cubes touch alone is not enough. For the rotated cube this is evident because its shape is identical to that of the non-targets, so proprioception must provide information about the orientation of the fingers and hand when touching it. For the bar one either needs proprioceptive information about the distance and direction of a single finger’s movements along the surfaces, or proprioceptive information from several fingers when they touch it simultaneously. When using only one finger, search times for the bar were much longer than those for the other two targets. When the whole hand or both hands were used the search times were similar for all shapes. Most errors were made when searching for the rotated cube, probably due to systematic posture-related biases in judging orientation on the basis of proprioception. The results suggest that tactile and proprioceptive information are readily combined for shape discrimination.     

Learning from Tolstoy: Forgetfulness and Recognition in Literary Edification

Philosophers have often applied a distinctively epistemic framework to the question of how moral knowledge can be derived from fictional literature, by considering how true propositions, or their argumentative support, can be the cognitive fruits of reading works of fiction. I offer an alternative approach. I focus not on whether readers fail to assent to the truth of a proposition or fail to provide it rational support. Instead, I focus on how readers fail to accord a truth (which they already accept) adequate importance in their web of beliefs about living a good human life. This is a form of ignorance, but in the form of neglect, or failure to pay proper regard – which is one sense of the term ‘forgetfulness’. I argue that works of fictional literature may, at times, stimulate audience members to overcome their own particular forms of forgetfulness in this respect. And I use Tolstoy’s The Death of Ivan Ilyich as a case in point.

Experimental pragmatics: a Gricean turn in the study of language

Discerning the meaning of an utterance requires not only mastering grammar and knowing the meanings of words but also understanding the communicative (i.e., pragmatic) features of language. Although it has been an ever present aspect of linguistic analyses and discussions, it is only over the last ten years or so that cognitive scientists have been investigating--in a concerted fashion--the pragmatic features of language experimentally. We begin by highlighting Paul Grice's contributions to ordinary language philosophy and show how it has led to this active area of experimental investigation. We then focus on two exemplary phenomena--'scalar inference' and 'reference resolution'--before considering other topics that fit into the paradigm known as 'experimental pragmatics'.     

The Palestinian/Israeli Conflict: A Geopolitical Identity Disorder

In this paper, the author considers that the large-group dynamics in certain war-torn, hot spots throughout the world are symptoms of a “geopolitical identity disorder.” He extrapolates from the model of the severely traumatized psyche in dissociative identity disorder in which there is so much intolerable emotion, destructive aggression and conflict that different selves with different identities develop which are unable to recognize how interdependent and related they actually are. In the most extreme cases, one dissociated self tries to kill off “the other” in order to gain exclusive control of the body and make it comply with his or her wishes and vision. In actuality, however, such an attempt is a dissociated suicide plan with lethal implications. This model is applied to the Palestinian/Israeli situation where there is a deadly battle over the land. A clinical vignette is offered to illustrate these ideas and offer possibilities for help.     

Rorschach Comprehensive System data for a sample of 52 older adult nonpatients from the United States

This study is composed of 52 older adults, ages 60 to 80, all from the United States. In addition to being administered the Rorschach (Rorschach, 1942), all participants also were administered the Wechsler Adult Intelligence Scale-Revised (WAIS-R; Weschler, 1981), the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989), the Neuro Cognitive Status Examination (NCSE; Kiernan, Mueller, Langston, & Van Dyke, 1987), and the Trail Making Test Part B (Reitan, 1958; Reitan & Wolfson, 1993). Examiners included the principal author as well as three other trained examiners. Inclusion criteria are described. Interrater reliability statistics at the response level are presented along with scores for the Rorschach Comprehensive System (CS; Exner, 1995).     

Temporal integration of monocular images separated in time: stereopsis, stereoacuity, and binocular luster

We evaluated stereopsis and binocular luster using electronically controlled shutter glasses with alternating monocular stimulation. In Experiment 1, we used the standard method for testing stereoacuity to obtain a gradual measure of stereopsis. Stereo thresholds decreased with increasing alternating frequency of two monocular half-images without a delay between them. Increasing delays led to increasing thresholds. In Experiment 2, we compared stereopsis resulting from two monocular half-images of a random-dot stereogram and binocular luster with respect to the minimum alternating frequency of the two half-images and the maximum interocular delay that were tolerated without a breakdown of the impression. Below 3 Hz, no stereopsis occurred. Binocular luster was observed only above 10 Hz. The mean threshold of interocular delay for detecting the global figure in a random-dot stereogram was about 51 msec, but for binocular luster it was about 20 msec. Overall, temporal integration was better for stereopsis than for binocular luster.     

Effects of texture and shape on perceived time to passage: knowing "what" influences judging "when"

In the present study, we examined whether it is easier to judge when an object will pass one's head if the object's surface is textured. There are three reasons to suspect that this might be so: First, the additional (local) optic flow may help one judge the rate of expansion and the angular velocity more reliably. Second, local deformations related to the change in angle between the object and the observer could help track the object's position along its path. Third, more reliable judgments of the object's shape could help separate global expansioncaused by changes in distance from expansion due to changes in the angle between the object and the observer. We can distinguish among these three reasons by comparing performance for textured and uniform spheres and disks. Moving objects were displayed for 0.5-0.7 sec. Subjects had to decide whether the object would pass them before or after a beep that was presented 1 sec after the object started moving. Subjects were not more precise with textured objects. When the disk rotated in order to compensate for the orientation-related contraction that its image would otherwise undergo during its motion, it appeared to arrive later, despite the fact that this strategy increases the global rate of expansion. We argue that this is because the expected deformation of the object's image during its motion is considered when time to passage is judged. Therefore, the most important role for texture in everyday judgments of time to passage is probably that it helps one judge the object's shape and thereby estimate how its image will deform as it moves.