Similarity between hypotheses and evidence

We explore two novel consequences of similarity-based likelihood judgment. In Section I, we distinguish between the evidence on which judgments are based and the hypotheses that serve as the objects of judgment. The location of a feature, whether in the evidence or the hypotheses, influences the perceived similarity between evidence and hypotheses and consequently yields judgments that are inconsistent with the requirements of probability theory. In Section II, we examine judgment of disjunctive hypotheses. For certain types of disjunctions, the assessment of similarity produces consistent nonmonotonicities: the support of a disjunction is smaller than that of one of its components. Finally, we discuss the implications of our findings in terms of support theory and the principle of context independence.     

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     

Terrorists and Democrats: Individual Reactions to International Attacks

Three experiments conducted in 1997 and 1998 explored individual responses to reported fictitious international conflict involving the United States and other nations. Participants escalated the conflictual level of their responses to repeated attacks. In Experiment 1, escalation of conflict was greater in response to terrorist attacks than to military ones. In Experiment 2, after the initial attacks, men were more conflictual in responding to terrorist attacks by a democratic nation than by a nondemocratic nation, whereas the opposite pattern was found for women. In Experiment 3, participants responded with a higher level of conflict to terrorist attacks on military targets than to attacks on cultural/educational targets. Participants with greater personality dominance showed steeper escalation of conflict in their responses across successive attacks. These results are interpreted within the framework of an image theory of international relations and an expansion of the democratic peace hypothesis.     

Moderate Aerobic Exercise, T'ai Chi, and Social Problem-Solving Ability in Relation to Psychological Stress

This study evaluated the importance of exercise mode, social problem-solving ability, gender, and age in relation to anxiety and perceived daily hassles. Adult participants were classified as moderate aerobic exercisers, T'ai Chi exercisers, or sedentary via completion of a questionnaire. Social problem-solving ability, state and trait anxiety, and frequency and severity of daily hassles were measured. As predicted, scores indicating effective social problem-solving ability were associated with fewer reported severe daily hassles and with lower scores on state and trait anxiety. For state and trait anxiety, a main effect of exercise mode emerged after age and gender were controlled. A 3-way interaction involving age, gender, and exercise mode suggested that age and gender moderate the effects of exercise on anxiety, that is, the stress-reducing efficacy of different exercise modes may be dependent on a person's age and/or gender. Implications for theory, research, and practice are discussed.     

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.     

Global inhibition and midcourse corrections in speeded aiming

When some perceptual-motor relationships are reversed, participants might adopt a global inhibition strategy that replaces all normal movements with reversed movements. In two experiments, participants practiced moving a cursor from a start position to target locations. In a perceptual-motor reversal condition, in which horizontal but not vertical movements were reversed, participants were trained to move only to certain locations. Testing involved moving to all locations under the same reversal condition. Training on a subset of locations yielded partial transfer to untrained locations. These results support a global inhibition hypothesis modified to include both midcourse corrective movements and training specificity.     

A mental practice superiority effect: less retroactive interference and more transfer than physical practice

Two experiments explored the benefits to retention and transfer conferred by mental practice. During familiarization, participants typed 4-digit numbers and took an immediate typing test on both old and new numbers. Participants then typed old 4-digit numbers, either physically or mentally, with either a different response configuration or the opposite hand from that used during familiarization. On a delayed test, participants physically typed both old and new numbers with the same response configuration and hand used during familiarization. Mental practice led to less retroactive interference and more transfer than did physical practice, supporting the hypothesis that mental practice strengthens an abstract representation that does not involve specific effectors.     

Cognitive complications moderate the speed‐accuracy tradeoff in data entry: a cognitive antidote to inhibition

Three experiments explored a speed‐accuracy tradeoff reflecting decreasing response times (RTs) and increasing errors across trials in a data entry task. In Experiment 1, cognitive and motoric stressors were independently added to data entry, with the combination of stressors yielding the greatest decline in accuracy across blocks. Experiment 2 compared mental multiplication and simple data entry and manipulated the provision of feedback. Accuracy improved with both mental multiplication and feedback. Experiment 3 varied only the concluding keystroke; this extra requirement led to overall improvements in accuracy. In each experiment, RTs improved across trials. These results suggest that cognitive complications can serve as antidotes to inhibitory effects and can overcome the decline in accuracy due to continuous work on data entry. Copyright © 2007 John Wiley & Sons, Ltd.