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The laterality effect in reaction time to speech stimuli
Neuropsyclmlogia,1976,Vol. 14.pp. 14110 143.PcrgamonPmas.printedin England.
NOTE THE LATERALITY
EFFECT IN REACTION JACK CATLIN and
Department
TIME TO SPEECH STIMULI
HELEN NEVILLE
of Psychology, Cornell University, Ithaca, New York, 14850, U.S.A. (Received 27 February 1975)
Abstract-The difference favoring the right ear, in vocal reaction time to speech stimuli, does not appear to be smaller for stimuli presented strictly monaurally than for stimuli opposed by contralateral noise.
INTRODUCTION SPRINGER [l] has found a right-ear advantage for reaction time (RT) to speech stimuli, with speech presented to only one ear on each trial. She presented right-handed Ss with monosyllabic stimuli in one ear, and competing noise in the other. S’s task was to indicate, with a response of the right hand, whether or not the item uresented was a ore-snecified target. She found an overall RT difference in favor of the right ear. This e&t is presumably due to the slower transmission of left-ear information to left-hemisphere l&uage areas. The study reported in the present note was designed to clarify the nature of the RT laterality effect in two respects. First, can we obtain the effect using a vocal response? Is the effect independent of specit?c response mechanisms? SPRINGER [l] demonstrated the effect using a manual response. Second, is the RT laterality effect in fact a consequence of the competing noise? SPRINGER [l] wished to attribute the ditTerence she obtained to the presence of competing noise, but she did not run her Ss on a control condition without the competing noise (i.e., a monaural condition).* Thus, using a vocal response and a within-S design, we collected data on RT differences between the ears under both the competing-noise (CN) condition and the monaural (M) condition.
METHOD Subjects Ss were 12 members of the Cornell community (3 men, 9 women), paid for their services. Their ages ranged from 16 to 22 yr. All Ss were right-handed by the criteria of (1) no left-handed preference on the Edinburgh Handedness Inventory (OLDFTELD[2]), and (2) right-hand superiority on the manualdexterity tests of SKIZ, ACHENBAM, and FENNELL[3]. No Shad any personal history indicative of brain damage; by audiometric test, all had normal hearing. Apparatus Stimulus tapes were pm-recorded by a trained phonetician in a sound-attenuated room, using a Revox A77 tape recorder and a Sony ECM-21 microphone. The speech stimuli were the 25 monosyllabic letters of the alphabet (i.e., omitting “w”). These were recorded in eight different random orders, to a target dB level f3 dB. The experiment was run in a sound-attenuated room. In the experimental set-up, the output of the Revox fed into a Schmitt trigger. When a stimulus item was played, the Schmitt trigger gated on a voltage-controlled amnlifier, which then fed the stimulus item to one earsneaker of a matched set of Permoflux PDR-8 earphones: Where applicable, the amplifier simultaneously fed white noise to the other eampeaker. Thus, noise bursts, when used, began simultaneously with the speech, and had the same duration. Both speech and noise were presented at 80 dB re 0+002 dynes/cm*. * In a footnote, SPRINGER [l] did report a small monaural test, which found no RT laterality effect. However, in subsequent research with a manual response, and a within-S design (in preparation), we have found comparable effects under competing-noise and monaural conditions, in support of the results presented here. 141
142
Non?
The onset of each stimulus item also started a millisecond timer. S’s vocal response was picked up by a microphone which then stopped the timer, through a second Schmitt trigger. Procedure Conditions of presentation were: monaural, with speech to the right (M/R) or to the left ear (M/L); competing-noise, with speech to the right ear (CN/R) or to the left (CNJL). (Earphones were switched so that speech was always presented through the same earspeaker, regardless of ear of presentation.) In each condition, S’s task was to rapidly say the letter-name presented. Each S served in six sessions, usually on successive days; no successive sessions were separated by more than 2 days. In each session eight blocks of 25 trials were presented, two blocks for each condition. The inter-trial interval was 10 set, during which s’s RT and accuracy of vocal response were recorded. Blocks were separated by 1 min, except for a 10 min break in the middle. Each condition (M/R, M/L, CN/R, CN/L) occurred once in each half-session; no condition was used in two successive blocks. S was told the condition to be used before each block. Conditions were counterbalanced across sessions and 5s; stimulus tapes were counter-balanced across conditions, sessions, and 5s. Analysis The mean RT was calculated for each S for each condition for each session. In these calculations, the RT for any error trial was omitted, as were the RTs for the trials involving the same letter-name, in the other conditions, in the half-session in which S made the error. Statistical analyses (analysis of variance, and two-tailed t-tests) were based on the resulting mean RTs.
RESULTS Each mean RT value was calculated from the data to the nearest O-01 msec, and then rounded off to the value presented. Error rates Averaged across Ss and sessions, the error rates were l-3 % in the CN/R condition, 1.4% in CN/L, 1.0% in M/R, and 1.0% in Mb. The higher error rate in condition CN was sign&ant; t = 246.11 df, P < 0.05. RT laterality effect RT was faster for speech stimuli presented to the right ear. Averaged across Ss, sessions, and conditions (CN, Ivl). the mean RT for stimuli to the right ear was 444-9 msec; left ear, 4528 msec. The difference favoring the right ear was 7-9 msec; F = 6.56, 1 and 11 dA P < 0.03; Consider now this effect senaratelv for CN vs M conditions. The mean RT in condition CNlR was 436.1 msec; for condition CN/‘L, 445:O msec. The difference favoring the right ear was 90 msec; t E 2.72, 11 df, P = o-02. The mean RT in condition M/R was 453.8 mseci for condition M/L, 460.5 msec. The difference favoring the riaht ear was 6.7 msec: t = 2.12. 11 df. P = 04l6. The difference in the size of the RT laterality effec? in theCN condition versus in the M’condition was not significant; F = 1.13, 1 and 11 df, P > O-30. Effect of noise Averaged across ear of presentation, Ss, and sessions, the mean RT was 440-5 msec in the presence of competing noise, and 4571 msec in its absence. The difference favoring the CN condition was 16.6 msec; F = 27.13, 1 and 11 df, P < O-0005. For the right ear alone, the difference was 17.7 msec; r = 4-71, 11 df, P < O-001. For the left ear, the difference was 15.5 msec; t = 5.38, 11 df, P < @OOl.
DISCUSSION We have replicated SPRINGER’S[l] demonstration of an RT laterality effect, using a vocal rather than a manual response. Thus, the RT laterality effect can be assumed to be independent of specific response mechanisms, and can be attributed to the speech-processing system. Our data would not lead one to believe that the effect is due to the presence of competing noise; we found no reliable difference in size of RT laterality effect for M vs CN conditions. If the tinding of comparable differences for M and CN conditions is upheld, then SPRINGER’S[1] account of the RT laterality effect will have to be rejected. A more plausible conjecture about the basis of the effect would be that, in normal Ss who are left-hemisphere dominant for language, the functional pathway for left-ear speech information is first to the right hemisphere by way of the contralateral auditory pathway, and then across the corpus callosum to lefthemisphere language areas, even under strictly monaural conditions of presentation. (For the right ear, the functional pathway is the contralateral route directly to the left hemisphere.) This conjecture, that left-ear speech information follows the contralateral rather than the ipsilateral pathway even with monaural presentation, has previously been suggested by Bevw [4]; it is compatible with
NOTE
143
both his data and ours. Furthermore, in patients with right temporal-lobe lesions, there is a reduction intelligibility for material presented monaurally to the left ear (Bocca and CALEARO[A).
of
REFERENCES 1. SPRINGER,S. P. Hemispheric
2. 3. 4. 5.
specialization for speech opposed by contralateral noise. Percepfion and Psychophysics 13, 391-393, 1973. OLDFIELD,R. C. The assessment and analysis of handedness: The Edinburgh inventory. Neuropsychoiogia9, 97-113. 1971. SATZ, P., ACHENBACH.K. and FENN~LL, E. Correlations between assessed manual laterality and predicted speech laterality in a normal population. Neuropsychologia 5, 295-310, 1967. BEVER,T. G. The nature of cerebral dominance in speech behaviour of the child and adult. In Lcsguuge Acquisition: Models and Methods, R. HUXLEYand E. INGRAM (Editors), 231-261. Academic Press, New York, 1971. BO~CA,E. and CALEARO,C. Central hearing processes. In Modern Developments in Audiology, J. JERGER (Editor), 337-370. Academic Press, New York, 1963.
La difference reaction vocaleaux
le temps de
en faveur de l'oreille droite dam
stimulus de langage n’apparaft
pour les stimulus pr&sent&
en condition monaurale
pas &re
plus petite
stricte que pour
ceux auquel est oppose un bruit controlathal.
ZusaWoenfnssung Der
Unterschied
Reaktionszeiten
zugunsten auf
desrechten
sprachliche
Stimuli
Ohres
bei
scheint
zu sein fiir Stimuli, die strikt mono-aural
vokalen nicht
als fiir solche Stimuli, denen ein kontralaterales entgegengesetzt
wird.
kleiner
gegeben werden, Gerdusch
NOTE THE LATERALITY
EFFECT IN REACTION JACK CATLIN and
Department
TIME TO SPEECH STIMULI
HELEN NEVILLE
of Psychology, Cornell University, Ithaca, New York, 14850, U.S.A. (Received 27 February 1975)
Abstract-The difference favoring the right ear, in vocal reaction time to speech stimuli, does not appear to be smaller for stimuli presented strictly monaurally than for stimuli opposed by contralateral noise.
INTRODUCTION SPRINGER [l] has found a right-ear advantage for reaction time (RT) to speech stimuli, with speech presented to only one ear on each trial. She presented right-handed Ss with monosyllabic stimuli in one ear, and competing noise in the other. S’s task was to indicate, with a response of the right hand, whether or not the item uresented was a ore-snecified target. She found an overall RT difference in favor of the right ear. This e&t is presumably due to the slower transmission of left-ear information to left-hemisphere l&uage areas. The study reported in the present note was designed to clarify the nature of the RT laterality effect in two respects. First, can we obtain the effect using a vocal response? Is the effect independent of specit?c response mechanisms? SPRINGER [l] demonstrated the effect using a manual response. Second, is the RT laterality effect in fact a consequence of the competing noise? SPRINGER [l] wished to attribute the ditTerence she obtained to the presence of competing noise, but she did not run her Ss on a control condition without the competing noise (i.e., a monaural condition).* Thus, using a vocal response and a within-S design, we collected data on RT differences between the ears under both the competing-noise (CN) condition and the monaural (M) condition.
METHOD Subjects Ss were 12 members of the Cornell community (3 men, 9 women), paid for their services. Their ages ranged from 16 to 22 yr. All Ss were right-handed by the criteria of (1) no left-handed preference on the Edinburgh Handedness Inventory (OLDFTELD[2]), and (2) right-hand superiority on the manualdexterity tests of SKIZ, ACHENBAM, and FENNELL[3]. No Shad any personal history indicative of brain damage; by audiometric test, all had normal hearing. Apparatus Stimulus tapes were pm-recorded by a trained phonetician in a sound-attenuated room, using a Revox A77 tape recorder and a Sony ECM-21 microphone. The speech stimuli were the 25 monosyllabic letters of the alphabet (i.e., omitting “w”). These were recorded in eight different random orders, to a target dB level f3 dB. The experiment was run in a sound-attenuated room. In the experimental set-up, the output of the Revox fed into a Schmitt trigger. When a stimulus item was played, the Schmitt trigger gated on a voltage-controlled amnlifier, which then fed the stimulus item to one earsneaker of a matched set of Permoflux PDR-8 earphones: Where applicable, the amplifier simultaneously fed white noise to the other eampeaker. Thus, noise bursts, when used, began simultaneously with the speech, and had the same duration. Both speech and noise were presented at 80 dB re 0+002 dynes/cm*. * In a footnote, SPRINGER [l] did report a small monaural test, which found no RT laterality effect. However, in subsequent research with a manual response, and a within-S design (in preparation), we have found comparable effects under competing-noise and monaural conditions, in support of the results presented here. 141
142
Non?
The onset of each stimulus item also started a millisecond timer. S’s vocal response was picked up by a microphone which then stopped the timer, through a second Schmitt trigger. Procedure Conditions of presentation were: monaural, with speech to the right (M/R) or to the left ear (M/L); competing-noise, with speech to the right ear (CN/R) or to the left (CNJL). (Earphones were switched so that speech was always presented through the same earspeaker, regardless of ear of presentation.) In each condition, S’s task was to rapidly say the letter-name presented. Each S served in six sessions, usually on successive days; no successive sessions were separated by more than 2 days. In each session eight blocks of 25 trials were presented, two blocks for each condition. The inter-trial interval was 10 set, during which s’s RT and accuracy of vocal response were recorded. Blocks were separated by 1 min, except for a 10 min break in the middle. Each condition (M/R, M/L, CN/R, CN/L) occurred once in each half-session; no condition was used in two successive blocks. S was told the condition to be used before each block. Conditions were counterbalanced across sessions and 5s; stimulus tapes were counter-balanced across conditions, sessions, and 5s. Analysis The mean RT was calculated for each S for each condition for each session. In these calculations, the RT for any error trial was omitted, as were the RTs for the trials involving the same letter-name, in the other conditions, in the half-session in which S made the error. Statistical analyses (analysis of variance, and two-tailed t-tests) were based on the resulting mean RTs.
RESULTS Each mean RT value was calculated from the data to the nearest O-01 msec, and then rounded off to the value presented. Error rates Averaged across Ss and sessions, the error rates were l-3 % in the CN/R condition, 1.4% in CN/L, 1.0% in M/R, and 1.0% in Mb. The higher error rate in condition CN was sign&ant; t = 246.11 df, P < 0.05. RT laterality effect RT was faster for speech stimuli presented to the right ear. Averaged across Ss, sessions, and conditions (CN, Ivl). the mean RT for stimuli to the right ear was 444-9 msec; left ear, 4528 msec. The difference favoring the right ear was 7-9 msec; F = 6.56, 1 and 11 dA P < 0.03; Consider now this effect senaratelv for CN vs M conditions. The mean RT in condition CNlR was 436.1 msec; for condition CN/‘L, 445:O msec. The difference favoring the right ear was 90 msec; t E 2.72, 11 df, P = o-02. The mean RT in condition M/R was 453.8 mseci for condition M/L, 460.5 msec. The difference favoring the riaht ear was 6.7 msec: t = 2.12. 11 df. P = 04l6. The difference in the size of the RT laterality effec? in theCN condition versus in the M’condition was not significant; F = 1.13, 1 and 11 df, P > O-30. Effect of noise Averaged across ear of presentation, Ss, and sessions, the mean RT was 440-5 msec in the presence of competing noise, and 4571 msec in its absence. The difference favoring the CN condition was 16.6 msec; F = 27.13, 1 and 11 df, P < O-0005. For the right ear alone, the difference was 17.7 msec; r = 4-71, 11 df, P < O-001. For the left ear, the difference was 15.5 msec; t = 5.38, 11 df, P < @OOl.
DISCUSSION We have replicated SPRINGER’S[l] demonstration of an RT laterality effect, using a vocal rather than a manual response. Thus, the RT laterality effect can be assumed to be independent of specific response mechanisms, and can be attributed to the speech-processing system. Our data would not lead one to believe that the effect is due to the presence of competing noise; we found no reliable difference in size of RT laterality effect for M vs CN conditions. If the tinding of comparable differences for M and CN conditions is upheld, then SPRINGER’S[1] account of the RT laterality effect will have to be rejected. A more plausible conjecture about the basis of the effect would be that, in normal Ss who are left-hemisphere dominant for language, the functional pathway for left-ear speech information is first to the right hemisphere by way of the contralateral auditory pathway, and then across the corpus callosum to lefthemisphere language areas, even under strictly monaural conditions of presentation. (For the right ear, the functional pathway is the contralateral route directly to the left hemisphere.) This conjecture, that left-ear speech information follows the contralateral rather than the ipsilateral pathway even with monaural presentation, has previously been suggested by Bevw [4]; it is compatible with
NOTE
143
both his data and ours. Furthermore, in patients with right temporal-lobe lesions, there is a reduction intelligibility for material presented monaurally to the left ear (Bocca and CALEARO[A).
of
REFERENCES 1. SPRINGER,S. P. Hemispheric
2. 3. 4. 5.
specialization for speech opposed by contralateral noise. Percepfion and Psychophysics 13, 391-393, 1973. OLDFIELD,R. C. The assessment and analysis of handedness: The Edinburgh inventory. Neuropsychoiogia9, 97-113. 1971. SATZ, P., ACHENBACH.K. and FENN~LL, E. Correlations between assessed manual laterality and predicted speech laterality in a normal population. Neuropsychologia 5, 295-310, 1967. BEVER,T. G. The nature of cerebral dominance in speech behaviour of the child and adult. In Lcsguuge Acquisition: Models and Methods, R. HUXLEYand E. INGRAM (Editors), 231-261. Academic Press, New York, 1971. BO~CA,E. and CALEARO,C. Central hearing processes. In Modern Developments in Audiology, J. JERGER (Editor), 337-370. Academic Press, New York, 1963.
La difference reaction vocaleaux
le temps de
en faveur de l'oreille droite dam
stimulus de langage n’apparaft
pour les stimulus pr&sent&
en condition monaurale
pas &re
plus petite
stricte que pour
ceux auquel est oppose un bruit controlathal.
ZusaWoenfnssung Der
Unterschied
Reaktionszeiten
zugunsten auf
desrechten
sprachliche
Stimuli
Ohres
bei
scheint
zu sein fiir Stimuli, die strikt mono-aural
vokalen nicht
als fiir solche Stimuli, denen ein kontralaterales entgegengesetzt
wird.
kleiner
gegeben werden, Gerdusch