Conscious awareness of action potentiates sensorimotor learning.

Many everyday skills are unconsciously learned through repetitions of the same behaviour by binding independent motor acts into unified sets of actions. However, our ability to be consciously aware of producing newly and highly trained motor skills raises the question of the role played by conscious awareness of action upon skill acquisition. In this study we strengthened conscious awareness of self-produced sequential finger movements by way of asking participants to judge their performance in terms of maximal fluency after each trial. Control conditions in which participants did not make any judgment or performance-unrelated judgments were also included. Findings indicate that conscious awareness of action, enhanced via subjective appraisal of motor efficiency, potentiates sensorimotor learning and skilful motor production in optimising the processing and sequencing of action units, as compared to the control groups. The current work lends support to the claim that the learning and skilful expression of sensorimotor behaviours might be grounded upon our ability to be consciously aware of our own motor capability and efficiency.

Tool characteristics in imagery of tool actions.

Are tool characteristics represented in imagined tool actions? In two experiments participants imagined and executed coloring rectangles with a thick and a thin pen. In Experiment 2, an additional execution condition without visual feedback of coloring allowed us to dissociate between the relevance of kinesthetic and visual feedback. Pen thickness influenced coloring durations in all conditions, indicating that characteristics of a simple tool are represented during imagery. Imagination was shorter than execution, indicating that imagination may be less detailed than execution. Execution without visual feedback was even shorter than imagination, indicating that vision is more important than kinesthesis for differences between imagination and execution, and that either imagining the movement, inhibiting movement execution or imagining the progress of the action is effortful during imagery. In conclusion, characteristics of simple tools are represented in imagined tool actions but the representation of tools' effects may not always be adequate.

Using scissors to bisect a line: a perception-action dissociation in complex tool use.

Previous research has shown that unilateral visual neglect is improved when patients are required to actively grasp an object at its center, rather than only pointing to its center. A similar dissociation between pointing and grasping responses has been reported for pseudoneglect, a spatial bias toward the left side of space that is normally exhibited by healthy participants. Among other theories, the two-visual-streams hypothesis has been offered as an explanation for these dissociations. According to this hypothesis, highly practiced actions that are performed under easily available visual input (e.g., grasping an object) are controlled by the dorsal stream and can resist perceptual judgment biases. We investigated whether, in pseudoneglect, dissociations between perceptual judgments and motor-manipulative responses occur when participants have to respond with complex tools that are highly practiced but that have been shown to rely on both ventral- and dorsal-stream processing. In a standard line bisection task, participants had to either mark the center of a line with a pencil or cut the line in two halves using a pair of scissors. The results indicated the typical leftward bias (pseudoneglect) in the pencil task, whereas performance was much more accurate in the scissors task. These results show that actions featuring complex tool use can resist perceptual judgment biases, and the findings are discussed with reference to existing accounts of perception-action dissociations.

Modality-specific organization in the representation of sensorimotor sequences.

Sensorimotor representations of movement sequences are hierarchically organized. Here we test the effects of different stimulus modalities on such organizations. In the visual group, participants responded to a repeated sequence of visually presented stimuli by depressing spatially compatible keys on a response pad. In the auditory group, learners were required to respond to auditorily presented stimuli, which had no direct spatial correspondence with the response keys: the lowest pitch corresponded to the leftmost key and the highest pitch to the rightmost key. We demonstrate that hierarchically and auto-organized sensorimotor representations are developed through practice, which are specific both to individuals and stimulus modalities. These findings highlight the dynamic and sensory-specific modulation of chunk processing during sensorimotor learning - sensorimotor chunking - and provide evidence that modality-specific mechanisms underlie the hierarchical organization of sequence representations.

Action-sentence compatibility: the role of action effects and timing.

Research on embodied approaches to language comprehension suggests that we understand linguistic descriptions of actions by mentally simulating these actions. Evidence is provided by the action-sentence compatibility effect (ACE) which shows that sensibility judgments for sentences are faster when the direction of the described action matches the response direction. In two experiments, we investigated whether the ACE relies on actions or on intended action effects. Participants gave sensibility judgments of auditorily presented sentences by producing an action effect on a screen at a location near the body or far from the body. These action effects were achieved by pressing a response button that was located in either the same spatial direction as the action effect, or in the opposite direction. We used a go/no-go task in which the direction of the to-be-produced action effect was either cued at the onset of each sentence (Experiment 1) or at different points in time before and after sentence onset (Experiment 2). Overall, results showed a relationship between the direction of the described action and the direction of the action effect. Furthermore, Experiment 2 indicated that depending on the timing between cue presentation and sentence onset, participants responded either faster when the direction of the described action matched the direction of the action effect (positive ACE), or slower (negative ACE). These results provide evidence that the comprehension of action sentences involves the activation of representations of action effects. Concurrently activated representations in sentence comprehension and action planning can lead to both priming and interference, which is discussed in the context of the theory of event coding.

Bimanual interference associated with handling different tool transformations.

Research on bimanual coordination of hand movements has identified several loci of bimanual interference, including interference because of programming different movement parameters or selecting different targets for the two hands. This study investigates the extent and origin of interference when participants execute bimanual actions with tools. In the experiments, participants moved two tools, one with each hand, to two directly cued target locations. One type of tool transformed the body movement into a spatially compatible movement of the effective part of the tool, whereas the other transformed it into a spatially incompatible movement. Tool transformations for the two hands were either the same or different. Furthermore, target locations were either in the same or in different spatial directions. Results indicated significantly shorter reaction times (RTs) and less errors when tool transformations were the same for both hands. In addition, movements were initiated more quickly and less error-prone when targets were in the same direction, but this effect was modulated by the congruency of the two lever transformations. Investigations of the time course of the effects revealed that they were not because of early perceptual processing (Experiment 2). Furthermore, the general pattern of results occurred for different grip positions (Experiment 3) and different lever types (Experiment 4), suggesting that it reflects rather general constraints in bimanual coordination of tool-use actions.

What to do and how to do it: action representations in tool use.

Research on bimanual coordination has shown that the efficiency of programming an action is determined by the way the action is cognitively represented. In tool use, actions can be represented with respect to the spatial goal of the action (e.g., the nail that is to be hit by a hammer) or with respect to the tool and its transformation (i.e., the function that maps external target locations onto corresponding bodily movements). We investigated whether the way of cuing bimanual actions with tools affects their cognitive representation and the efficiency with which they are programmed. In one group of participants, tool transformations were specified by symbolic cues, whereas the targets were indicated by direct spatial cues. In another group of participants, symbolic cues specified the targets of the tool-use actions, whereas tool transformations were indicated by direct spatial cues. In a third group, both targets and tool transformations were cued directly by spatial cues. It was hypothesized that different cognitive representations would result in more or less efficient programming of the action. Results indicated longer reaction times and a higher error rate in the group with symbolic cuing of the targets as compared to the group with symbolic cuing of the transformations. The latter did not differ much from the direct cuing group. These results suggest that it is more efficient to represent bimanual tool-use actions in terms of the tool transformations involved than in terms of the targets at which they are directed.

Coordinative constraints in bimanual tool use.

This study investigates coordinative constraints when participants execute discrete bimanual tool use actions. Participants moved two levers to targets that were either presented near the proximal parts of the levers or near the distal tips of the levers. In the first case, the tool transformation (i.e. the relationship between hand movement direction and target direction) was compatible, whereas in the second case, it was incompatible. We hypothesized that an egocentric constraint (i.e. a preference for moving the hands and tools in a mirror-symmetrical fashion) would be dominant when targets are presented near the proximal parts of the levers because in this situation, movements can be coded in terms of body-related coordinates. Furthermore, an allocentric constraint (i.e. a preference to move the hands in the same (parallel) direction in extrinsic space) was expected to be dominant when one of the targets or both are presented near the distal parts of the levers because in this condition, movements have to be coded in an external reference frame. The results show that when both targets are presented near the proximal parts of the levers, participants are faster and produce less errors with mirror-symmetrical when compared to parallel movements. Furthermore, the RT mirror-symmetry advantage is eliminated, when both targets are presented near the distal parts of the levers, and it is reversed, when the target for one lever is presented near its distal part and the target for the other lever is presented near its proximal part. These results show that the dominance of egocentric and allocentric coordinative constraints in bimanual tool use depends on whether movements are coded in terms of body-related coordinates or in an external reference frame.

Bimanual interference with compatible and incompatible tool transformations.

The present study investigates bimanual interference in a tool-use task, in which two target locations had to be touched concurrently with two tools, one for each hand. Target locations were either in the same, or in different directions for the two hands. Furthermore, the tools implemented either a compatible or an incompatible relationship between the direction of target locations and the direction of associated bodily movements. Results indicated bimanual interference when the tools had to be moved to targets in different directions. Furthermore, this interference was much more pronounced when the tools required body movements that were spatially incompatible to the cued target locations as compared to when they were compatible. These results show that incompatible relationships between target directions and bodily movement directions can aggravate bimanual interference in tool use.

Embodied rules in tool use: a tool-switching study.

In tool use, a transformation rule defines the relation between an operating movement and its distal effect. This rule is determined by the tool structure and requires no explicit definition. The present study investigates how humans represent and apply compatible and incompatible transformation rules in tool use. In Experiment 1, participants had to switch between tools for which the respective transformation rules were either the same or different. This way, rule repetitions could be dissociated from tool repetitions. In Experiment 2, the application of transformation rules in tool use was compared with the application of explicitly defined rules. In Experiment 3, actions of tool use were cued either by tool pictures or by written tool names. The results suggest that a transformation rule in tool use has a cognitive representation that is independent of the concrete tool incorporating it. Furthermore, its application differs from the application of an explicitly defined rule in terms of reduced top-down processing.

Observing human interaction with physical devices.

Previous study has shown that if we observe another person operating a tool or physical device, then the action rule of the observed action is automatically activated and can subsequently facilitate own actions. In this study, the mechanisms responsible for this automatic priming of actions are investigated. In two experiments, the question is raised whether priming arises from the observation of the physical device and its movements, or whether it is modulated by aspects of the person's behaviour. Whereas experiment 1 shows that priming effects are not influenced by the effector used by the observed person, experiment 2 demonstrates that they are modulated by the handle (and associated action rule) that is used to operate the device. These results suggest that motor resonance mechanisms are sensitive to the specific interaction between movements of an actor and associated movements of a physical device.

Movements, actions and tool-use actions: an ideomotor approach to imitation.

In this article we discuss both merits and limitations of the ideomotor approach to action control and action imitation. In the first part, we give a brief outline of ideomotor theory and its functional implications for imitation and related kinds of behaviours. In the subsequent sections, we summarize pertinent experimental studies on action imitation and action induction. These studies show that action perception modulates action planning in a number of ways, of which imitation is but one. In the last part, we move from regular actions to tool-use actions, raising the issue of whether and how watching others' tool-use actions leads to corresponding behaviours in observers. Here, we discuss experiments aimed at dissociating the relative roles of environmental targets, bodily movements and target-to-movement-mappings (action rules) in the observation of tool-use actions. Our findings indicate a strong role for action rules in the observation and imitation of tool-use actions. We argue that, in order to account for these findings, ideomotor theory needs to be extended to take mappings between bodily movements and environmental effects into account.

Effects of instruction on learners' ability to generate an effective pathway in the method of loci.

One of the most effective mnemonic techniques is the well-known method of loci. Learning and retention, especially of sequentially ordered information, is facilitated by this technique which involves mentally combining salient loci on a well-known path with the material to be learned. There are several variants of this technique that differ in the kind of path that is suggested to the user and it is implicitly assumed that these variants are comparable in effectiveness. The experiments reported in this study were designed to test this assumption. The data of two experiments show that participants who are instructed to generate and apply loci on a route to their work recall significantly more items in a memory test than participants who are instructed to generate and apply loci on a route in their house. These results have practical implications for the instruction and application of the method of loci.

Action planning with two-handed tools.

In tool use, the intended external goals have to be transformed into bodily movements by taking into account the target-to-movement mapping implemented by the tool. In bimanual tool use, this mapping may depend on the part of the tool that is operated and the effector used (e.g. the left and right hand at the handle bar moving in opposite directions in order to generate the same bicycle movement). In our study, we investigated whether participants represent the behaviour of the tool or only the effector-specific mapping when using two-handed tools. In three experiments, participants touched target locations with a two-jointed lever, using either the left or the right hand. In one condition, the joint of the lever was constant and switching between hands was associated with switching the target-to-movement-mapping, whereas in another condition, switching between hands was associated with switching the joint, but the target-to-movement-mapping remained constant. Results indicate pronounced costs of switching hands in the condition with constant joint, whereas they were smaller with constant target-to-movement mapping. These results suggest that participants have tool-independent representations of the effector-specific mappings.

The effect of continuous, nonlinearly transformed visual feedback on rapid aiming movements.

We investigated the ability to adjust to nonlinear transformations that allow people to control external systems like machines and tools. Earlier research (Verwey and Heuer 2007) showed that in the presence of just terminal feedback participants develop an internal model of such transformations that operates at a relatively early processing level (before or at amplitude specification). In this study, we investigated the level of operation of the internal model after practicing with continuous visual feedback. Participants executed rapid aiming movements, for which a nonlinear relationship existed between the target amplitude seen on the computer screen and the required movement amplitude of the hand on a digitizing tablet. Participants adjusted to the external transformation by developing an internal model. Despite continuous feedback, explicit awareness of the transformation did not develop and the internal model still operated at the same early processing level as with terminal feedback. Thus with rapid aiming movements, the type of feedback may not matter for the locus of operation of the internal model.

What to do and how to do it: sequence learning of action effects and transformation rules.

Many goal-oriented actions, for example in tool use, can be characterized by the involvement of two components: The effect that the acting person wants to achieve and the transformation rule that defines the relationship between a bodily movement and the associated action effect. Both in conjunction specify the concrete action that has to be executed. In our experiments, we utilized a sequence learning paradigm to investigate whether these components are represented separately or are bound together to form a more holistic representation of the action. Participants switched between different transformation rules to achieve certain action effects. In one group, there was a fixed sequence of action effects, with randomly varying transformation rules. In the other group, the sequence of transformation rules was fixed, whereas the action effects were randomly varying. Results indicate that both kinds of sequences can be learned and provide evidence for the notion that transformation rules and action effects are represented separately.

Activation of action rules in action observation.

Visually perceiving an action may activate corresponding motor programs. This automatic motor activation can occur both for higher level (i.e., the goal of an action) and for lower level (i.e., the specific effector with which it is executed) aspects of an action. The authors used a tool-use action paradigm to experimentally dissociate priming effects for observing the target, the movement, or the target-to-movement mapping of a tool-use action. In 3 experiments, participants took turns in acting, observing the tool-use action of another person in trial n-1, and executing an action in trial n. Trial transitions from n-1 to n were manipulated in 4 conditions with (a) mapping repeated and movement and target changed, (b) target repeated and movement and mapping changed, (c) movement repeated and target and mapping changed, or (d) all components repeated. Results indicate priming effects for repeating the target-to-movement mapping (i.e., the action rule) of a tool-use action and suggest that a rather abstract action schema is activated during action observation.

Programming tool-use actions.

When humans plan to execute a tool-use action, they can only specify the bodily movement parameters by taking into account the external target or goal of the tool-use action and the target-movement mapping implemented by the tool. In this study, the authors used the movement precuing method to investigate how people prepare for actions made with tools. More specifically, they asked whether people would be able to specify the spatial target and the target-movement mapping of the tool-use action independently of each other, and to what degree they would be able to prepare these components in advance. In 3 experiments, they precued either the target or the target-movement mapping of tool-use actions involving either a compatible or an incompatible target-movement mapping. Results indicate that participants benefit from partial advance information about the target-movement mapping, whereas no significant effects were found for precuing the spatial target of the action. These results occurred regardless of whether the target-movement mapping was compatible or incompatible and provide evidence for the notion that the target-movement mapping of a tool-use action is part of its cognitive representation.

Inhibition of return impairs episodic memory access.

The term inhibition of return (IOR) refers to a bias against returning attention to a location or object that has recently been attended. The effect has been shown to occur in various perceptual tasks including stimulus detection, localization, and discrimination, but also to affect higher cognitive processes like lexical access. The present experiments examined whether inhibition of return would impair the high-level processing that is required in accessing item representations in episodic memory. The results show that reaction times for recognition memory decisions are increased under IOR. Furthermore, IOR affects the accuracy of recognition memory, and this effect interacts with the ease of memory access, manipulated, for example, by encoding depth in the learning phase. These results suggest that IOR impairs attentional processing up to the highest cognitive levels, including the access of prior item encounters in episodic memory.