Mental object rotation and the planning of hand movements.

Recently, we showed that the simultaneous execution of rotational hand movements interferes with mental object rotation, provided that the axes of rotation coincide in space. We hypothesized that mental object rotation and the programming of rotational hand movements share a common process presumably involved in action planning. Two experiments are reported here that show that the mere planning of a rotational hand movement is sufficient to cause interference with mental object rotation. Subjects had to plan different spatially directed hand movements that they were asked to execute only after they had solved a mental object rotation task. Experiment 1 showed that mental object rotation was slower if hand movements were planned in a direction opposite to the presumed mental rotation direction, but only if the axes of hand rotation and mental object rotation were parallel in space. Experiment 2 showed that this interference occurred independent of the preparatory hand movements observed in Experiment 1. Thus, it is the planning of hand movements and not their preparation or execution that interferes with mental object rotation. This finding underlines the idea that mental object rotation is an imagined (covert) action, rather than a pure visual-spatial imagery task, and that the interference between mental object rotation and rotational hand movements is an interference between goals of actions.     

Object-based processes in the planning of goal-directed hand movements

Theories in motor control suggest that the parameters specified during the planning of goal-directed hand movements to a visual target are defined in spatial parameters like direction and amplitude. Recent findings in the visual attention literature, however, argue widely for early object-based selection processes. The present experiments were designed to examine the contributions of object-based and space-based selection processes to the preparation time of goal-directed pointing movements. Therefore, a cue was presented at a specific location. The question addressed was whether the initiation of responses to uncued target stimuli could benefit from being either within the same object (object based) or presented at the same direction (space based). Experiment 1 replicated earlier findings of object-based benefits for non-goal-directed responses. Experiment 2 confirmed earlier findings of space-based benefits for goal-directed hand pointing movements. In Experiments 3 and 4, space-based and object-based manipulations were combined while requiring goal-directed hand pointing movements. The results clearly favour the notion that the selection processes for goal-directed pointing movements are primarily object based. Implications for theories on selective attention and action planning are discussed.     

被试自身人手初始状态对心理旋转加工的影响：眼动研

利用眼动追踪技术,探讨在左右手判断任务条件下人手心理旋转加工是否受到被试自身人手初始状态的影响。两个实验的反应时数据和眼动数据均发现：（1）心理旋转加工受被试自身人手初始状态的影响,表现出一致性效应;（2）显著的内旋效应;（3）被试心理旋转加工时注视点取样存在着不均衡性。这些结果表明：在左右手判断任务中,心理旋转加工的对象是被试自身人手的表象,是自我参照的心理旋转,并且内旋效应是由被试对自身人手表象进行旋转时受到人手生理机制约束所致,而不是被试旋转刺激图片的表象由“生理机制约束知识”影响所致     

Planning of reach-and-grasp movements: effects of validity and type of object information

Individuals are assumed to plan reach-and-grasp movements by using two separate processes. In 1 of the processes, extrinsic (direction, distance) object information is used in planning the movement of the arm that transports the hand to the target location (transport planning); whereas in the other, intrinsic (shape) object information is used in planning the preshaping of the hand and the grasping of the target object (manipulation planning). In 2 experiments, the authors used primes to provide information to participants (N = 5, Experiment 1; N = 6, Experiment 2) about extrinsic and intrinsic object properties. The validity of the prime information was systematically varied. The primes were succeeded by a cue, which always correctly identified the location and shape of the target object. Reaction times were recorded. Four models of transport and manipulation planning were tested. The only model that was consistent with the data was 1 in which arm transport and object manipulation planning were postulated to be independent processes that operate partially in parallel. The authors suggest that the processes involved in motor planning before execution are primarily concerned with the geometric aspects of the upcoming movement but not with the temporal details of its execution.     

Planning of Reach-and-Grasp Movements: Effects of Validity and Type of Object Information

Individuals are assumed to plan reach-and-grasp movements by using two separate processes. In 1 of the processes, extrinsic (direction, distance) object information is used in planning the movement of the arm that transports the hand to the target location (transport planning); whereas in the other, intrinsic (shape) object information is used in planning the preshaping of the hand and the grasping of the target object (manipulation planning) In 2 experiments, the authors used primes to provide information to participants (N = 5, Experiment 1; N = 6, Experiment 2) about extrinsic and intrinsic object properties. The validity of the prime information was systematically varied. The primes were succeeded by a cue, which always correctly identified the location and shape of the target object. Reaction times were recorded. Four models of transport and manipulation planning were tested. The only model that was consistent with the data was 1 in which arm transport and object manipulation planning were postulated to be independent processes that operate partially in parallel. The authors suggest that the processes involved in motor planning before execution are primarily concerned with the geometric aspects of the upcoming movement but not with the temporal details of its execution.     

Tool use and the effect of action on the imagination

Three studies examined the claim that hand movements can facilitate imagery for object rotations but that this facilitation depends on people's model of the situation. In Experiment 1, physically turning a block without vision reduced mental rotation times compared with imagining the same rotation without bodily movement. In Experiment 2, pulling a string from a spool facilitated participants' mental rotation of an object sitting on the spool. In Experiment 3, depending on participants' model of the spool, the exact same pulling movement facilitated or interfered with the exact same imagery transformation. Results of Experiments 2 and 3 indicate that the geometric characteristics of an action do not specify the trajectory of an imagery transformation. Instead, they point to people's ability to model the tools that mediate between motor activity and its environmental consequences and to transfer tool knowledge to a new situation.     

The relationship between mental rotation and representational momentum

Two experiments explored a possible relationship between mental rotation and representational momentum, a task in which participants were asked to remember an object's position following a sequence of images implying motion. Typically, participants misremember the position as distorted forward along the implied trajectory. If representational momentum relies on mental imagery, the magnitude of memory distortion in a representational momentum task should be positively correlated with the rate of mental rotation. As predicted, faster mental rotation rates and larger memory distortions for object position were observed for rotational axes aligned with the viewers' coordinate system. In addition, participants with slower mental rotation rates produced smaller memory distortions in the implied-event task.     

Motor Processes in Children's Mental Rotation

Previous studies with adult human participants revealed that motor activities can influence mental rotation of body parts and abstract shapes. In this study, we investigated the influence of a rotational hand movement on mental rotation performance from a developmental perspective. Children at the age of 5, 8, and 11 years and adults performed a mental rotation task while simultaneously rotating their hand (guided by a handle). The direction of the manual rotation was either compatible or incompatible with the direction of the mental rotation. Response times increased with increasing stimulus orientation angles, indicating that participants of all age groups used mental rotation to perform the task. A differential effect of the compatibility of manual rotation and mental rotation was found for 5-year-olds and 8-year-olds, but not for 11-year-olds and adults. The results of this study suggest that the ability to dissociate motor from visual cognitive processes increases with age.     

Interference effects demonstrate distinct roles for visual and motor imagery during the mental representation of human action

Four experiments were completed to characterize the utilization of visual imagery and motor imagery during the mental representation of human action. In Experiment 1, movement time functions for a motor imagery human locomotion task conformed to a speed-accuracy trade-off similar to Fitts' Law, whereas those for a visual imagery object motion task did not. However, modality-specific interference effects in Experiment 2 demonstrate visual and motor imagery as cooperative processes when the action represented is tied to visual coordinates in space. Biomechanic-specific motor interference effects found in Experiment 3 suggest one basis for separation of processing channels within motor imagery. Finally, in Experiment 4 representations of motor actions were found to be generated using only visual imagery under certain circumstances: namely, when the imaginer represented the motor action of another individual while placed at an opposing viewpoint. These results suggest that the modality of representation recruited to generate images of human action is dependent on the dynamic relationship between the individual, movement, and environment.     

An action sequence withheld in memory can delay execution of visually guided actions: the generalization of response compatibility interference

Withholding an action plan in memory for later execution can delay execution of another action, if the actions share a similar (compatible) action feature (i.e., response hand). This phenomenon, termed compatibility interference (CI), was found for identity-based actions that do not require visual guidance. The authors examined whether CI can generalize to both identity-based and location-based actions that require visual guidance. Participants withheld a planned action based on the identity of a stimulus and then immediately executed a visually guided action (touch response) to a 2nd stimulus based on its color identity (Experiment 1), its spatial location (Experiment 2), or an intrinsic spatial location within an object (Experiment 3). Results showed CI for both left- and right-hand responses in Experiment 1. However, CI occurred for left- but not right-hand responses in Experiment 2 and 3. This suggests that CI can generalize to visually guided actions under cognitive control but not to actions that invoke automatic visual-control mechanisms where the left hemisphere may play a special role (C. Gonzalez, T. Ganel, & M. Goodale, 2006). The code occupation account for CI (G. Stoet & B. Hommel, 2002) is also discussed.     

What part of an action interferes with ongoing perception?

Recent studies have demonstrated specific interference effects between concurrent perception and action. In the following we address the possible causes of such effects by employing a continuous paradigm in which participants were asked to produce movements in a specified direction and to judge the direction of a concurrently presented stimulus motion. In such paradigms, a repulsion of the perceived by the produced movement direction is typically observed. The first question addressed in the current study was whether passive displacements of the hand would be sufficient for inducing the repulsion effect. This was done by sometimes moving the participants' hands with a robot. No repulsion effect was found for these passive movements, which shows that the integration of visual and proprioceptive information is not sufficient for repulsion to arise. However, repulsion was present for active movements, that is when participants intended to move. In a second experiment, participants' movements were sometimes unexpectedly blocked by a robot. No repulsion was observed in the blocked condition. We conclude that the intention to move (Experiment 1) and actual movement execution (Experiment 2) are both necessary preconditions for this type of specific interference to arise in continuous and concurrent perception-action tasks.     

The Simon effect with wheel-rotation responses

The authors examined clockwise and counterclockwise wheel-rotation responses to high- or low-pitched tones presented in participants' (N = 96, Experiment 1; N = 48, Experiment 2; N = 48, Experiment 3) left and right ears. In Experiment 1, a Simon effect (fastest responding when tone location and direction of wheel turn corresponded) was obtained when participants' hands were at the top or middle of the wheel but not at the bottom. With the bottom hand placement, a Simon effect was induced by instructions emphasizing hand movements but not by instructions emphasizing wheel movements (Experiment 2), and by a visual cursor controlled by the wheel but not one triggered by the response (Experiment 3). The results of the experiments showed that the nature of the task and the instructed action goal influence the direction of the Simon effect.     

On the relation between spontaneous perspective taking and other visuospatial processes

Common processes and representations engaged by visuospatial tasks were investigated by looking at four frequently used visuospatial research paradigms, the aim being to contribute to a better understanding of which specific processes are addressed in the different paradigms compared. In particular, the relation between spontaneous and instructed perspective taking, as well as mental rotation of body-part/non-body-part objects, was investigated. To this end, participants watched animations that have been shown to lead to spontaneous perspective taking. While they were watching these animations, participants were asked to explicitly adopt another perspective (Experiment 1), perform a mental object rotation task that involved a non-body-part object (Experiment 2), or perform a mental rotation of a body-part object (Experiment 3). Patterns of interference between the tasks, reflected in the reaction time patterns, showed that spontaneous and instructed perspective taking rely on similar representational elements to encode orientation. By contrast, no such overlap was found between spontaneous perspective taking and the rotation of non-body-part objects. Also, no overlap in orientation representation was evident with mental body-part rotations. Instead of an overlap in orientation representations, the results suggest that spontaneous perspective taking and the mental rotation of body parts rely on similar—presumably, motor—processes. These findings support the view that motor processes are involved in perspective taking and mental rotation of body parts.     

Performance of unimanual and bimanual multiphased prehensile movements

By manipulating task action demands in 2 experiments, the author investigated whether the context-dependent effects seen in unimanual multiphase movements are also present in bimanual movements. Participants (N = 14) in Experiment 1 either placed or tossed objects into targets. The results indicated that the intention to perform a subsequent action with an object could influence the performance of an earlier movement in a sequence in both unimanual and bimanual tasks. Furthermore, assimilation effects were found when the subsequent tasks being performed by the 2 hands were incongruent. In Experiment 2, the author investigated in 12 participants whether planning in a multiphase movement includes some representation of the accuracy demands of the subsequent task. The accuracy demands of a subsequent task did not appear to influence initial movement planning. Instead, the present results support the notion that it is the action requirements of the subsequent movement that lead to context-dependent effects.     

Impact of planned movement direction on judgments of visual locations

The present study examined if and how the direction of planned hand movements affects the perceived direction of visual stimuli. In three experiments participants prepared hand movements that deviated regarding direction (“Experiment 1” and “2”) or distance relative to a visual target position (“Experiment 3”). Before actual execution of the movement, the direction of the visual stimulus had to be estimated by means of a method of adjustment. The perception of stimulus direction was biased away from planned movement direction, such that with leftward movements stimuli appeared somewhat more rightward than with rightward movements. Control conditions revealed that this effect was neither a mere response bias, nor a result of processing or memorizing movement cues. Also, shifting the focus of attention toward a cued location in space was not sufficient to induce the perceptual bias observed under conditions of movement preparation (“Experiment 4”). These results confirm that characteristics of planned actions bias visual perception, with the direction of bias (contrast or assimilation) possibly depending on the type of the representations (categorical or metric) involved.     

A common first-order time-to-contact based control of hand-closure initiation in catching and grasping

To catch or grasp an object, the initiation of hand closure has to be coordinated with the relative movement between hand and object. In search of a common control of the initiation of hand closure for both tasks (van de Kamp, Bongers, & Zaal, 2010), the authors studied two tasks, catching while keeping the hand stationary and prehension. They showed that the initiation of hand closure could well be based on first-order time-to-contact in the prehension task but not in the catching task studied. The current study tested if the fact that the hand-object gap was closed at a linear rate made that the initiation of hand closure could not be explained on the basis of that same first-order time-to-contact in the catching task. In Experiment 1, the participants had to catch targets that approached at nonlinear rates while keeping the hand stationary. In Experiment 2, the participants were free to move their hand in catching the approaching objects, allowing the closure of the hand-object gap to occur at a nonlinear rate as it would in natural movements. The results showed that the first-order time-to-contact based control of the initiation of hand closure did apply in Experiment 2, whereas it did not in Experiment 1. It was concluded that constraining the catching task such that it became unfamiliar led to a hampered timing, thus obstructing the finding of the common control in the previous study, and in Experiment 1 of the current study.     

Angular velocity discrimination

Three experiments were designed to investigate naive observers' abilities at discriminating the rotational velocities of two simultaneously viewed objects. In Experiment 1, rotations could occur about parallel or orthogonal axes, with initial orientations in phase or out of phase, and (for parallel rotational axes) in the same or opposite direction. Differential thresholds were approximately 10%. In Experiment 2, stimulus objects differed in the number of faces revealed in rotation (three vs. four). Observers' response curves had no greater spread, but their PSEs (points of subjective equality) were shifted such that there was a partial compensation for faces revealed per unit time. In both Experiment 1 and Experiment 2, performance was consistent across rotational axis and directional conditions. In Experiment 3, the effect of object size was examined, in order to determine the extent to which angular velocity judgments are influenced by the tangential velocity of the faces. When the comparison cube's edges were half the length of the standard's, PSEs were elevated 18.5%. Taken together, these data suggest that observers are able to discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.     

Visual working memory as the substrate for mental rotation

In mental rotation, a mental representation of an object must be rotated while the actual object remains visible. Where is this representation stored while it is being rotated? To answer this question, observers were asked to perform a mental rotation task during the delay interval of a visual working memory task. When the working memory task required the storage of object features, substantial bidirectional interference was observed between the memory and rotation tasks, and the interference increased with the degree of rotation. However, rotation-dependent interference was not observed when a spatial working memory task was used instead of an object working memory task. Thus, the object working memory subsystem—not the spatial working memory subsystem—provides the buffer in which object representations are stored while they undergo mental rotation. More broadly, the nature of the information being stored—not the nature of the operations performed on this information—may determine which subsystem stores the information.     

The Simon Effect With Wheel-Rotation Responses

The authors examined clockwise and counterclockwise wheel-rotation responses to high- or low-pitched tones presented in participants' (N = 96, Experiment 1; N = 48, Experiment 2; N = 48, Experiment 3) left and right ears. In Experiment 1, a Simon effect (fastest responding when tone location and direction of wheel turn corresponded) was obtained when participants' hands were at the top or middle of the wheel but not at the bottom. With line bottom hand placement, a Simon effect was induced by instructions emphasizing hand movements but not by instructions emphasizing wheel movements (Experiment 2), and by a visual cursor controlled by the wheel but not one triggered by the response (Experiment 3). The results of the experiments showed that the nature of the task and the instructed action goal influence the direction of the Simon effect.     

Motor resources in peripersonal space are intrinsic to spatial encoding: Evidence from motor interference

The aim of this study was to explore the role of motor resources in peripersonal space encoding: are they intrinsic to spatial processes or due to action potentiality of objects? To answer this question, we disentangled the effects of motor resources on object manipulability and spatial processing in peripersonal and extrapersonal spaces. Participants had to localize manipulable and non-manipulable 3-D stimuli presented within peripersonal or extrapersonal spaces of an immersive virtual reality scenario. To assess the contribution of motor resources to the spatial task a motor interference paradigm was used. In Experiment 1, localization judgments were provided with the left hand while the right dominant arm could be free or blocked. Results showed that participants were faster and more accurate in localizing both manipulable and non-manipulable stimuli in peripersonal space with their arms free. On the other hand, in extrapersonal space there was no significant effect of motor interference. Experiment 2 replicated these results by using alternatively both hands to give the response and controlling the possible effect of the orientation of object handles. Overall, the pattern of results suggests that the encoding of peripersonal space involves motor processes per se, and not because of the presence of manipulable stimuli. It is argued that this motor grounding reflects the adaptive need of anticipating what may happen near the body and preparing to react in time.