What is crossed in crossed-hand effects?

Acta Psychologica 62 (1986) 89-100 North-Holland

89

WHAT IS CROSSED IN CROSSED-HAND EFFECTS? *

Lucia RIGGIO, Luiz de Gonzaga GAWRYSZEWSKI ** and Carlo UMILTA Universitb di Parma, Italy

Accepted August 1985

In choice RT tasks, when the subject crosses the hands two effects are observed: the direction of spatial compatibility reverses and response latency becomes overall longer. It has been proposed that the location of the response is compared to both its anatomical status (i.e., the hand that emits the response) and the location of the stimulus. When the hands are crossed, the former comparison yields the lengthening of RT while the latter yields the reversal in the direction of spatial compatibility. The present study aimed at testing the relative importance of two locational aspects of the response (i.e., the position of the effector and the position of the response goal) which were confounded in all previous studies. In both experiments the hands were always in anatomical uncrossed position but the position of the response goal might or might not be the same as that of the effector. In experiment 1 the responses were emitted by the index fingers, which were either uncrossed or crossed, whereas in experiment 2 the responses were emitted through two sticks, which again were either uncrossed or crossed. The results replicated both the reversal of spatial compatibility and the lengthening of RT. It was concluded that the effects of crossing the hands are due to the crossing of the response goals.

In choice reaction time (RT) tasks response latencies to right-side stimuli are shorter when emitted with the right than the left hand and vice versa for left-side stimuli. This is true irrespective of whether the location of the stimulus is predictive of the correct response (i.e., the condition is that of spatial compatibility; Simon 1969; Nicoletti et al. 1982) or the locational cue provided by the stimulus is irrelevant for

* The study was supported by funds from the Consiglio Nazionale delle Ricerche and the Minister0 della Pubblica Istruzione to Carlo Umilta. Luiz de Gonzaga Gawryszewski was postdoctoral fellow of CNPq-Brasil (proc. 200.049/82). The authors wish to thank Dr. A. Bullinger for helpful discussion of the experiments and Mr. G. Ianelli for writing and implement- ing the computer programs. ** Author’s present address: Universidade Federal Fluminense, Departamento de Neurobiologia, Niteroi, 24000 RI, Brasil.

Requests for reprints should be addressed to C. Umilta, Istituto di Fisiologia Umana, Universita di Parma, via Gramsci 14, 43100 Parma, Italy.

OOOl-6918/86/$3.50 0 1986, Elsevier Science Publishers B.V. (North-Holland)

90 L. Riggio et al. / Crossed-hand effects

selecting the response (i.e., the condition is that of the Simon effect; Simon 1969; Umilta and Nicoletti 1985).

The most convincing explanation of these effects is the one proposed by Wallace (1971) and recently elaborated upon by our group (see Nicoletti et al. 1982; Nicoletti and Umilta 1984; Nicoletti et al. 1984; Umilta and Nicoletti 1985). According to it, the positions of stimuli and responses are specified by binary spatial codes (Wallace 1971, 1972), which, in the horizontal dimension, are in terms of right and left with relation to some reference point. As shown by Nicoletti et al. (1982, 1984), the reference point is not one of the egocentric axes, such as the body midline, the head midline or the vertical retinal meridian: it is instead the location of the other stimulus or response that acts as the reference location according to which the position of the command stimulus and that of the required response, respectively, are coded as right or left.

In a choice RT task, when the position of the appropriate response is defined by the position of the stimulus, a translation from the spatial code of the stimulus to that of the response must take place (see Teichner and Krebs 1974). If the response set maps directly into the stimulus set, as happens when the right-side stimulus commands a right-side response and the left-side stimulus commands a left-side response, translational requirements are very low and stimulus-response (S-R) pairings are said to be compatible. By contrast, when different spatial codes are employed for stimuli and responses (i.e., the right-side stimulus commands a left-side response and vice versa) a certain amount of time is devoted to the transformation of the codes and S-R pairings are said to be incompatible. In other words, the degree of compatibility can be defined as ‘the proportion of choice reaction time that is attributable to stimulus-response translation time’ (Teichner and Krebs 1974: 91): the fewer the transformations required, the higher the degree of compatibility.

In essence, therefore, the coding hypothesis is based on the notion of the correspondence or noncorrespondence between the relative positional codes that define each S-R pairing. When a stimulus is presented, its spatial code relative to the position of the other stimulus is formed and compared to the spatial code of the response, also determined with relation to the position of the other response. Response latencies are faster when the two codes are the same than when they are different.

L. Riggio et al. / Crossed-hand effects 91

Two consequences result when subjects cross their hands so that the right hand is located to the left of the left hand and the left hand to the right of the right hand. The first is that spatial compatibility apparently reverses its direction. RT is now faster when the right-side stimulus signals a response with the hand located to the right even though this is the left hand, and vice versa for a left-side stimulus (Anzola et al. 1977; Brebner et al. 1972; Klapp et al. 1979; Nicoletti et al. 1982; Simon et al. 1970; Wallace 1971). It thus seems clear that compatibility depends on the encoding of the position of the response as opposed to the encoding of the responding hand (Nicoletti et al. 1982; Nicoletti et al. 1984; Wallace 1971). That is not to say that the responding hand is not coded. In fact, it can be argued (see below) that the other effect of crossing the hand is due to a conflict between the position of the response (e.g., on the right side) and its anatomical status (e.g., the left hand). Apart from that, it has been shown that compatibility depends on the anatomical status of the effector when positional cues are eliminated or rendered ineffective by an unusual body posture (Klapp et al. 1979; Ladavas and Moscovitch 1984).

The second consequence brought about by the crossing of the hands is that RT becomes overall longer than when the hands are in anatomical (uncrossed) position (Anzola et al. 1977; Klapp et al. 1979; Nico- letti et al. 1982; Nicoletti et al. 1984). Nicoletti et al. (1984) showed that the slowing down of RT with hands crossed is not due to bio-mechanical factors (i.e., an awkward posture; see Berlucchi et al. 1977; Klapp et al. 1979) and attributed it to a mismatch between the codes describing the relative position of the hand and the side of the body with which the hand is connected. With hands crossed a conflict would arise between two internal representations of the same effector, one locational and the other anatomical.

In summary, the coding explanation maintains that the location of the response is compared to both its anatomical status (Nicoletti et al. 1984) and the location of the stimulus (Nicoletti et al. 1982; Umilta and Nicoletti 1985). The outcome of the former comparison yields the lengthening of RT, whereas that of the latter yields the compatibility effect. It is thus clear that the coding of the location of the response is pivotal in determining compatible and incompatible relationships. What still needs to be clarified is what exactly is meant by ‘location of the response’.

In the case of a key-pressing response two locational aspects can be


distinguished (see also Guiard 1984; Klapp et al. 1979), that is the position of the effector (i.e., finger, hand, limb and the like) and position of the response goal (i.e., the key or the response apparatus in general). Wallace (1971) proposed that the subjects encoded the position of the effector and his suggestion was accepted in subsequent works (see, e.g., Nicoletti et al. 1982; Nicoletti et al. 1984) even though Brebner et al. (1972) instead stressed the importance of the position of the key. Both hypotheses seem warranted since in all previous studies the location of the effector coincided with that of the response goal. The following two experiments were therefore aimed at disentangling the relative contribution of these two factors (i.e., position of the effector and position of the response goal) in bringing about spatial compatibility.

In the two experiments the hands were always in anatomical (i.e., uncrossed) position but the location of the response goal might or might not be the same as that of the effector. In the first experiment the index fingers were either uncrossed or crossed while in the second the subjects operated two sticks, which again were either uncrossed or crossed. This way, in the uncrossed condition the effecters (the two hands) and the response goals (the two keys) occupied the same location in both absolute (i.e., in relation to the body midline) and relative (i.e., in relation to the other effector or response goal) terms. In the crossed condition the effecters and response goals occupied opposite locations, again either absolutely or relatively. Of course, the critical condition was the crossed one. It was reasoned that if the determining factor for spatial compatibility was the position of the effecters, the responses to stimuli presented on the same side of the hand should be faster than those to stimuli shown on the opposite side. By contrast, if the determining factor was the position of the response goal, the responses to stimuli shown on the side opposite to that of the hand should be faster than those to stimuli located on the same side. There is also the additional possibility that both factors (i.e., position of the effector and position of the response goal) play a role in spatial compatibility. As we have already pointed out (see Umilta and Nico- letti (1985) for a thorough discussion of this point) it is important to distinguish between those instances of compatibility in which the location of the stimulus signals the location of the appropriate key (spatial compatibility) from those in which the location of the stimulus is irrelevant to deciding which key to use in responding (the Simon


effect). The following experiments dealt exclusively with spatial compatibility and thus their results concern spatial compatibility only.

Experiments 1 and 2

Method

Subjects Thirty-two right-handed students at the University of Parma (aged 19-32 years)

served as paid subjects, 16 in each experiment. They had normal or corrected vision and were naive as to the purpose of the experiments. In experiment 1 all subjects were male, while in experiment 2, 8 were male and 8 female.

Apparatus The subject sat in front of a cathode-ray tube controlled by an Apple II computer.

The head was positioned in an adjustable head-and-chin rest, so that the distance between the eyes and the screen was approximately 50 cm. The stimuli (lo X lo in size and with a duration ranging from 100 to 150 msec) were shown 5’ on the right or left of a central fixation cross. The responses were emitted by pressing either of two keys of the computer keyboard (V and N). In experiment 1 the subjects depressed the keys directly by the index fingers, whereas in experiment 2 they used two plastic sticks. The computer was used for both generating the stimuli and recording response latencies and errors.

Procedure of experiment 1

There were two experimental sessions on consecutive days. The first was preceded by several informal practice trials and both were divided into 4 blocks separated by a 5-minute rest period. During each block (approximately 80 trials) the stimuli appeared according to a quasi-random sequence, which allowed a maximum of three consecutive presentations in the same visual field. Each trial began with the central cross that the subject fixated for 1 sec. Then a stimulus appeared to which the subject responded as fast as possible trying not to make errors. A visual feedback concerning speed and accuracy was given in the center of the screen. In one session the index fingers were uncrossed (i.e., the right finger depressed the right-side key and the left finger depressed the left-side key), while in the other session they were crossed (i.e., the right finger depressed the left-side key and the left finger depressed the right-side key). The hands were always in the anatomical uncrossed position, so that the right hand was on the right side and the left hand on the left side with relation to the body midline. The forearms rested on a layer of feathergum to allow a comfortable posture. In two blocks of each session, whether the indexes were crossed or not, the subject responded to the right-side stimulus by pressing the right-side key and to the left-side stimulus by pressing the left-side key (compatible condition). In the other two blocks the assign-


ment was reversed, so that the right-side stimulus required a response with the left-side key and the left-side stimulus required a response with the right-side key (incompatible condition). Half the subjects had the indexes uncrossed in the first session and crossed in the second while the remainder followed the opposite order. Similarly, half the subjects began with the compatible condition in the first session and with the incompatible condition in the second, while the sequence was reversed for the others. The instructions stressed both speed and accuracy. Trials for which RT was less than 150 msec or more than 1000 msec were considered errors. All types of errors were discarded and replaced.

Procedure of experiment 2

The procedure of experiment 2 replicated that of experiment 1 with the exception that the subjects responded by operating (with thumb, index finger and middle finger) two plastic sticks (15 cm in length and 0.6 cm in diameter) whose tips lay on the response keys. The position where the subjects had to keep their fingers (about 5 cm from the top end) <as clearly marked on the stick. In either the uncrossed or the crossed condition the whole hand was on one side in relation to the body midline (i.e., the right hand on the right side and the left hand on the left side). However, while in the uncrossed condition each hand depressed, by employing one of the sticks, the key located on its same side, in the crossed condition each hand responded through the key located on the opposite side. In other words, in the crossed condition only the sticks were crossed, not the hands nor the fingers (this latter happened in the crossed condition of experiment 1).

At this point a comparison between the response modes of the two experiments might be useful. For brevity we will consider only the responses to a right-side stimulus. In the uncrossed and compatible condition the subject had to depress the right-side key, by either the right index finger (experiment 1) or the stick held in the right hand (experiment 2). In the uncrossed and incompatible condition the correct key was that on the left side, which was operated by either the left index finger (experiment 1) or the stick held in the left hand (experiment 2). In the crossed and compatible condition the correct key was that on the right side and the subject depressed it by either the left index finger (experiment 1) or the stick held in the left hand (experiment 2). Finally, in the crossed and incompatible condition the right-side stimulus required a response with the left-side key, which was commanded by either the right index finger (experiment 1) or the stick held in the right hand (experiment 2).

Results and discussion

Experiment I The correct mean RTs and errors (arcsine transformed percentages) were entered

into two analyses of variance with three within-subject factors: hand (or finger; right or left), key (right or left) and stimulus (right or left).

For the errors, only the two-way interaction between key and stimulus was significant, P&15) = 17.98, p < 0.001. A post-hoc analysis with the Newman-Keuls method

Table 1


Mean RTs in milliseconds and standard deviations (in parentheses) for experiment 1

Responding hand Side of the response key Stimulus side

Right Left

Right

Left

Right 251(28) 315 (34) Left 348 (46) 305 (27)

Right 313 (28) 363 (47) Left 322 (34) 263 (37)

showed (both ps < 0.05) that in the incompatible condition there were more errors than in the compatible condition (4.8% and 4.5% for the right-left and left-right pairs vs 2.2% for the right-right pair and 2.3% for the left-left pair).

In the case of RTs, the hand main effect was significant, F(1,15) = 8.02, p < 0.02. The responses with the right hand (306 msec) were somewhat faster than those with the left (315 msec). This result is likely to be due to the fact that the subjects were right-handed. Of greater interest were two significant interactions. Key and stimulus interacted significantly, F&15) = 180.31, p < 0.001. For every subject the responses with the key located on the same side of the stimulus were faster than those emitted with the other key. This was true regardless of whether the fingers were crossed or not, that is regardless of the hand that operated the key (see table 1). For the right-side stimulus the responses with the right-side key were faster than those with the left-side key (285 msec vs 335 msec), whereas for the left-side stimulus the responses with the left-side key were faster than those with the right-side key (284 msec vs 339 msec). These differences were significant when tested with the Newman-Keuls method (both ps c 0.01). Key interacted significantly also with hand, F&15) = 65.07, p < 0.001, and all the subjects showed the effect. As confirmed by the post-hoc analysis (ps < 0.01 in both cases), the right-side key was depressed faster by the right than the left hand (286 msec vs 388 msec), whereas the opposite was true for the left-side key (292 msec vs 326 msec). In other words, responses with fingers crossed were slower than responses with fingers uncrossed. No other source was significant in either the RTs or the error analysis.

The two above interactions showed it is possible to replicate the effects obtained by crossing the hands without actually crossing them. The interaction between key and stimulus showed that what matters for spatial compatibility is the position of the key (response goal) not that of the hand (effector). Even though in the present experiment the index fingers, not the hands, were crossed the direction of the compatibility effect apparently reversed from the uncrossed to the crossed condition (see table 1). In the former, the right hand which operated the right-side key, responded faster to the right-side stimulus, whereas the left hand which operated the left-side key, was faster for the left-side stimulus. The compatibility effect was of 59 msec. When the fingers crossed, the right hand which now commanded the left-side key, was faster for the left-side stimulus, whereas the left hand which now commanded the right-side key, was


faster for the right-side stimulus. The reversed compatibility effect was of 47 msec. Of course, the two compatibility effects were in the same direction if, one considers the side of the key instead of the responding hand, as shown by the nonsignificant three-way interaction.

The interaction between hand and key showed an effect closely related to the slowing down of RT in the crossed-hand condition, which had been observed before. Here response latencies were 43 msec slower when the fingers were crossed than when they were uncrossed, despite the fact that the hands were always in anatomical position. It would seem therefore that the effect is attributable to a lack of congruence between the hand (effector) and the key (response goal).

Experiment 2 Also for this experiment mean correct RTs and errors (arcsine transformed per-

centages) were entered into two analyses of variance with three within-subject factors: Hand (or stick; right or left), key (right or left) and stimulus (right or left).

For errors, the interactions hand by key and key by stimulus were significant: F&15) = 6.32, p -C 0.025, and F(1,15) = 21.58, p < 0.001, respectively. Although not confirmed by the post-hoc comparisons, the right hand tended to be more accurate when using the right-side than the left-side key (1.5% vs 2.5% errors) and vice versa for the left hand (0.9% vs 2.3%). The post-hoc comparisons for the other interaction (both ps -C 0.05) confirmed that the right-side key was more accurate for the right-side than the left-side stimulus (1.1% vs 2.8% errors) and vice versa for the left-side key (0.9% vs 2.5%).

In the analysis for RTs two main effects were marginally significant, hand and stimulus: F&15) = 4.20, p -C 0.06, and F(1,15) = 6.45, p i 0.025, respectively. In 11 subjects out of 16 the right hand was faster than the left (336 msec vs 342 msec overall), which is not surprising since they were all right-handed. Because in the present experiment, as in the previous one, side of the stimulus coincided with field of stimulation, the finding of faster RT to the right-side than the left -side stimulus (again 336 msec vs 342 msec, the effect being present in 13 subjects) might be attributed to a propensity to orient attention towards the right visual field (see Umilta and Nicoletti 1985). In fact, also the advantage of the right hand over the left might be interpreted in attentional terms if one accepts the notion that people have the tendency to allocate attention to the dominant hand (see Rabbitt 1978).

The same two interactions that had proved significant in experiment 1 turned out to be significant in experiment 2, namely that between key and stimulus and that between hand and key: F&15) = 112.46, p ~0.001 and F(1,15) = 45.88, p < 0.001, respectively. Every subject showed both effects. Post-hoc pair-wise comparisons (both ps < 0.01) confirmed that the rigth-side key was faster for the right-side than the left-side stimulus (312 msec vs 369 msec) and vice versa for the left-side key (314 msec vs 360 msec). This was true irrespective of whether the sticks were uncrossed or crossed (see table 2). Similarly, the post-hoc analysis ( p s -C 0.01 in both cases) showed that the right hand was faster when it depressed (through its stick) the right-side than the left-side key (321 msec vs 364 msec), whereas the opposite was true of the left hand (311 msec vs 361 msec). No other source proved significant in either analysis of variance.


Table 2 Mean RTs in milliseconds and standard deviations (in parentheses) for experiment 2.

Responding hand Side of the response key Stimulus side

Right Left

Right Right 292 (39) 349 (45) Left 386 (52) 341 (43)

Left Right 332 (39) 389 (44) Left 335 (41) 288 (25)

Experiment 2 corroborated the main findings of experiment 1. The consequences of crossing the hands could be observed even when the hands were actually not crossed (see table 2). In the uncrossed condition the right hand, which operated the right-side key, was faster for the right-side stimulus, and the left hand, which operated the left-side key, was faster for the Ieft-side stimulus (a compatibility effect of 52 msec). By contrast, in the crossed condition the right hand, which now depressed the left-side key, was faster for the left-side stimulus, and the left hand, which depressed the right-side key, was faster for the right-side stimulus (a reversed compatibility effect of 51 msec). Of course, there was no reversal of the compatibility effect if one takes into consideration the key instead of the hand, as shown by the nonsignificant three-way interaction. In any event, as in experiment 1, the significant interaction between key and stimulus and the nonsignificant interaction between hand and stimulus demonstrated that the position of the key (i.e., the response goal) and not the position of the hand (i.e., the effector) was critical in bringing about spatial compatibility.

Also in this experiment responses with the sticks crossed were 46 msec slower than those with the sticks uncrossed. Note that the whole hand was always in anatomical uncrossed position and only the stick it held crossed the midline to reach the response key. Once again the slowing down of RT in the crossed condition appears to be attributable to a conflict between the hand (effector) and the key (response goal).

General discussion

It is known that in choice RT tasks the crossing of the hands gives rise to two distinct but related effects. The first is that the direction of spatial compatibility reverses, if one takes into consideration which hand emits the response. The second is that RT becomes overall slower.

Let us discuss the reversal of spatial compatibility first. Such reversal takes place because the right (left) hand, which, when the hands were uncrossed, had proved faster in responding to the right- (left-) side


stimulus, now is faster in-responding to the left- (right-) side stimulus (see, e.g., Anzola et al. 1977; Brebner et al. 1972; Nicoletti et al. 1982). The phenomenon becomes less surprising if one considers that in the uncrossed condition the right (left) hand operates the right- (left-) side key and thus emits a right- (left-) side response, whereas in the crossed condition the right (left) hand operates the left- (right-) side key and thus emits a left- (right-) side response. In other words, it seems that for spatial compatibility what matters is the congruence or incongruence of the spatial codes associated with the location of the stimulus and the location of the response (Brebner et al. 1972; Nicoletti et al. 1982; Nicoletti and Urnilta 1984). Such codes are formed with reference to the other stimulus or response not with reference to the body midline (Nicoletti et al. 1982; Nicoletti and Umilta 1984; Nicoletti et al. 1984). Only in circumstances where the locations of the two responses are difficult to discriminate the anatomical status of the response (i.e., which hand emits the response) plays a role in spatial compatibility (Klapp et al. 1979; Ladavas and Moscovitch 1984).

In this framework we wondered why spatial compatibility involves decisions concerning the location of the response, whereas decisions regarding which anatomical hand is to be used are immaterial. There are two possible ways to explain why locational but not anatomical relations are important in spatial compatibility. One suggests that the same hand is coded in two different ways depending on where it is located in relation to the other (note that Nicoletti et al. (1984) have shown that what matters is the relative position of the two effecters, not the hem&pace where they perform). For example, the right hand is the right-side effector in the uncrossed condition and becomes the left-side effector in the crossed condition. If this were true, then spatial compatibility would depend on a match or mismatch between the spatial code of the stimulus and the spatial code of the effector.

The other possibility is that what is coded is the location of the key or, more precisely, the location of the response goal. In other words, the right- (left-) side key would remain the right- (left-) side response goal irrespective of the hand that actually presses it. Thus spatial compatibility would depend on a match or a mismatch between the spatial code of the stimulus and the spatial code of the response goal.

In all previous studies effecters and response goals were confounded. That was not the case of the present experiments in which each effector (hand) had a response goal (key) that shared (uncrossed condition) or


did not share (crossed conditions) the same locational code. The results were clear in showing that spatial compatibility depended on the location of the response goal whereas the location of the effector had no effect whatsoever. Such result is even more striking if one considers that the subjects could render compatible (i.e., much easier) the incompatible crossed condition by coding the position of the hand instead of that of the key. For example, when the right-side stimulus was shown they had to press the left-side key through a movement performed by the right hand, which was located on the same side of the stimulus. Had the subjects considered only the position of the hand, the task would have become compatible because the right-side stimulus would have been paired to the right-side effector. Some realized that and reported trying to adopt this strategy. However, the results clearly showed that spatial compatibility was determined by the location of the response goal, which dominated over the location of the effector.

The second effect of crossing the hands is a general lengthening of response latencies. According to Nicoletti et al. (1984) the effect is due to the fact that when the hands are crossed there is a mismatch between the anatomical status of the effector (e.g., the right hand) and its relative position in relation to the other effector (e.g., the right hand has become the left-side effector). The present study showed that the hands need not be crossed in order for the effect to be present. In our crossed conditions the right (left) hand did not become the left- (right-) side effector, it simply operated the left- (right-) side key. Therefore, the cause of the lengthening of RT could be either the fact that the location of the effector and the location of the response goal did not coincide (e.g., the right-side effector had a left-side response goal) or the fact that the anatomical status of the effector did not match the side of the response goal (e.g., the right hand had a left-side response goal). The former explanation is unlikely in view of the observation that RTs were slower in the crossed condition also when, as was the case for all previous studies (see review in Nicoletti et al. (1984) and introduction above), the location of the effector and that of the response goal were the same. It would thus seem that in the crossed condition RT became slower because of a mismatch between the responding hand and the locus of the response goal. In other words, there seems to be a natural propensity for the hand connected with the right half of the body to act on the right side and for the hand connected with the left half of the body to act on the left side.


References

Anzola, G.P., G. Bertoloni, H.A. Buchtel and G. Rizzolatti, 1977. Spatial compatibility and anatomical factors in simple and choice reaction time. Neuropsychologia 15, 295-302.

Berlucchi, G., F. Crea, M. Di Stefano and G. Tassinari, 1977. Influence of spatial stimulus-response compatibility on reaction time of ipsilateral and contralateral hand to lateralized light stimuli. Journal of Experimental Psychology: Human Perception and Performance 3, 505-517.

Brebner, J., M. Shepard and P. Cairney, 1972. Spatial relationships and S-R compatibility. Acta Psychologica 36, l-15.

Guiard, Y., 1984. Spatial compatibility effects in the writing page: a comparison of left-handed inverters and noninverters. Acta Psychologica 57, 17-28.

Klapp, S.T., D.M. Greim, C.M. Mendicino and R.S. Koenig, 1979. Anatomic and environmental dimensions of stimulus-response compatibility: implication for theories of memory coding. Acta Psychologica 43, 367-379.

Ladavas, E. and M. Moscovitch, 1984. Must egocentric and environmental frames of reference be aligned to produce spatial S-R compatibility effects? Journal of Experimental Psychology: Human Perception and Performance 10, 205-215.

Nicoletti, R. and C. Umilta, 1984. Right-left prevalence in spatial compatibility. Perception& Psychophysics 35, 333-343.

Nicoletti, R., C. Umilta and E. Ladavas, 1984. Compatibility due to the coding of the relative position of the effecters. Acta Psychologica 57, 133-143.

Nicoletti, R., G.P. Anzola, G. Luppino, G. Rizzolatti and C. Umilta, 1982. Spatial compatibility effects on the same side of the body midline. Journal of Experimental Psychology: Human Perception and Performance 8, 664-673.

Rabbitt, P.M.A., 1978. Hand dominance, attention, and the choice between responses. Quarterly Journal of Experimental Psychology 30, 407-416.

Simon, J.R., 1969. Reactions towards the source of stimulation. Journal of Experimental Psy- chology 81, 174-176.

Simon, J.R., J.V. Hinrichs and J.L. Craft, 1970. Auditory S-R compatibility: reaction time as a function of ear-hand correspondence and ear-response-location correspondence. Journal of Experimental Psychology 86, 97-102.

Teichner, W.H. and M.J. Krebs, 1974. Laws of visual choice reaction time. Psychological Review 81, 75-98.

Umilta, C. and R. Nicoletti, 1985. ‘Attention and coding effects in S-R compatibility due to irrelevant spatial cues’. In: M.I. Posner and O.S.M. Marin (eds.), Mechanisms of attention: attention and performance XI. Hillsdale, NJ: Erlbaum. pp. 457-471.

Wallace, R.J., 1971. S-R compatibility and the idea of the response code. Journal of Experimental Psychology 88, 354-360.

Wallace, R.J., 1972. Spatial S-R compatibility effects involving kinesthetic cues. Journal of Experimental Psychology 93, 163-168.

What is crossed in crossed-hand effects?

Documents

Transcript of What is crossed in crossed-hand effects?