Attentional requirements for location and distance of movement: encoding and recognition

The purpose of this experiment was to study the early processing stages of encoding and recognition of slow movement in a short-term motor-memory paradigm. These stages were examined by determining whether Laabs' (1973) differential decay rates for location of movement and distance of movement could be replicated when the interfering activity was performed during the criterion and replication movements. 20 subjects performed a linear-positioning task in a 2 X 2 X 2 (count X movement type X retention interval) experimental design. 10 subjects in one condition counted backwards by 3s during the criterion and replication movements. There were no detrimental effects for location and distance-cue reproduction when attention was shared with counting backwards. Like Laabs' results, location of movement was maintained over the 15-sec. interval while distance of movement spontaneously changed. These results supported the notion that the early stages of encoding and recognition of cues for movement can occur unaffected by a secondary task.     

Changes in the relationship between movement velocity and movement distance in primary focal hand dystonia

The authors examined the relationship between movement velocity and distance and the associated muscle activation patterns in 18 individuals with focal hand dystonia (FHD) compared with a control group of 18 individuals with no known neuromuscular condition. Participants performed targeted voluntary wrist and elbow flexion movements as fast as possible across 5 movement distances. Individuals with FHD were slower than controls across all distances, and this difference was accentuated for longer movements. Muscle activation patterns were triphasic in the majority of individuals with FHD, and muscle activation scaled with distance in a similar manner to controls. Cocontraction did not explain movement slowing in individuals with dystonia, but there was a trend toward underactivation of the 1st agonist burst in the dystonic group. The authors concluded that slowness is a consistent feature of voluntary movement in FHD and is present even in the absence of dystonic posturing. Underactivation of the 1st agonist burst appears to be the most likely reason to explain slowing.     

North is up(hill): Route planning heuristics in real-world environments

Navigators use both external cues and internal heuristics to help them plan efficient routes through environments. In six experiments, we discover and seek the origin of a novel heuristic that causes participants to preferentially choose southern rather than northern routes during map-based route planning. Experiment 1 demonstrates that participants who are tasked to choose between two equal-length routes, one going generally north and one south, show reliable decision preferences toward the southern option. Experiment 2 demonstrates that participants produce a southern preference only when instructed to adopt egocentric rather than allocentric perspectives during route planning. In Experiments 3-5, we examined participants’ judgments of route characteristics and found that judgments of route length and preferences for upper relative to lower path options do not contribute to the southern route preference. Rather, the southern route preference appears to be a result of misperceptions of increased elevation to the north (i.e., north is up). Experiment 6 further supports this finding by demonstrating that participants provide greater time estimates for north- than for equivalent south-going routes when planning travel between U.S. cities. Results are discussed with regard to predicting wayfinding behavior, the mental simulation of action, and theories of spatial cognition and navigation.     

Fake hand in movement: Visual motion cues from the rubber hand are processed for kinesthesia

The feeling that a fake (e.g. rubber) hand belongs to a person's own body can be elicited by synchronously stroking the fake hand and the real hand, with the latter hidden from view. Here, we sought to determine whether visual motion signals from that incorporated rubber hand would provide relevant cues for sensing movement (i.e. kinesthesia). After 180 s of visuo-tactile synchronous or asynchronous stroking, the fake hand was moved along the lateral or the sagittal axis. After synchronous stroking, movement of the rubber hand induced illusory movement of the static (real) hand in the same direction; the illusion was slightly more frequent and more intense when the fake hand was moved along the sagittal axis. We therefore conclude that visual signals of motion originating from the rubber hand are integrated for kinesthesia by the central nervous system just as visual signals from the real hand are.     

Time does not flow without language: Spatial distance affects temporal duration regardless of movement or direction

Much evidence has suggested that people conceive of time as flowing directionally in transverse space (e.g., from left to right for English speakers). However, this phenomenon has never been tested in a fully nonlinguistic paradigm where neither stimuli nor task use linguistic labels, which raises the possibility that time is directional only when reading/writing direction has been evoked. In the present study, English-speaking participants viewed a video where an actor sang a note while gesturing and reproduced the duration of the sung note by pressing a button. Results showed that the perceived duration of the note was increased by a long-distance gesture, relative to a short-distance gesture. This effect was equally strong for gestures moving from left to right and from right to left and was not dependent on gestures depicting movement through space; a weaker version of the effect emerged with static gestures depicting spatial distance. Since both our gesture stimuli and temporal reproduction task were nonlinguistic, we conclude that the spatial representation of time is nondirectional: Movement contributes, but is not necessary, to the representation of temporal information in a transverse timeline.     

Times for transitions between hand and foot responses in a self-paced task

In a self-paced task subjects responded to each of four equally probable signals with a different one of their four limbs. Response times were examined as a function of the 16 possible transitions between limbs. Repeated responses were shown to be faster than any other transitions, while responses following responses with an ipsilateral limb were relatively slow. The implications of these results for models for the “repetition effect” are discussed.     

Memory for movement: Interaction of location and distance cues and imagery ability

The present experiments examined the role of imagery ability in recall of either the terminal location or the distance of a preselected horizontal linear movement following changes in the recall starting position. Subjects were selected on the basis of their scores on a shortened version of the Betts Questionnaire upon Mental Imagery (Betts Q.M.I., Sheehan 1967). Both high and low imagers were assigned to one of four groups, HIL, LIL, HID, LID, the last letter indicating the movement cue (terminal location or distance moved) to be recalled. Recall of the appropriate movement cue from one of four new recall starting positions occurred after either a 5-sec or 30-sec unfilled retention interval. Analysis of constant error indicated all groups were unable to recall the specified movement cue independent of the other source of information, even when subjects were given explicit instructions to utilise an imagery strategy. The data corroborate our earlier findings that memory for self paced movements is based on an interaction of location and distance cues derived from the criterion movement.     

Visual guidance for hand advance but not hand withdrawal in a reach-to-eat task in adult humans: reaching is a composite movement

Many animal species use reaching for food to place in the mouth (reach-to-eat) with a hand, and it may be a primitive movement. Although researchers (I. Q. Whishaw, 2005; A. N. Iwaniuk & I. Q. Whishaw, 2000; M. Gentiluci, I. Toni, S. Chieffi, & G. Pavesi, 1994) have described visual guidance of reaching in both normal and brain-injured human and nonhuman primates, researchers have not described the contribution of vision during advance of the limb to grasp food and during withdrawal of the limb with food to the mouth. To evaluate visual contributions, the authors monitored eye movements in young adults as they reached for food with and without vision. Participants visually engaged the target prior to the 1st hand movement and disengaged it as the food was grasped. Visual occlusion slowed limb advance and altered digit shaping but did not affect withdrawal. The dependence on visual control of advance but not withdrawal suggests that the reach-to-eat movement is a composite of 2 basic movements under visual and tactile/proprioceptive guidance, respectively.     

Sinistrals’ upper hand: Evidence for handedness differences in the representation of body space

A difference in the perception of extrapersonal space has been shown to exist between dextrals and sinistrals. On the classical line bisection task, this difference is evident in a greater left bias for dextrals compared to sinistrals. Different modalities and regions of space can be affected. However, it has not yet been investigated whether a systematic bias also exists for the perception of personal or body space. We investigated this by using three tasks which assess different aspects of personal space in an implicit and explicit way. These tasks were performed by strongly right-handed (dextrals), strongly left-handed (sinistrals) and mixed-handed participants. First, a task of pointing to three areas of one’s own body without the use of visual information showed dextrals to have an asymmetric estimation of their body. In right hemispace, dextrals’ pointing was at a greater distance from the midsagittal plane compared to pointing in left hemispace. No such asymmetry was present for sinistrals, while mixed-handers’ performance was intermediate to that of strong right- and strong left-handers. Second, a task of recovering circular patches from their body surface whilst blindfolded also showed superior performance of sinistrals compared to dextrals. On these two tasks, there was also a moderate relationship between handedness scores and performance measures. Third, a computer-based task of adjusting scaled body-outline-halves showed no handedness differences. Overall, these findings suggest handedness differences in the implicit but not explicit representation of one’s own body space. Possible mechanisms underlying the handedness differences shown for the implicit tasks are a stronger lateralization or a greater activation imbalance for dextrals and/or greater access to right hemispheric functions, such as an “up-to-date body” representation, by sinistrals. In contrast, explicit measures of how body space is represented may not be affected due to their relying on a different processing pathway.     

The space between us: stereotype threat and distance in interracial contexts

Four studies investigate the role that stereotype threat plays in producing racial distancing behavior in an anticipated conversation paradigm. It was hypothesized that the threat of appearing racist may have the ironic effect of causing Whites to distance themselves from Black conversation partners. In Study 1, participants distanced themselves more from Black partners under conditions of threat, and this distance correlated with the activation of a "White racist" stereotype. In Study 2, it was demonstrated that Whites' interracial distancing behavior was not predicted by explicit or implicit prejudice. Study 3 provides evidence that conceiving of interracial interactions as opportunities to learn may attenuate the negative consequences of threat for Whites. Study 4 found that Whites have conscious access to their experience of stereotype threat and that this awareness may mediate the relationship between threat and distance. These results are discussed within a broader discourse of racial distancing and the possibility that certain identity threats may be as important as prejudice in determining the outcomes of interracial interactions.     

Correcting distance estimates by interacting with immersive virtual environments: effects of task and available sensory information

The tendency to underestimate egocentric distances in immersive virtual environments (VEs) is not well understood. However, previous research (A. R. Richardson & D. Waller, 2007) has demonstrated that a brief period of interaction with the VE prior to making distance judgments can effectively eliminate subsequent underestimation. Here the authors examine the mechanism underlying the effect of VE interaction and the conditions that may give rise to it. In Experiment 1, after interacting with an immersive VE, participants tended to overestimate distances in the physical world, indicating that the interaction involved a recalibration of the perceptual-motor system. Experiment 2 demonstrates that visual information is not necessary (and that body-based information is necessary) during the interaction period for it to have a positive effect on subsequent distance estimation accuracy. Experiment 3 illustrates that the interaction task does not need to be goal directed in order to be effective.     

Depth perception in virtual reality: distance estimations in peri- and extrapersonal space.

The present study investigated depth perception in virtual environments. Twenty-three participants verbally estimated ten distances between 40 cm and 500 cm in three different virtual environments in two conditions: (1) only one target was presented or (2) ten targets were presented at the same time. Additionally, the presence of a metric aid was varied. A questionnaire assessed subjective ratings about physical complaints (e.g., headache), the experience in the virtual world (e.g., presence), and the experiment itself (self-evaluation of the estimations). Results show that participants underestimate the virtual distances but are able to perceive the distances in the right metric order even when only very simple virtual environments are presented. Furthermore, interindividual differences and intraindividual stabilities can be found among participants, and neither the three different virtual environments nor the metric aid improved depth estimations. Estimation performance is better in peripersonal than in extrapersonal space. In contrast, subjective ratings provide a preferred space: a closed room with visible floor, ceiling, and walls.     

Comparing power imagery in TATs written by hand or on the computer

Two barriers to the use of the Thematic Apperception Test (TAT) in motivation research were addressed: its low internal consistency and its time-consuming coding system. Sixty males and 60 females wrote five stories to TAT pictures either on the computer or by hand. Half of each group were timed and half untimed. The writing of stories was guided by four sets of questions, and stories were coded for need for power (n Pow) by the corresponding four paragraphs. Cronbach’s alpha for the five stories was .46; for the 20 paragraphs, Cronbach’s alpha was .65. We conclude that, to the extent that measuring internal consistency is appropriate for a thought-sampling instrument like the TAT, internal consistency should be calculated by paragraphs. Significantly more words were produced in the untimed condition, but n Pow did not differ by gender, hand-written versus computer-written, or timed versus untimed conditions. The five pictures elicited significantly different amounts of n Pow. It is recommended that researchers who give the TAT on the computer use the untimed condition. Suggestions are made for increasing the scoring validity and for using the computer to decrease the time required for human coders.     

Activity of common marmosets (Callithrix jacchus) in limited spaces: hand movement characteristics

The increasing popularity of marmoset monkeys (Callithrix jacchus) in anatomical, behavioral, and electrophysiological studies has called for a detailed analysis of their natural behavior within limited spaces. In the present study, the authors analyzed hand movements during horizontal and vertical progressions in a cylinder. The trajectory of each hand covered the entire cylinder floor during horizontal progressions and the entire cylinder wall during vertical progressions. Different marmosets have different patterns of hand movement. The average maximum angle of hand movements for all marmosets during horizontal and vertical progressions oscillates, although the average over time is constant and similar for both hands, whereas head movements during horizontal progressions become smaller with successive progressions. Another observed difference between rats and monkeys was in the size of head and hand movements at the beginning of each experimental session. During the 1st horizontal progression, all marmosets moved their heads to a greater extent than their hands. This sequential head and hand movement is referred as bistable behavior. The bistable pattern of motor behavior, which was also observed in successive progressions, may be derived from an inherent fear of predators or exploratory interest of a novel environment.     

Discretionary task interleaving: heuristics for time allocation in cognitive foraging

When participants allocated time across 2 tasks (in which they generated as many words as possible from a fixed set of letters), they made frequent switches. This allowed them to allocate more time to the more productive task (i.e., the set of letters from which more words could be generated) even though times between the last word and the switch decision ("giving-up times") were higher in the less productive task. These findings were reliable across 2 experiments using Scrabble tasks and 1 experiment using word-search puzzles. Switch decisions appeared relatively unaffected by the ease of the competing task or by explicit information about tasks' potential gain. The authors propose that switch decisions reflected a dual orientation to the experimental tasks. First, there was a sensitivity to continuous rate of return--an information-foraging orientation that produced a tendency to switch in keeping with R. F. Green's (1984) rule and a tendency to stay longer in more rewarding tasks. Second, there was a tendency to switch tasks after subgoal completion. A model combining these tendencies predicted all the reliable effects in the experimental data.     

The influence of restricted viewing conditions on egocentric distance perception: implications for real and virtual indoor environments

We carried out three experiments to examine the influence of field of view and binocular viewing restrictions on absolute distance perception in real-world indoor environments. Few of the classical visual cues provide direct information for accurate absolute distance judgments to points in the environment beyond about 2 m from the viewer. Nevertheless, in previous work it has been found that visually directed walking tasks reveal accurate distance estimations in full-cue real-world environments to distances up to 20 m. In contrast, the same tasks in virtual environments produced with head-mounted displays (HMDs) show large compression of distance. Field of view and binocular viewing are common limitations in research with HMDs, and have been rarely studied under full pictorial-cue conditions in the context of distance perception in the real-world. Experiment 1 showed that the view of one's body and feet on the floor was not necessary for accurate distance perception. In experiment 2 we manipulated the horizontal and the vertical field of view along with head rotation and found that a restricted field of view did not affect the accuracy of distance estimations when head movement was allowed. Experiment 3 showed that performance with monocular viewing was equal to that with binocular viewing. These results have implications for the information needed to scale egocentric distance in the real-world and reduce the support for the hypothesis that a limited field of view or imperfections in binocular image presentation are the cause of the underestimation seen with HMDs.     

Eye movement guidance in reading: the role of parafoveal letter and space information

The relation between parafoveal letter and space information in eye movement guidance during reading was investigated in 2 experiments. Contingent upon the reader's fixation, the type of parafoveal information available to the right of fixation was varied by (a) space information only, (b) space information with letter information added at some delay, or (c) letter and space information simultaneously. In addition, the onset of the relevant parafoveal information was delayed between 0 and 250 ms into the fixation. The time course of processing the 2 types of information (letters or spaces) differed, as did the nature of their impact on the eye movement record. Although both letter and space information influenced saccade length and initial landing positions within words, only letter information had an effect on fixation duration. In addition, fixation duration was affected only by information entering within the first 50 ms of the fixation, whereas saccade length was affected by information arriving at any time during the fixation. The results are consistent with a model of eye movement control in which 2 independent processes are operating in tandem to determine when and where to move the eyes during reading.