Bouncing a ball: Tuning into dynamic stability.

Rhythmically bouncing a ball with a racket was investigated and modeled with a nonlinear map. Model analyses provided a variable defining a dynamically stable solution that obviates computationally expensive corrections. Three experiments evaluated whether dynamic stability is optimized and what perceptual support is necessary for stable behavior. Two hypotheses were tested: (a) Performance is stable if racket acceleration is negative at impact, and (b) variability is lowest at an impact acceleration between -4 and -1 m/s2. In Experiment 1 participants performed the task, eyes open or closed, bouncing a ball confined to a 1-dimensional trajectory. Experiment 2 eliminated constraints on racket and ball trajectory. Experiment 3 excluded visual or haptic information. Movements were performed with negative racket accelerations in the range of highest stability. Performance with eyes closed was more variable, leaving acceleration unaffected. With haptic information, performance was more stable than with visual information alone. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Movement prediction and movement production.

The prediction of future positions of moving objects occurs in cases of actively produced and passively observed movement. Additionally, the moving object may or may not be tracked with the eyes. The authors studied the difference between active and passive movement prediction by asking observers to estimate displacements of an occluded moving target, where the movement was driven by the observer's manual action or was passively observed. In the absence of eye tracking, they found that in the active condition, estimates are more anticipatory than in the passive conditions. Decreasing the congruence between motor action and visual feedback diminished but did not eliminate the anticipatory effect of action. When the target was tracked with the eyes, the effect of manual action disappeared. Results indicate distinct contributions of hand and eye movement signals to the prediction of trajectories of moving objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants interpret ambiguous requests for absent objects.

The current studies investigated 2 skills involved in 14- to 20- month-olds' ability to interpret ambiguous requests for absent objects: tracking others' experiences (Study 1) and representing links between speakers and object features across present and absent reference episodes (Study 2). In the basic task, 2 experimenters played separately with a different ball. The balls were placed in opaque containers. One experimenter asked infants to retrieve her ball using an ambiguous request ("Where's the ball?"). In Study 1, infants used the experimenter's prior verbal and physical contact with the ball to interpret the request. A control condition demonstrated that infants were interpreting the request and not responding to the mere presence of the experimenter. Study 2 revealed that only infants who were given stable cues to the ball's spatial location appropriately interpreted the request: When spatial information was put in conflict with a color cue, infants did not select the correct ball. Links to infants' spatial memory skills and emerging pragmatic understanding are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impact of a group decision on perception of one's own and others' attitudes.

We designed two experiments to examine the influence of a group decision on subjects' estimates of the attitudes of group members. In Experiment 1, subjects were led to believe that their initial vote in a jury decision-making task either agreed or disagreed with the majority vote and, independently of agreement with the majority, that their vote either agreed or disagreed with the final group decision. Subjects' own attitudes changed in the direction of the majority position only when the group decision was inconsistent with their initial vote. Consistent with prior research on the group attribution error, subjects inferred a correspondence between the final group decision and the other jurors' attitudes about the guilt or innocence of the defendant. In Experiment 2, subjects actively participated in or passively observed a group decision that either had or did not have direct consequences for the voting group. We found evidence of the group attribution error in both active participants' and passive observers' inferences about the attitudes of group members. Moreover, subjects tended to infer correspondence between the decision and the attitudes of voting members only when the decision had no immediate consequences for the group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perception of speed in an automobile: Estimation and production.

In 2 experiments, the authors studied the perception of speed in an automobile as a function of speed, previous acceleration, trajectory, driving experience, and sex of the participants. Three levels of driving experience were observed: nondrivers, new drivers, and experienced drivers. In Experiment 1, 60 participants verbally estimated the speed at which they traveled by car. In Experiment 2, 30 participants performed an active estimation task with an accelerator to produce a target speed, in addition to the same passive verbal estimation. The results showed a tendency to underestimate speed, and this effect was more pronounced at lower speeds. The predicted overcompensation in the active production task confirmed the general equivalence of both passive and active estimation despite certain differences. Results are discussed from a psychophysical viewpoint, and implications for driving behavior are also considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of instructional set on attributions of nonvolition during hypnotic and nonhypnotic analgesia.

Fifty highly hypnotizable subjects were assigned to four treatment groups or a no-treatment control group and then underwent two pain stimulation trials. Half the treated subjects were administered hypnotic analgesia, half waking analgesia. Within hypnotic and nonhypnotic treatments, half the subjects were given actively worded analgesia instructions, half passively worded instructions. Subjects in the four treated groups reported equivalent pain reduction and equivalent use of coping imagery, although hypnotic subjects rated themselves as more deeply hypnotized than did nonhypnotized subjects. Both hypnotic and nonhypnotic subjects given passive instructions rated their pain reduction as occurring involuntarily, whereas those given active instructions reported that their pain was reduced through their active use of coping strategies. These findings support sociocognitive formulations of hypnotic responding that view ratings of involuntariness as reflecting contextually guided interpretations of behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shedding some light on catching in the dark: Perceptual mechanisms for catching fly balls.

To catch a lofted ball, a catcher must pick up information that guides locomotion to where the ball will land. The acceleration of tangent of the elevation angle of the ball (AT) has received empirical support as a possible source of this information. Little, however, has been said about how the information is detected. Do catchers fixate on a stationary point, or do they track the ball with their gaze? Experiment 1 revealed that catchers use eye and head movements to track the ball. This means that if AT is picked up retinally, it must be done by means of background motion. Alternatively, AT could be picked up by extraretinal mechanisms, such as the vestibular and proprioceptive systems. In Experiment 2, catchers reliably ran to intercept luminous fly balls in the dark, that is, in absence of a visual background, under both binocular and monocular viewing conditions. This indicates that the optical information is not detected by a retinal mechanism alone. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two-year-olds' search strategies and visual tracking in a hidden displacement task.

Children younger than 3 years have difficulty with search tasks that involve hidden displacement. Partial visual information was provided about a ball's path as it moved toward a hiding place. Children (2.0 and 2.5 years old) saw a ball rolling down a ramp placed behind a transparent screen with 4 opaque doors. A wall, placed on the ramp and directly behind 1 of the doors, protruded above the screen and stopped the ball. Children were asked to find the ball. The transparency of the screen permitted visual tracking of the ball between the doors, but its final resting place was obscured. Both age groups were equally proficient at tracking the ball as it rolled behind the screen, but the 2.5-year-olds were more likely to reach to the correct door. Looking behavior was related to errors in the younger group in that tracking that stopped short or continued past the correct door was associated with incorrect choices. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceiving and tracking kinesthetic stimuli: Further evidence of motor–perceptual interactions.

Two experiments pursued previous studies (P. Viviani & P. Mounoud, 1990; P. Viviani & N. Stucchi, 1989) on motor–perceptual interactions. The right arm of blindfolded participants was moved passively along elliptic trajectories. Kinematics was either coherent or at variance with the relation (two-thirds power law) observed in active movements. In Experiment 1 participants compared the horizontal and vertical extent of the ellipses. Kinematics affected aspect ratio discrimination: The direction along which the movement decelerated was subjectively stretched. In Experiment 2 participants used the left arm to reproduce in real time the movement of the right arm. The trajectories of the left arm presented a stretch similar to the perceptual illusion demonstrated in Experiment 1. Between-arm asynchrony suggests that the motor control system cannot use kinesthetic information that is at variance with the flow of reafferences normally associated with voluntary movements. It is argued that these interactions occur at the level of a central amodal representation of the stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual factors in hitting and catching

To hit or catch an approaching ball, it is necessary to move a bat or hand to the right place at the right time. The performance of top sports players is remarkable: positional errors of less than 5 cm and temporal errors of less than 2 or 3 ms are reliably maintained. There are three schools of thought about how this is achieved. One holds that predictive visual information about where the ball will be at some future instance (when) is used to achieve the hit or catch. The second holds that the bat or hand is moved to the correct position by exploiting some relation between visual information and the required movement. The third focuses on the use of prior knowledge to supplement inadequate visual information. For a rigid spherical ball travelling at constant speed along or close to the line of sight, the retinal images contain both binocular and monocular correlates of the ball's instantaneous direction of motion in depth. Also, the retinal images contain both binocular and monocular information about time of arrival. Humans can unconfound and use this visual information, but they are unable to estimate the absolute distance of the ball or its approach speed other than crudely. In cricket, this visual inadequacy allows a slow bowler to cause the batsman to misjudge where the ball will hit the ground. Such a bowler uses a three-pronged strategy: first, to deliver the ball in such a way as to prevent the batsman from obtaining the necessary visual information until it is too late to react; secondly, to force the batsman to rely entirely on inadequate retinal image information; thirdly, to allow the batsman to learn a particular relationship between the early part of the ball's flight and the point where the ball hits the ground, and then to change the relationship with such skill that the batsman does not detect the change.     

Representational momentum for a spiral path.

When a ball is shot through a spiral tube at high speed, the ball emerges in a straight path tangent to the ball's point of departure from the tube. However, past research has shown that many Ss believe the ball follows a curved pathway. In the 3 experiments described in this article, a ball traveling through a spiral tube was animated on a computer graphics screen. Ss' memory distortions for positions of the ball along each of 3 pathways were measured using a representational momentum paradigm. Retention interval was varied across the 3 experiments. The results from the 3 experiments reported here replicate retention interval results previously reported for representational momentum effects, and they suggest that the representational pathway of a ball exiting a spiral tube is spiral in shape. These findings may shed some light on why people have demonstrated naiveté on the spiral tube problem in past research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eight-and-a-half-month-old infants' reasoning about containment events

The present research examined whether 8.5-month-old infants take into account the width and compressibility of an object when determining whether it can be inserted into a container. The infants in Experiment 1 saw 2 test events. At the start of each event, a tall container rested on the apparatus floor. Next, the container was hidden by a screen, and a large ball attached to the lower end of a rod was introduced into the apparatus and lowered behind the screen into the container. Finally, the screen was removed to reveal the ball's rod protruding above the container's rim. The only difference between the 2 test events had to do with the width of the containers: in 1 event (large-container event), the container was slightly wider than the ball; in the other event (small-container event), the container was only half as wide as the ball, so that it should have been impossible for the ball to be lowered into it. Infants in a control condition saw identical test events except that a small ball was used that could fit into either the large or the small container. The infants in the experimental condition looked reliably longer at the small- than at the large-container event, whereas those in the control condition tended to look equally at the 2 events. These results suggested that, although the infants never saw the ball and the container simultaneously, they realized that the large ball could fit into the large but not the small container, whereas the small ball could fit into both containers. In Experiment 2, the large ball used in Experiment 1 was replaced with an equally large but compressible ball. The results were negative, suggesting that the infants understood that the large compressible ball could be inserted into either the small or the large container. Finally, Experiment 3 confirmed the results of the experimental condition in Experiment 1, with a slightly different procedure. Together, the present results indicate that, by 8.5 months of age, infants are already capable of sophisticated reasoning about containment events.     

Manipulating and recognizing virtual objects: Where the action is.

In an earlier report (K. L. Harman, G. K. Humphrey, and M. A. Goodale, 1999), the authors demonstrated that Os who actively rotated 3-dimensional (3-D) novel objects on a computer screen later showed faster visual recognition of these objects than did Os who had passively viewed exactly the same sequence of images of these virtual objects. In Exp 1 of the present study, using 24 18–30 yr olds, the authors show that compared to passive viewing, active exploration of 3-D object structure led to faster performance on a "mental rotation" task involving the studied objects. They also examined how much time Os concentrated on particular views during active exploration. As found in the previous report, Os spent most of their time looking at the "side" and "front" views ("plan" views) of the objects, rather than the 3-quarter or intermediate views. This preference for the plan views of an object led to the examination of the possibility in Exp 2 that restricting the studied views in active exploration to either the plan views or the intermediate views would result in differential learning. 24 18–28 yr olds were used in Exp 2. It was found that recognition of objects was faster after active exploration limited to plan views than after active exploration of intermediate views. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relevance of action in perceiving affordances: Perception of catchableness of fly balls.

The catchableness of a fly ball depends on whether the catcher can get to the ball in time; accurate judgments of catchableness must reflect both spatial and temporal aspects. Two experiments examined the perception of catchableness under conditions of restricted information pickup. Experiment 1 compared perceptual judgments with actual catching and revealed that stationary observers are poor perceivers of catchableness, as would be expected by the lack of information about running capabilities. In Experiment 2, participants saw the 1st part of ball trajectories before their vision was occluded. In 1 condition, they started to run (as if to catch the ball) before occlusion; in another, they remained stationary. Moving judgments were better than stationary judgments. This supports the idea that perceiving affordances that depend on kinematic, rather than merely geometric, body characteristics may require the relevant action to be performed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Practise strengthens haptic capture.

When do haptic estimates of discordant visual-haptic size capture vision? Observers looked at a square through a minifying lens (50%) whilst they simultaneously touched the square from below through a hand-concealing cloth. Their subsequent match of the square’s size, rendered by touching a set of comparison squares, was haptically biased when they practised estimating the square’s size (Experiment 1, N = 72), when they actively explored rather than passively touched the square (Experiment 2, N = 24), but not when they were uninformed before inspecting the square that they would estimate its size (Experiment 3, N = 36). Evidently, the haptic exploratory strategies occasioned by the practise influenced the integration of the felt size and the seen size by weighing the haptic input more than the visual input, and this weight shifting manifested itself by strengthening haptic capture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mind over matter: Perceived success at psychokinesis.

Four experiments with 212 undergraduates showed that Ss' estimates of success on a psychokinetic (PK) task were independent of actual performance. In Exp I, Ss given a positive introductory set or no set about PK evidenced more illusory control than Ss given a negative set. In Exp II, both degree of general belief in psychic phenomena and the number of practice trials that Ss received influenced performance estimates, with high believers who received 10 practice trials providing the highest estimates and low believers who received 1 practice trial the lowest. In Exp III, Ss actively involved with the PK task judged their performance more positively than passively involved Ss. Exp IV showed that when they were actively involved in the task, Ss with an internal locus of control (Rotter's Internal–External Locus of Control Scale) gave higher estimates of their success than Ss with an external locus of control. When passively involved, internals and externals did not reliably differ in their estimates, but their estimates were lower in those of active/internals. Results support E. J. Langer's illusion-of-control theory and highlight the importance of general psychic belief and locus-of-control orientation in affecting perceived success at a psychic task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Running-wheel avoidance learning in rats (Rattus norvegicus): Effects of contingencies and comparisons of different strains.

In Experiment 1, we showed that active- and passive-avoidance responding in a running wheel was learned because of the avoidance contingency. In Experiment 2, strain differences among four commercially bred rats were assessed in an active-avoidance paradigm. Wistar, Donryu, and Fischer rats learned faster than Sprague-Dawleys. In Experiment 3, learning in a multiple active/passive avoidance schedule was examined, and both components of this task were learned. This multiple schedule was used to investigate strain differences in selectively bred rats in Experiments 4 and 5. Tsukuba low-emotional (TLE) rats responded more than Tsukuba high-emotional (THE) rats in both components. However, discrimination of passive components was better in THE than in TLE rats. Syracuse high-avoidance rats were superior in the active component, whereas Syracuse low-avoidance rats showed superior performance in the passive component. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in 4-year-old children's acquisition of vocabulary during storybook reading.

Two experiments were conducted to assess how children who differ in vocabulary knowledge learn new vocabulary incidentally from listening to stories read aloud. In both experiments, 4-yr-old children were classified as having either high or low word knowledge on the basis of a median split of their Peabody Picture Vocabulary Test—Revised (PPVT—R) standard scores. In Exp 1, children either listened passively or labeled pictures using novel words during the book readings. We found that children with larger vocabularies produced more novel words than did children with smaller vocabularies, and children who answered questions during the book readings comprehended and produced more words than did children who passively listened to the story. In Exp 2, children either listened to readings of a book, pointed to pictures during the readings, or labeled pictures during the readings. Children with larger vocabularies comprehended more novel words than did children with smaller vocabularies. Children who actively participated by labeling or pointing learned more words than did children who listened passively to book readings. Findings clarify the role of active responding by demonstrating that verbal and nonverbal responding are effective means of enhancing vocabulary acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On cognitive busyness: When person perceivers meet persons perceived.

Person perception includes three sequential processes: categorization (what is the actor doing?), characterization (what trait does the action imply?), and correction (what situational constraints may have caused the action?). We argue that correction is less automatic (i.e., more easily disrupted) than either categorization or characterization. In Experiment 1, subjects observed a target behave anxiously in an anxiety-provoking situation. In Experiment 2, subjects listened to a target read a political speech that he had been constrained to write. In both experiments, control subjects used information about situational constraints when drawing inferences about the target, but cognitively busy subjects (who performed an additional cognitive task during encoding) did not. The results (a) suggest that person perception is a combination of lower and higher order processes that differ in their susceptibility to disruption and (b) highlight the fundamental differences between active and passive perceivers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Specificity of practice in a ball interception task.

Learning of an aiming task has been shown to be specific to the sources of afferent information available during practice. However, this has not been the case when a one-hand ball-catching task has been used. The goal of the present study was to determine the cause of these conflicting results. 16 undergraduates practiced an interception task in either a normal vision condition or a ball-only condition. They were all then transferred to the ball-only condition, using either the same ball trajectories as in acquisition or different ones. Being transferred from a normal vision condition to a ball-only condition resulted in a significant increase in spatial interception errors, thus supporting the specificity of practice hypothesis. Using new ball trajectories in transfer caused a significant increase in error for all participants. The pattern of errors observed when new ball trajectories were used suggests that participants had difficulty correlating information about the location of their arm via proprioception and a combination of retinal and extra-retinal information about the ball trajectory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)