The ideomotor principle and motor sequence acquisition: Tone effects facilitate movement chunking

Participants practiced short sequences of key presses; sequence length and response-effect mapping were the independent variables. Contingent, distinct key-effect relations were contrasted with either contingent but uniform or no response effects. In Experiment 1, tone effects were relevant as response-specific stimuli and also as effects. The sequence length effect for the tones group was reduced. In Experiment 2, participants were informed about the sequences to be executed and then given varying amounts of preparation time before the start signal. A reduction in the sequence length effect was observed, and initiation times and mean interresponse time (IRTs) were generally reduced in the tone group. Preparation time could compensate for some but not all of the latency reducing influence of the tone effects. The results are discussed with reference to ideomotor approaches to motor control, i.e., the notion that actions are represented in sensory format.     

Effector dependent sequence learning in the serial RT task

At least five earlier studies could not find effector-dependent learning in the keying version of the serial reaction time (RT) task. Experiment 1 examined whether effector-dependent learning occurs when participants practice the serial RT task with three fingers of one hand for about 1,300 sequence repetitions instead of the more common 50-100 repetitions. The results confirm that, following extended practice, sequence learning produces an effector-dependent component. Specifically, an unpracticed hand executed a practiced sequence slower than a practiced hand. However, Experiment 2 showed that effector-dependent sequence learning develops only when fingers of one hand are used, suggesting that effector-dependent sequence learning involves adjustment to the mechanical interactions between the fingers of one hand. In addition, when sequences had been practiced with one hand, mirror versions of the practiced sequences in both experiments showed moderate transfer. But when practiced with two hands no transfer to a mirrored version of the sequence was observed. This suggests that only practice with one hand produces a representation that facilitates the execution of mirror sequences. Generally, the same results were found in more or less aware participants, congruent with the idea that the effector-dependent representation and the representation allowing transfer to mirror sequences are implicit.     

Vision of a pictorial hand modulates visual-tactile interactions

The participants in this study discriminated the position of tactile target stimuli presented at the tip or the base of the forefinger of one of the participants’ hands, while ignoring visual distractor stimuli. The visual distractor stimuli were presented from two circles on a display aligned with the tactile targets in Experiment 1 or orthogonal to them in Experiment 2. Tactile discrimination performance was slower and less accurate when the visual distractor stimuli were presented from incongruent locations relative to the tactile target stimuli (e.g., tactile target at the base of the finger with top visual distractor) highlighting a cross-modal congruency effect. We examined whether the presence and orientation of a simple line drawing of a hand, which was superimposed on the visual distractor stimuli, would modulate the cross-modal congruency effects. When the tactile targets and the visual distractors were spatially aligned, the modulatory effects of the hand picture were small (Experiment 1). However, when they were spatially misaligned, the effects were much larger, and the direction of the cross-modal congruency effects changed in accordance with the orientation of the picture of the hand, as if the hand picture corresponded to the participants’ own stimulated hand (Experiment 2). The results suggest that the two-dimensional picture of a hand can modulate processes maintaining our internal body representation. We also observed that the cross-modal congruency effects were influenced by the postures of the stimulated and the responding hands. These results reveal the complex nature of spatial interactions among vision, touch, and proprioception.     

Equivalence classes generated by sequence training

In Experiment 1, 3, adult females were taught with verbal instructions and contingencies to select, in sequence, three arbitrary visual stimuli from an array of five stimuli. After four different sequences were taught, match-to-sample tests assessed emergent conditional relations among all stimuli that had been selected in the same order in the sequences. Subjects' performances indicated development of four stimulus classes, three based on ordinal position and one based on nonselection. Next, match-to-sample training established conditional relations between each of four novel figures and one member of each of the ordinal stimulus classes. Tests confirmed that the classes were equivalence classes, each expanded by one new member. In subsequent sequence tests, the new stimuli were selected in a sequence that was consistent with ordinal class membership. Experiment 2 replicated Experiment 1 with 2 different adult females, but the verbal instructions were omitted. Results were similar to Experiment 1, except that extensive review and retesting were required before expansion of the ordinal classes with the novel figures was observed.     

Response stereotypy without automaticity: Not quite involuntary attention in the pigeon

Previous research has shown that when pigeons are required to peck each of two keys four times in any order for reinforcement, stereotyped response sequences develop, though they are not required by the task. However, despite this stereotypy, sequences are not automatized. They require sufficient attention that sequence performance is disrupted by a concurrent, delayed matching-to-sample task. In the present experiments, pigeons were required to execute response sequences and delayed matching-to-sample concurrently. Experiment 1 showed that the matching task disrupts sequence performance even when the matching sample stimuli do not have to be processed concurrently with sequence execution. The presence of sample stimuli during sequence execution seems to command attention even if the sample stimuli are also available for processing when sequences are not being executed. Experiment 2 used the directed forgetting technique to show that pigeons do seem able to ignore sample stimuli if they are given information that tells them they will not be required to remember those stimuli later. Together, the experiments suggest attentional mechanisms in the pigeon that are not quite involuntary.     

Independence of serial position and response conflict in pre-planned manual response sequences

The present study investigates the effect of spatial stimulus–response correspondence (i.e. Simon effect) in pre-planned manual response sequences. Participants performed pre-cued response sequences consisting of three (Experiment 1) or four (Experiments 2 and 3) key-presses at different locations. Importantly, participants performed each response to a visual go signal, which appeared at a location corresponding to one response in the sequence. This task allowed investigating interference gradients across spatially noncorresponding conditions. We observed a Simon effect at each serial position, that is, RT for the corresponding condition was always shorter than RT for each noncorresponding condition. However, we failed to observe interference gradients from both preceding and subsequent responses in the sequence. These results are inconsistent with (1) a primacy gradient of activations representing serial order and (2) the temporary suppression of an executed response as a mechanism for preventing response repetitions. However, results provide indirect evidence for positional models of serial order.     

Inter-manual transfer and practice: Coding of simple motor sequences

Previous research suggests that movements are represented early in practice in visual-spatial coordinates/codes, which are effector independent, and later in practice in motor coordinates/codes (e.g., joint angles, activation patterns), which are effector dependent. In the present experiments, the task was to reproduce 1.3 s patterns of elbow flexions and extensions. An inter-manual transfer paradigm was used in Experiment 1 and an inter-manual practice paradigm was used in Experiment 2. The present results clearly indicated a strong advantage of effector transfer when the motor coordinates available during acquisition were reinstated (Experiment 1) and demonstrate that inter-manual practice with the same motor coordinates results in enhanced retention performance relative to transfer and practice where the same visual-spatial coordinates are used. These results demonstrate that the more effective movement code (motor or visual-spatial) is dependent on the movement sequence characteristics (e.g., difficulty, number of elements, and mode of control [preplanned or on-line]). These results are also interesting because they indicate, contrary to previous findings with more complex movement sequences, that an effective motor code can be developed relatively early in practice for rapid movement sequences.     

Effect of sequence length on the execution of familiar keying sequences: lasting segmentation and preparation?

The author assessed the mechanisms underlying skilled production of keying sequences in the discrete sequence-production task by examining the effect of sequence length on mean element execution rate (i.e., the rate effect). To that end, participants (N = 9) practiced fixed movement sequences consisting of 2, 4, and 6 key presses for a total of 588 trials per sequence. In the subsequent test phase, the sequences were executed with and without a verbal short-term memory task in both simple and choice reaction time (RT) paradigms. The rate effect was obtained in the discrete sequence-production task-including the typical quadratic increase in sequence execution time (SET, which excludes RT) with sequence length. The rate effect resulted primarily from 6-key sequences that included 1 or 2 relatively slow elements at individually different serial positions. Slowing of the depression of the 2nd response key (R2) in the 2-key sequence reduced the rate effect in the memory task condition, and faster execution of the 1st few elements in each sequence amplified the rate effect in simple RT. Last, the time to respond to random cues increased with position, suggesting that the mechanisms that underlie the rate effect in new sequences and in familiar sequences are different. The data were in line with the notion that coding of longer keying sequences involves motor chunks for the individual sequence segments and information on how those motor chunks are to be concatenated.     

Interference Effects in Learning Similar Sequences of Discrete Movements

Three experiments were conducted to examine proactive and retroactive interference effects in learning 2 similar sequences of discrete movements. In each experiment, the participants in the experimental group practiced 2 movement sequences on consecutive days (1 on each day, order counterbalanced across participants) followed by retention tests on the third day. In all, 2 out of 8 target locations differed between the 2 sequences. Experiment 1 established the nature of the interference effects in the present setup. Clear evidence was found for button-specific proactive and retroactive interference effects. Experiments 2 and 3 further probed the mechanisms underlying those effects, by varying the numbers of repetitions (50 or 250) of the 1st and 2nd sequence (Experiment 2) and the hand, dominant or nondominant, with which the sequences were practiced (Experiment 3). Experiment 2 showed that after a mere 50 repetitions, the representation of the movement structure was strong enough to evoke the effects observed in Experiment 1. Experiment 3 revealed that learning with the dominant hand did not result in more pronounced interference effects compared with learning with the nondominant hand. In combination, these results suggest that changes in the representation of the movement structure are primarily responsible for the observed interference effects.     

Influences of hand posture and hand position on compatibility effects for up-down stimuli mapped to left-right responses: evidence for a hand referent hypothesis

Unimanual left-right responses to up-down stimuli show a stimulus-response compatibility (SRC) effect for which the preferred mapping varies as a function of response eccentricity. Responses made in the right hemispace and, to a lesser extent, at a midline position, are faster with the up-right/down-left mapping than with the up-left/down-right mapping, but responses made in the left hemispace are faster with the up-left/down-right mapping. Also, for responses at the midline position, the preferred mapping switches when the hand is placed in a supine posture instead of the more usual prone posture. The response eccentricity effect can be explained in terms of correspondence of asymmetrically coded stimulus and response features, but it is not obvious whether the hand posture effect can be explained in a similar manner. The present study tested the implications of a hypothesis that the body of the hand provides a frame of reference with respect to which the response switch is coded as left or right. As was predicted by this hand referent hypothesis, Experiment 1 showed that the influence of hand posture (prone and supine) on orthogonal SRC was additive with that of response location. In Experiment 2, the location of the switch relative to the hand was varied by having subjects use either a normal grip in which the switch was held between the thumb and the index finger or a grip in which it was held between the little and the ring fingers. The magnitudes of the mapping preferences varied as a function of the grip and hand posture in a manner consistent with the hand referent hypothesis.     

Stimulus-response compatibilities between vertically oriented stimuli and horizontally oriented responses: the effects of hand position and posture

Stimulus-response (S-R) compatibility effects between vertically oriented stimuli (above or below fixation) and horizontally oriented responses (left or right switch deflections by a single hand) have been shown to depend both on which hand responds (Bauer & Miller, 1982) and on the location at which the response is made (eccentricity on a frontoparallel line; Michaels, 1989). In the latter study, hand position and hand posture were confounded, so it is unclear which variable determined the compatibility effect. In Experiment 1, the importance of effector position was tested. Vertically oriented stimuli were paired with a horizontal response solicited at different locations but always involving the same hand posture. Compatibility effects emerged, and their direction depended on position. In Experiment 2, the compatibilities were not evident in a simple reaction time paradigm, so the effect was not due to differential ease of responses. In Experiment 3, a change in hand posture (palm up or palm down) at the same location (the body midline) also affected the compatibilities. It was concluded that the S-R compatibility of orthogonally oriented stimuli and responses is influenced by (1) which hand responds, (2) the location of that hand, and (3) its posture. The results imply that both postural and positional states of the action system affect S-R compatibility.     

Hand position as a variable determining the accuracy of aiming movements

Two experiments investigated the effect of hand position on the accuracy of short- and long-duration aiming movements in the presence and absence of visual feedback. In Experiment 1 (N = 16) short aiming movements were executed rapidly, which would require them to be predominantly programmed, whereas in Experiment 2(N = 8) these movements were performed slowly enough so that visual feedback, which implies that they were predominantly programmed. However, the long-duration, short-length movements of Experiment 2 were disrupted when visual feedback was removed, which suggests that these movements were being guided by visual feedback. Having the heel of the responding hand in contact with the target platform during the response resulted in greater accuracy than no hand contact for the short-length movements of both experiments. Taken together, these results indicated that hand contact produced greater aiming accuracy than no hand contact for both programmed- and feedback-based movements.     

Development of complex, stereotyped behavior in pigeons

A pigeon's peck on one key moved a light down one position in a 5×5 matrix of lights, while a peck on another key moved the light across one position. Reinforcement depended upon the occurrence of four pecks on each key (moving the matrix light from the top left to the bottom right), and a fifth peck on either key ended a trial without food. Though there were 70 different sequences that led to reinforcement, each of 12 pigeons developed a particular, stereotyped sequence which dominated its behavior (Experiment 1). Extinction produced substantial increases in sequence variability (Experiment 2). Removal of the matrix cues disrupted performance, though it partially recovered with extended training (Experiment 3). The pigeons did not master a contingency which required a different sequence on the current trial than on the previous one (Experiment 4), though they were able to learn to emit sequences which began with either left-left or left-right response patterns (Experiment 5). The experiments suggest that contingencies of reinforcement may contribute to the creation of complex units of behavior, and that stereotypy may be a likely consequence of contingent reinforcement.     

Stimulus-dependent modulation of perceptual and motor learning in a serial reaction time task

In two experiments, we investigated the impact of spatial attributes on the representation acquired during a serial reaction time task. Two sequences were used, in which structural regularities occurred either in the horizontal or in the vertical locations of successive stimuli. After training with the dominant hand, participants were required to respond with the non-dominant hand to either the original sequence or to a mirror-ordered version of the original sequence that required finger movements homologous to those used during training. We observed that a difference in reaction times between the two transfer conditions was smaller in the vertical sequence than in the horizontal sequence. This pattern of results was independent of whether three fingers (Experiment 1) were used or only one finger (Experiment 2) was used for responding. This result suggests that perceptual and motor learning mechanisms may be weighted differently depending on the context in which the stimulus is presented.     

Influence of hand position on the near effect in 3-D attention

Voluntary reorienting of attention in real depth situations is characterized by an attentional bias to locations nearer the viewer once attention is deployed to a spatially cued object in depth. Previously, this effect (initially referred to as the near effect) was attributed to access of a 3-D viewer-centered spatial representation for guiding attention in 3-D space. The aim of this study was to investigate whether the near effect could have been associated with the position of the response hand, which was always near the viewer in previous studies that investigated endogenous attentional shifts in real depth. In Experiment 1, the response hand was placed at either the near or far target depth in a depth-cuing task. Placing the response hand at the far target depth abolished the near effect, but failed to bias spatial attention to the far location. Experiment 2 showed that the response hand effect was not modulated by the presence of an additional (passive) hand, whereas Experiment 3 confirmed that attentional prioritization of the passive hand was not masked by the influence of the responding hand on spatial attention in Experiment 2. The pattern of results is most consistent with the idea that response preparation can modulate spatial attention within a 3-D viewer-centered spatial representation.     

Positional information in short-term memory: Relative or absolute?

Evidence suggests that short-term memory for serial order includes information about the positions of items in a sequence. This information is necessary to explain why substitution errors between sequences tend to maintain their position within a sequence. Previous demonstrations of such errors, however, have always used sequences of equal length. With sequences of different length, both transpositions between groups (Experiment 1) and intrusions between trials (Experiment 2) are shown to respect position relative to the end as well as to the start of a sequence. These results support models in which position is coded by start and end markers, but not models in which position is coded in temporal or absolute terms. Possible interpretations of an end marker are discussed.     

Memory for Movement in Blind Children

The author assessed the mechanisms underlying skilled production of keying sequences in the discrete sequence-production task by examining the effect of sequence length on mean element execution rate (i.e., the rate effect). To that end, participants (N = 9) practiced fixed movement sequences consisting of 2, 4, and 6 key presses for a total of 588 trials per sequence. In the subsequent test phase, the sequences were executed with and without a verbal short-term memory task in both simple and choice reaction time (RT) paradigms. The rate effect was obtained in the discrete sequence-production task—including the typical quadratic increase in sequence execution time (SET, which excludes RT) with sequence length. The rate effect resulted primarily from 6-key sequences that included 1 or 2 relatively slow elements at individually different serial positions. Slowing of the depression of the 2nd response key (R₂) in the 2-key sequence reduced the rate effect in the memory task condition, and faster execution of the 1st few elements in each sequence amplified the rate effect in simple RT. Last, the time to respond to random cues increased with position, suggesting that the mechanisms that underlie the rate effect in new sequences and in familiar sequences are different. The data were in line with the notion that coding of longer keying sequences involves motor chunks for the individual sequence segments and information on how those motor chunks are to be concatenated.     

The perceived position of the hand in space

This paper reports a series of experiments of the perceived position of the hand in egocentric space. The experiments focused on the bias in the proprioceptively perceived position of the hand at a series of locations spanning the midline from left to right. Perceived position was tested in a matching paradigm, in which subjects indicated the perceived position of a target, which could have been either a visual stimulus or their own fingertip, by placing the index finger of the other hand in the corresponding location on the other side of a fixed surface. Both the constant error, or bias, and the variable error, or consistency of matching attempts, were measured. Experiment 1 showed that (1) there is a far-left advantage in matching tasks, such that errors in perceived position are significantly lower in extreme-left positions than in extreme-right positions, and (2) there is a strong hand-bias effect in the absence of vision, such that the perceived positions of the left and right index fingertips held in the same actual target position in fact differ significantly. Experiments 2 and 3 demonstrated that this hand-bias effect is genuinely due to errors in the perceived position of the matched hand, and not to the attempt at matching it with the other hand. These results suggest that there is no unifying representation of egocentric, proprioceptive space. Rather, separate representations appear to be maintained for each effector. The bias of these representations may reflect the motor function of that effector.     

Effector-independent and effector-dependent learning in the discrete sequence production task

This study examined whether skill in the discrete sequence production task involves, apart from the typical effector-independent component, an effector-dependent component. To that end, 12 participants practiced two 5-key sequences, each for 1,060 trials. One group practiced with three fingers of one hand, the other group with three fingers of two hands. In a subsequent test phase, participants in both groups executed the same sequences and two new sequences with the hand configuration they had used during practice, and with the hand configuration of the other group. The results provide support for an effector-dependent component in that both groups performed the practiced sequences faster with the hand configuration they had used during practice than with the hand configuration that was new to them. In addition, the unpracticed hand configuration performed the practiced sequences faster than the new sequence, which demonstrated the effector-independent component.     

Simple movement imitation: Are kinematic features sufficient to map perceptions into actions?

The aim of this study was to pinpoint the nature of the visual features used in the automatic mapping of perceived movements into similar executed movements, following the direct matching hypothesis. In Experiment 1 subjects imitated the lifting of one of two fingers, presented with different orientations. As predicted, stimuli which were further rotated away from the posture of the executing hand elicited slower reaction times. In Experiment 2, we verified that this orientation effect was not a purely perceptual effect by presenting the same stimuli but asking subjects to respond verbally. No orientation effect was found using a verbal response. In Experiment 3, we replaced the moving fingers by two arbitrary objects moving with the trajectories of the finger tips of Experiment 1. The same orientation effect as in Experiment 1 was observed. We conclude that in this experiment participants are using purely kinematic features to map perceived into executed movements.