- Email: [email protected]
Lateralized interference in finger tapping: Initial value differences do not affect the outcome
&wroprwholoqm Prmted ,n Great
Vol.
28. So.
3. pp
313-316.
1990
c
Brlta~n
0028-3932~90 $3.00+0 00 1990 Pergamon Pressplc
NOTE LATERALIZED INTERFERENCE IN FINGER DIFFERENCES DO NOT AFFECT
TAPPING: INITIAL VALUE THE OUTCOME
DANIEL W. KFE* and BARBARACHERRY
*Department
of Psychology,
California
State University,
Fullerton,
CA 92634, U.S.A
(Received 3 July 1989; accepted 13 October 1989) Ahstract--W1LL1s and GOODWIN, Neuropsychologia 25, 719-724, 1987, have suggested that asymmetric interference observed in dual-task/time-sharing studies may be a statistical artifact of “initial-values” differences and not hemispheric lateralization. In the present study lateralized fingertapping interference produced by concurrent anagram solution was observed even after the initial right-hand advantage in baseline tapping performance was removed experimentally.
INTRODUCTION DUAL-TAsK/time-sharing procedures have been used successfully to investigate the cerebral laterahzation of verbal processing in right-handed persons [l, 91. Typically this procedure requires subjects to perform a manual task such as finger tapping over a series of trials. On some trials finger tapping is performed alone, while on others the finger tapping is performed in conjunction with a verbal task such as paragraph reading [2, 33 or anagram solution [4.8]. When comparing the manual performance of the hands, the right hand is usually disrupted more than the left hand during the execution of the concurrent verbal task. This pattern of finger-tapping interference-greater right-hand than left-hand disruption-is usually interpreted to indicate left-hemisphere specialization for the verbal task because (a) the finger tapping of each hand is controlled primarily by the contralateral cerebral hemisphere and (b) two tasks should interfere with each other more if they are programmed by the same hemisphere rather than two different hemispheres [9]. Recently WILLS and GOODWIN [ 1l] have questioned interpretation of dual task outcomes: “A potential problem with analyzing raw scores generated through these paradigms is that they may be insensitive to lateralized interference effects. This is because research participants are usually right-handed and interhand comparisons of initial (i.e. baseline) tapping rates typically favor the right. Given this initial discrepancy between the hands, differential interference effects associated with the concurrent performance of an unrelated task may be due to initial differences in tapping speed rather than lateralization effects. In this respect, interference might be greater for right- than left-handed tapping because, due to the higher range of initial values for the right hand, there is a higher possible range for reduction” (p. 719). Their view suggests that the typical pattern of lateralized interference reported in dual-task studies may be a statistical artifact of hand differences in baseline-tapping performance. The present study provides an experimental assessment of this possibility. Right-handed subjects participated in the present study. The manual task was finger tapping and the verbal activity was anagram solution. Anagram solution has been reliably associated with lateralized finger-tapping interference in previous studies [4. 81. If lateralized finger-tapping interference is due solely to differences in initial values, this asymmetry effect should emerge only when the right-hand advantage-faster righthand than left-hand finger tapping-is present on baseline-tapping trials. However, if lateralized finger-tapping interference is observed regardless of whether the hands differ on baseline tapping trials, then the hemispheric specialization interpretation is bolstered. Thus, in the present study the finger-tapping task was arranged so that a comparison of lateralized interference was provided under two conditions: right-hand advantage present on baseline trials vs right-hand advantage absent on baseline trials.
*Author
to whom correspondence
should
be addressed. 313
314
NOTE
METHOD Manipulation
of the right-hand advantage on baseline trials
In our previous studies C&S] Micro Switch no. BA-2-V2-A2 has been used to record finger tapping and the righthand advantage in baseline performance had been observed. Thus. this tapping-key was used for both left- and righthand tapping in the standard condition of the present study. To adjust finger-tapping rate so that the right-hand advantage is removed a second Micro Switch no. BA-2-V2-A2 was used. The down-force for a switch closure and the travel release distance required were increased on this second switch. Thus. in the adjusted condition subjects used the standard switch for left-hand tapping and used the adjusted switch for right-hand tapping. The adjusted condition was designed to remove the right-hand advantage on baseline trials and a series ofcalibrations were used to determine the changes in down-force and travel release distance required to reduce right-hand performance down to the level of the left hand. The down-force and travel distance of the standard switch were 1.03 Newton (N) and 1.91 cm. respectively. Initially, informal calibrations were conducted with a small sample of subjects in which the down-force and travel release distance were systematically increased until the right-hand finger-tapping rate was equivalent to the lefthand finger-tapping rate. Force was adjusted by placing different weight springs beneath the switch lever. Travel release distance after a switch closure was adjusted by requiring subjects to lift their index finger to a reference bar positioned above the tapping key. After appropriate settings were identified by the informal calibration an independent sample of 10 right-handed subjects from our Introductory Psychology Subject Pool were tested to verify that the right-hand advantage was removed with the adjusted tapping key condition. The down-force and travel distance of the adjusted key used for the right hand were 3.38 N and 4.45 cm, respectively. The tapping keys were mounted 7 cm apart in a small (15 x 10 x 5.5 cm) metal box that was positioned at a comfortable distance from subjects in front of their right or left shoulders. A reference bar was stationed above the tapping keys and was attached to the ends of the box on vertical posts. The left key in the box was the standard switch, while the right key in the box was the adjusted switch. The keys were attached to an Apple II Plus computer with a Mountain Hardware msec clock card which timed 10 set tapping trials and recorded finger-tapping performance.
Design and subjects The experimental design was a two (sex: males and females) by two (tapping arrangement: standard vs adjusted) by two (condition: tapping alone vs tapping plus concurrent anagram solution) by two (hand: left vs right) by 2 (trials) factorial. With the exception of sex, all factors were manipulated within subjects. Trials for each tapping arrangement (standard vs adjusted) were blocked together and the order of testing for these trial blocks was counterbalanced across subjects. The order of condition (tapping alone vs tapping plus anagram solution) was counterbalanced within each block of standard vs adjusted trials. Half of the subjects started each condition with their right hand, while half began each condition with their left hand. Two trials of the same type were presented consecutively. Sixteen undergraduate students from the Introductory Psychology Subject Pool participated. Subjects were right-handed: confirmed by writing-hand inspection, right-hand advantage on baseline tapping trials with the standard-key arrangement, and Edinburgh Handedness Index [lo].
Materials
and procedures
Subjects were seated at a table and tested individually by a female experimenter in a quiet room. Subjects were informed that the experiment was designed to measure how fast they could tap during timed trials under various conditions. Subjects faced an opaque screen and a typing stand was positioned in front of the screen. For all tapping conditions subjects were told to tap as quickly as possible with the index finger. Practice was provided before the onset of each block of tapping trials (standard vs adjusted). A signal produced by the computer started and ended each 10 set trial. Recall that the standard condition used the unadjusted switch for both left- and right-hand tapping. In contrast, the adjusted condition used the unadjusted switch for the left hand, while the adjusted switch was used for the right hand. In the adjusted condition on right-hand tapping trials subjects were also told to release their finger and lift it to the reference bar after each switch closure. Anagrams were placed in front of the subjects on the typing stand just prior to the beginning of each anagram trial. Four single-solution anagrams were presented on each trial that required anagram solution. Eight lists of four anagrams were used and these lists were drawn from a larger set used in previous dual-task studies 14, 81. The anagrams had a low imagery rating and medium-to-high familiarity ratings (see [4] for details). The anagrams were arranged vertically and typed on 13 x 20 cm cards with an Orator 61-10 type size. Each anagram list appeared equally often across the factors of tapping hand, tapping arrangement and trial. Subjects were asked to solve the anagrams aloud on each trial and the number of anagrams solved correctly was recorded. When anagram solution was not required subjects were told to look at a 13 x 20 cm blank white-card set on the typing stand.
NOTE
315
RESULTS Hand difirences
in baseline rapping rate
Table 1 presents the baseline tapping rates. mean taps per sec. as a function of tapping arrangement (standard vs adjusted) and tapping hand. Analysis of variance revealed the following main effects: tapping was faster with the standard arrangement than the adjusted arrangement. F (1, 14)= 17.17: the right hand was faster than the left hand. F(l, 141=11.52. all PiO.01. One f t I. 14)= 17.43: and trial 1 (M=4.74) was faster than trial 2 (M=4.57). mteraction was observed: hand by tappingarrangement. F (1. 14)= 13.48. P
Table
I. Baseline performance: tapping
hand by tapping
Arrangement
Tapping Left
Standard Adjusted M
4.46 4.39 4.43
mean taps per set for arrangement hand Right 5.25 4.51 4.88
4.86 4.45
Dual-task .findiru~s variables of mean taps per set and percentage change in tapping rate were evaluated. The The dependent followine formula was used to calculate percentage change: [(T- TA)/Tj x 100 where Tis tapping performance in the tappmg only condition (baseline) and TA is tapping performance during concurrent anagram solutton. Analyses indrcated that both dependent measures led to the same conclusions about lateralized interference etTccts. Therefore onl! the results from the percentage change analysis will be reported. Table 2 presents the percentage change scores for the fxtors of tapping arrangement and hand. Analysis of variance revealed a main elTect of hand, F I 1. 14) = 18.46, P < 0.001. indicating that the right hand was disrupted more than the left by concurrent anagram solutton activity. This main effect was not qualified by a hand by tapping arrangement interaction, FC I. Thus. the asymmetrical interference-a pattern indicative of left-hemisphere specialization-obtains whether or not a righthand advantage is present in baseline performance. This outcome is incompatible with Willis and Goodwin’s suggestion that lateralized interference observed in dual-task studies are a statistical artifact of “initial values” differences in baseline tapping performance.
Table 2. Dual task performance: percentage change finger tapping for tapping hand by tapping arrangement
Arrangement Standard Adjusted M
Tapping Left -0.32 -0.57 0.45
hand Right 8.86 11.30 10.08
in
M 4.27 5.31
Only one other significant effect was found in the percentage-change analysis. A significant main effect for trials indicated more finger-tapping interference was observed on trial 1 (M=7.01) than trial 2 (M=2.54), F(1, 14)=8.66, P
Analysis of variance was conducted on the dependent variable of number of anagrams solved. No reliable differences weredctected. Theabsenceofa handeffect (left-M= 1.35;right-M= 1.22). F(I, 14)= 1.51,P>O.lO.ora hand by tapping arrangement interaction, F< 1. indicates that the lateralized finger-tapping interference observed cannot be attributed to an asymmetric trade-off with verbal-task performance.
316
NOTE
SUMMARY
AND CONCLUSIONS
Dual-task procedures have been used to estimate the hemispheric-specific involvement of various verbal tasks with right-handed subjects. Greater right--hand than left-hand finger-tapping disruption has been observed and this outcome has been interpreted to implicate left-hemisphere specialization. WILLIS and GOODWIN [I l] suggest that the asymmetrical interference may not represent a lateralization effect, but may be a statistical artifact of”initial value” differences in baseline-tapping performance. The results of the present study indicate that the presence of a right-hand advantage in baseline-tapping performance is neither a necessary nor a suficient condition for the detection of greater right-hand than left-hand finger-tapping interference. This finding diminishes the validity of the statistical artifact interpretation. Thus. the hemispheric specialization interpretation of lateralized finger-tappmg interference is sustained. This conclusion, however, does not imply that ali dual-task asymmetries in finger-tapping interference are due strictly to cerebra1 hemisphere specialization. For example, HELIXE and KEE [l] have recent]) suggested that both hemisphere-specific competition and hand dominance may contribute to the effect in some circumstances. Acknol~/~d~e,nenr-This Jones for his technical valuable comments.
research was supported by a grant from the CSUF Foundation. Gratitude IS extended to T. support. Appreciation is expressed to J. B. Hellige. M. O’Boyle and P. E. Worden for their
REFERENCES 1. HELLIGE. J. B. and KEE, D. W. Asymmetric Advances
in Psychology:
Cerebral
Conrrol
manual olspeech
interference
as an indicator
and Limb Movemenrs.
of lateralized
brain function. In North
G. R. HAMM~NV (Editor).
Holland, Amsterdam. in press. 2. HELLIGE. J. B. and LONGSTRETH, L. Effects of concurrent hemisphere-specific activity on unimanual tappmg rate. Neuropsychologia 19, 395405, 1981. 3. HIS~O~K, M., CHEESMAN,J., INCH, R., CHIPUER. H. M. and GRAFF. L. A. Rate and variability of finger tapping as measures of lateralized concurrent task effects. Brain Cognit. 10, 87-104. 1989. 4. KEE, D. W.. BATHURST. K. and HELLIGE. J. B. Lateralized interference of repetitivefinger tappmg: Intluence of familial handedness. cognitive load, and verbal production. Neurops?cko/ollia 21, 617-624..1983. 5. K~E, D. W.. BATHURST, K.. and HELLIGE. J. B. Lateralized interference in finger tappmp: Assessment of block _ ..design activities. Neuropsychologia 22, 197-203. 1984. 6. KEE. D. W.. MATTESON. R. and HELLIGE, J. B. Lateralized finger tapping interference produced by block design activities. Brain Cognit. 11, 127-132. 7. KEE, D. W.. GOTTFRIED, A., BATHURST, K. and BROWN, K. Left-hemisphere language specialization: Consistency in hand preference and sex differences. Child Deal. 58, 718-724. 1987. interference m finger tapping: 8. KEE. D. W.. MORRIS, K.. BATHURST, K. and HELLIGE. J. B. Lateralized Comparisons of rate and variability measures under speed and consistency tapping instructions. L(rai,r Co
Vol.
28. So.
3. pp
313-316.
1990
c
Brlta~n
0028-3932~90 $3.00+0 00 1990 Pergamon Pressplc
NOTE LATERALIZED INTERFERENCE IN FINGER DIFFERENCES DO NOT AFFECT
TAPPING: INITIAL VALUE THE OUTCOME
DANIEL W. KFE* and BARBARACHERRY
*Department
of Psychology,
California
State University,
Fullerton,
CA 92634, U.S.A
(Received 3 July 1989; accepted 13 October 1989) Ahstract--W1LL1s and GOODWIN, Neuropsychologia 25, 719-724, 1987, have suggested that asymmetric interference observed in dual-task/time-sharing studies may be a statistical artifact of “initial-values” differences and not hemispheric lateralization. In the present study lateralized fingertapping interference produced by concurrent anagram solution was observed even after the initial right-hand advantage in baseline tapping performance was removed experimentally.
INTRODUCTION DUAL-TAsK/time-sharing procedures have been used successfully to investigate the cerebral laterahzation of verbal processing in right-handed persons [l, 91. Typically this procedure requires subjects to perform a manual task such as finger tapping over a series of trials. On some trials finger tapping is performed alone, while on others the finger tapping is performed in conjunction with a verbal task such as paragraph reading [2, 33 or anagram solution [4.8]. When comparing the manual performance of the hands, the right hand is usually disrupted more than the left hand during the execution of the concurrent verbal task. This pattern of finger-tapping interference-greater right-hand than left-hand disruption-is usually interpreted to indicate left-hemisphere specialization for the verbal task because (a) the finger tapping of each hand is controlled primarily by the contralateral cerebral hemisphere and (b) two tasks should interfere with each other more if they are programmed by the same hemisphere rather than two different hemispheres [9]. Recently WILLS and GOODWIN [ 1l] have questioned interpretation of dual task outcomes: “A potential problem with analyzing raw scores generated through these paradigms is that they may be insensitive to lateralized interference effects. This is because research participants are usually right-handed and interhand comparisons of initial (i.e. baseline) tapping rates typically favor the right. Given this initial discrepancy between the hands, differential interference effects associated with the concurrent performance of an unrelated task may be due to initial differences in tapping speed rather than lateralization effects. In this respect, interference might be greater for right- than left-handed tapping because, due to the higher range of initial values for the right hand, there is a higher possible range for reduction” (p. 719). Their view suggests that the typical pattern of lateralized interference reported in dual-task studies may be a statistical artifact of hand differences in baseline-tapping performance. The present study provides an experimental assessment of this possibility. Right-handed subjects participated in the present study. The manual task was finger tapping and the verbal activity was anagram solution. Anagram solution has been reliably associated with lateralized finger-tapping interference in previous studies [4. 81. If lateralized finger-tapping interference is due solely to differences in initial values, this asymmetry effect should emerge only when the right-hand advantage-faster righthand than left-hand finger tapping-is present on baseline-tapping trials. However, if lateralized finger-tapping interference is observed regardless of whether the hands differ on baseline tapping trials, then the hemispheric specialization interpretation is bolstered. Thus, in the present study the finger-tapping task was arranged so that a comparison of lateralized interference was provided under two conditions: right-hand advantage present on baseline trials vs right-hand advantage absent on baseline trials.
*Author
to whom correspondence
should
be addressed. 313
314
NOTE
METHOD Manipulation
of the right-hand advantage on baseline trials
In our previous studies C&S] Micro Switch no. BA-2-V2-A2 has been used to record finger tapping and the righthand advantage in baseline performance had been observed. Thus. this tapping-key was used for both left- and righthand tapping in the standard condition of the present study. To adjust finger-tapping rate so that the right-hand advantage is removed a second Micro Switch no. BA-2-V2-A2 was used. The down-force for a switch closure and the travel release distance required were increased on this second switch. Thus. in the adjusted condition subjects used the standard switch for left-hand tapping and used the adjusted switch for right-hand tapping. The adjusted condition was designed to remove the right-hand advantage on baseline trials and a series ofcalibrations were used to determine the changes in down-force and travel release distance required to reduce right-hand performance down to the level of the left hand. The down-force and travel distance of the standard switch were 1.03 Newton (N) and 1.91 cm. respectively. Initially, informal calibrations were conducted with a small sample of subjects in which the down-force and travel release distance were systematically increased until the right-hand finger-tapping rate was equivalent to the lefthand finger-tapping rate. Force was adjusted by placing different weight springs beneath the switch lever. Travel release distance after a switch closure was adjusted by requiring subjects to lift their index finger to a reference bar positioned above the tapping key. After appropriate settings were identified by the informal calibration an independent sample of 10 right-handed subjects from our Introductory Psychology Subject Pool were tested to verify that the right-hand advantage was removed with the adjusted tapping key condition. The down-force and travel distance of the adjusted key used for the right hand were 3.38 N and 4.45 cm, respectively. The tapping keys were mounted 7 cm apart in a small (15 x 10 x 5.5 cm) metal box that was positioned at a comfortable distance from subjects in front of their right or left shoulders. A reference bar was stationed above the tapping keys and was attached to the ends of the box on vertical posts. The left key in the box was the standard switch, while the right key in the box was the adjusted switch. The keys were attached to an Apple II Plus computer with a Mountain Hardware msec clock card which timed 10 set tapping trials and recorded finger-tapping performance.
Design and subjects The experimental design was a two (sex: males and females) by two (tapping arrangement: standard vs adjusted) by two (condition: tapping alone vs tapping plus concurrent anagram solution) by two (hand: left vs right) by 2 (trials) factorial. With the exception of sex, all factors were manipulated within subjects. Trials for each tapping arrangement (standard vs adjusted) were blocked together and the order of testing for these trial blocks was counterbalanced across subjects. The order of condition (tapping alone vs tapping plus anagram solution) was counterbalanced within each block of standard vs adjusted trials. Half of the subjects started each condition with their right hand, while half began each condition with their left hand. Two trials of the same type were presented consecutively. Sixteen undergraduate students from the Introductory Psychology Subject Pool participated. Subjects were right-handed: confirmed by writing-hand inspection, right-hand advantage on baseline tapping trials with the standard-key arrangement, and Edinburgh Handedness Index [lo].
Materials
and procedures
Subjects were seated at a table and tested individually by a female experimenter in a quiet room. Subjects were informed that the experiment was designed to measure how fast they could tap during timed trials under various conditions. Subjects faced an opaque screen and a typing stand was positioned in front of the screen. For all tapping conditions subjects were told to tap as quickly as possible with the index finger. Practice was provided before the onset of each block of tapping trials (standard vs adjusted). A signal produced by the computer started and ended each 10 set trial. Recall that the standard condition used the unadjusted switch for both left- and right-hand tapping. In contrast, the adjusted condition used the unadjusted switch for the left hand, while the adjusted switch was used for the right hand. In the adjusted condition on right-hand tapping trials subjects were also told to release their finger and lift it to the reference bar after each switch closure. Anagrams were placed in front of the subjects on the typing stand just prior to the beginning of each anagram trial. Four single-solution anagrams were presented on each trial that required anagram solution. Eight lists of four anagrams were used and these lists were drawn from a larger set used in previous dual-task studies 14, 81. The anagrams had a low imagery rating and medium-to-high familiarity ratings (see [4] for details). The anagrams were arranged vertically and typed on 13 x 20 cm cards with an Orator 61-10 type size. Each anagram list appeared equally often across the factors of tapping hand, tapping arrangement and trial. Subjects were asked to solve the anagrams aloud on each trial and the number of anagrams solved correctly was recorded. When anagram solution was not required subjects were told to look at a 13 x 20 cm blank white-card set on the typing stand.
NOTE
315
RESULTS Hand difirences
in baseline rapping rate
Table 1 presents the baseline tapping rates. mean taps per sec. as a function of tapping arrangement (standard vs adjusted) and tapping hand. Analysis of variance revealed the following main effects: tapping was faster with the standard arrangement than the adjusted arrangement. F (1, 14)= 17.17: the right hand was faster than the left hand. F(l, 141=11.52. all PiO.01. One f t I. 14)= 17.43: and trial 1 (M=4.74) was faster than trial 2 (M=4.57). mteraction was observed: hand by tappingarrangement. F (1. 14)= 13.48. P
Table
I. Baseline performance: tapping
hand by tapping
Arrangement
Tapping Left
Standard Adjusted M
4.46 4.39 4.43
mean taps per set for arrangement hand Right 5.25 4.51 4.88
4.86 4.45
Dual-task .findiru~s variables of mean taps per set and percentage change in tapping rate were evaluated. The The dependent followine formula was used to calculate percentage change: [(T- TA)/Tj x 100 where Tis tapping performance in the tappmg only condition (baseline) and TA is tapping performance during concurrent anagram solutton. Analyses indrcated that both dependent measures led to the same conclusions about lateralized interference etTccts. Therefore onl! the results from the percentage change analysis will be reported. Table 2 presents the percentage change scores for the fxtors of tapping arrangement and hand. Analysis of variance revealed a main elTect of hand, F I 1. 14) = 18.46, P < 0.001. indicating that the right hand was disrupted more than the left by concurrent anagram solutton activity. This main effect was not qualified by a hand by tapping arrangement interaction, FC I. Thus. the asymmetrical interference-a pattern indicative of left-hemisphere specialization-obtains whether or not a righthand advantage is present in baseline performance. This outcome is incompatible with Willis and Goodwin’s suggestion that lateralized interference observed in dual-task studies are a statistical artifact of “initial values” differences in baseline tapping performance.
Table 2. Dual task performance: percentage change finger tapping for tapping hand by tapping arrangement
Arrangement Standard Adjusted M
Tapping Left -0.32 -0.57 0.45
hand Right 8.86 11.30 10.08
in
M 4.27 5.31
Only one other significant effect was found in the percentage-change analysis. A significant main effect for trials indicated more finger-tapping interference was observed on trial 1 (M=7.01) than trial 2 (M=2.54), F(1, 14)=8.66, P
Analysis of variance was conducted on the dependent variable of number of anagrams solved. No reliable differences weredctected. Theabsenceofa handeffect (left-M= 1.35;right-M= 1.22). F(I, 14)= 1.51,P>O.lO.ora hand by tapping arrangement interaction, F< 1. indicates that the lateralized finger-tapping interference observed cannot be attributed to an asymmetric trade-off with verbal-task performance.
316
NOTE
SUMMARY
AND CONCLUSIONS
Dual-task procedures have been used to estimate the hemispheric-specific involvement of various verbal tasks with right-handed subjects. Greater right--hand than left-hand finger-tapping disruption has been observed and this outcome has been interpreted to implicate left-hemisphere specialization. WILLIS and GOODWIN [I l] suggest that the asymmetrical interference may not represent a lateralization effect, but may be a statistical artifact of”initial value” differences in baseline-tapping performance. The results of the present study indicate that the presence of a right-hand advantage in baseline-tapping performance is neither a necessary nor a suficient condition for the detection of greater right-hand than left-hand finger-tapping interference. This finding diminishes the validity of the statistical artifact interpretation. Thus. the hemispheric specialization interpretation of lateralized finger-tappmg interference is sustained. This conclusion, however, does not imply that ali dual-task asymmetries in finger-tapping interference are due strictly to cerebra1 hemisphere specialization. For example, HELIXE and KEE [l] have recent]) suggested that both hemisphere-specific competition and hand dominance may contribute to the effect in some circumstances. Acknol~/~d~e,nenr-This Jones for his technical valuable comments.
research was supported by a grant from the CSUF Foundation. Gratitude IS extended to T. support. Appreciation is expressed to J. B. Hellige. M. O’Boyle and P. E. Worden for their
REFERENCES 1. HELLIGE. J. B. and KEE, D. W. Asymmetric Advances
in Psychology:
Cerebral
Conrrol
manual olspeech
interference
as an indicator
and Limb Movemenrs.
of lateralized
brain function. In North
G. R. HAMM~NV (Editor).
Holland, Amsterdam. in press. 2. HELLIGE. J. B. and LONGSTRETH, L. Effects of concurrent hemisphere-specific activity on unimanual tappmg rate. Neuropsychologia 19, 395405, 1981. 3. HIS~O~K, M., CHEESMAN,J., INCH, R., CHIPUER. H. M. and GRAFF. L. A. Rate and variability of finger tapping as measures of lateralized concurrent task effects. Brain Cognit. 10, 87-104. 1989. 4. KEE, D. W.. BATHURST. K. and HELLIGE. J. B. Lateralized interference of repetitivefinger tappmg: Intluence of familial handedness. cognitive load, and verbal production. Neurops?cko/ollia 21, 617-624..1983. 5. K~E, D. W.. BATHURST, K.. and HELLIGE. J. B. Lateralized interference in finger tappmp: Assessment of block _ ..design activities. Neuropsychologia 22, 197-203. 1984. 6. KEE. D. W.. MATTESON. R. and HELLIGE, J. B. Lateralized finger tapping interference produced by block design activities. Brain Cognit. 11, 127-132. 7. KEE, D. W.. GOTTFRIED, A., BATHURST, K. and BROWN, K. Left-hemisphere language specialization: Consistency in hand preference and sex differences. Child Deal. 58, 718-724. 1987. interference m finger tapping: 8. KEE. D. W.. MORRIS, K.. BATHURST, K. and HELLIGE. J. B. Lateralized Comparisons of rate and variability measures under speed and consistency tapping instructions. L(rai,r Co