Impaired categorical perception of lexical tones in Mandarin-speaking congenital amusics

13 Pages·2012·0.32 MB·English

MemCogn(2012)40:1109–1121
DOI10.3758/s13421-012-0208-2
Impaired categorical perception of lexical tones
in Mandarin-speaking congenital amusics
CunmeiJiang&Jeff P. Hamm&Vanessa K. Lim&
Ian J. Kirk&Yufang Yang
Publishedonline:2May2012
#PsychonomicSociety,Inc.2012
Abstract The degree to which cognitive resources are Keywords Congenitalamusia .Mandarintone .Categorical
shared in the processing of musical pitch and lexical tones perception .Identification .Pitchdiscrimination
remains uncertain. Testing Mandarin amusics on their cate-
gorical perception of Mandarin lexical tones may provide
insight into this issue. In the present study, a group of 15 Musicandlanguageappearineveryhumansociety(Ayotte,
amusic Mandarin speakers identified and discriminated Peretz&Hyde,2002;Patel,2008),andbothappeartohave
Mandarin tones presented as continua in separate blocks. developed very early in human history. The oldest known
Thetonalcontinuaemployedwerefromahigh-leveltoneto musical instrument, a flute, dates to over 35,000 years ago
amid-risingtoneandfromahigh-leveltonetoahigh-falling (Conard, Malina & Münzel, 2009), and language has been
tone. The two tonal continua were made in the contexts of suggested to predate the African exodus (Atkinson, 2011).
naturalspeechandofnonlinguisticanalogues.Incontrastto The comparison between music and speech processing has
the controls, the participants with amusia showed no attracted much attention in recent years. On the basis of
improvement for discrimination pairs that crossed the music-relateddeficitsinbrain-damagedpatients,ithasbeen
classification boundary for either speech or nonlinguistic suggested that music and language may be processed in
analogues, indicating a lack of categorical perception. separate systems (Peretz, 2006; Peretz & Coltheart, 2003;
The lack of categorical perception of Mandarin tones in Peretz&Morais,1989),althoughspeakingandsingingmay
theamusicgroupshowsthatthepitchdeficitsinamusicsmay overlap(Peretz,2009).Alternatively,othershavesuggested
be domain-general, and this suggests that the processing of thatmusicandlanguageshareneuralresources,onthebasis
musical pitch and lexical tones may share certain cognitive of evidence derived from healthy individuals (Patel, 2003,
resourcesand/orprocesses(Patel2003,2008,2012). 2008, 2012). The latter, resource-sharing framework posits
that although language and music involve domain-specific
representations, similar cognitive operations that share
C.Jiang neural resources are conducted on these domain-specific
MusicCollege,ShanghaiNormalUniversity, representations (Patel, 2012). For example, pitch is a vital
100E.GuilinRoad,
element in both tonal music and speech, and domain-
Shanghai200234,China
transfer effects suggest a possible connection between
:
C.Jiang Y.Yang(*) musical pitch and lexical tone processing (Gottfried &
InstituteofPsychology,ChineseAcademyofScience, Riester, 2000; Gottfried, Staby & Ziemer, 2001; Lee &
Jia4#,DatunRoad,
Hung, 2008; Wu & Lin, 2008). As such, examining
ChaoyangDistrict,Beijing100101,China
lexical tone processing in those who are known to have
e-mail:[email protected]
deficits in processing musical pitch should provide valuable
: :
J.P.Hamm(*) V.K.Lim I.J.Kirk evidence toward determining the extent to which music and
DepartmentofPsychology,UniversityofAuckland,
speechshareprocessingcomponents.
10SymondsStreet,
Congenital amusia (simply amusia, hereafter; Peretz,
Auckland1142,NewZealand
e-mail:[email protected] 2001) describes a lifelong deficit in the processing of
1110 MemCogn(2012)40:1109–1121
musical pitch variations in the absence of brain injury the controls, with 15 % of the amusic group scoring two or
(Ayotteetal.,2002;Peretzetal.,2002).Thesepitchdeficits more standard deviations below the mean of the controls.
manifest as a difficulty in making fine-grained pitch dis- Similarly, French-speaking amusics have been shown to be
criminations (Foxton, Dean, Gee, Peretz & Griffiths, 2004; impairedintheprocessingofMandarinandThailexicaltones
Hyde & Peretz, 2004; Jiang, Hamm, Lim, Kirk & Yang, (Tillmannetal.,2011).
2011), processing pitch-change direction (Foxton et al., Ofcourse,theFrench-speakingparticipantsinthesestud-
2004; Liu, Patel, Fourcin & Stewart, 2010), and deciding iesdidnotspeakMandarinChinese,andsothetoneswould
whether two sequences of pitches are the same or different not be processed as meaningful language. Lacking the se-
(Foxton et al., 2004; Hyde & Peretz, 2004; Jiang, Hamm, mantics, and presumably therefore lacking the input of the
Lim,Kirk&Yang,2010).Somestudieshavesuggestedthat language-processing system, it may not be surprising that
amusics may also have pitch memory deficits (Gosselin, they showed impairments on processing the pitch of these
Jolicœur & Peretz, 2009; Tillmann, Schulze & Foxton, stimuli. It has been speculated that amusics who speak a
2009), particularly with shorter tone spans (Williamson & tonal language might retain normal sensitivity to pitch
Stewart, 2010). However, whether or not the musical pitch changes that occur in their native language (Stewart,
deficits in amusia also manifest as pitch-processing deficits 2006). However, in our previous study (Jiang et al.,
inspeech iscurrentlydebated.Somehavearguedthat indi- 2010), we found that native speakers of Mandarin Chinese
vidualswithamusiadonothavecompromisedinterpretation with amusia were impaired in Mandarin speech intonation
and discrimination of Western speech intonation (Ayotte et processing during a question-versus-statement discrimina-
al.,2002;Peretzetal.,2002),whereasothershavesuggested tion. This result suggests that tonal language experience
that the pitch deficits in amusia extend to the processing of may not entirely compensate for deficits in intonation
emotionalprosody(Thompson,2007)andspeechintonation processing in amusia. Whether or not Mandarin-speaking
contours (including gliding-pitch analogues extracted from amusics also show impairments on the perception of
speechintonation;Hutchins,Zarate,Zatorre&Peretz,2010; Mandarin tones is of particular interest here.
Jiangetal.,2010;Liuetal.,2010;Patel,Foxton&Griffiths, Some evidence has suggested that this may be the case.
2005; Patel, Wong, Foxton, Lochy &Peretz, 2008). Nan, Sun and Peretz (2010) found that amusic Mandarin
It is well known that changes in tone influence word speakers performed worse than controls in a tone identifi-
meaning in tonal languages. In Mandarin Chinese, there cationtaskinvolvingmonosyllabicandbisyllabicwords.In
are four lexical tones, which vary in their contour shapes: addition, it has been shown that individuals with deficits in
high-level (Tone 1), mid-rising (Tone 2), falling-rising musical pitch processing also have impaired phonemic
(Tone 3), and high-falling (Tone 4) (see Fig. 1). For exam- awareness (Jones, Lucker, Zalewski, Brewer & Drayna,
ple,ma1means“mother,”ma2correspondsto“hemp,”ma3 2009a; Loui, Kroog, Zuk, Winner & Schlaug, 2011). This
to“horse,”andma4indicates“scold.”Totestwhetherornot suggeststhatthedeficitswithMandarintonesfoundbyNan
the discrimination of Mandarin pitch changes might be et al. may be related to reduced phonemic awareness in
problematic for Western amusic individuals, Nguyen, amusia.
Tillmann,GosselinandPeretz(2009)assessedamusicspeak- Categoricalperceptionofphonemesreflectsafundamen-
ers of French on their discrimination of pairs of Mandarin tal property of speech (e.g., Chang et al., 2010; Liberman,
lexical tones. The amusic participants performed worse than Cooper, Shankweiler & Studdert-Kennedy, 1967; Patel,
2008). Previous cross-language studies have indicated that
native Mandarin and Cantonese speakers show categorical
perceptionofMandarinlanguagetones,whereasadultswho
do not speak Mandarin do not show categorical perception
ofMandarintones(e.g.,Chan,Chuang&Wang,1975;Peng
et al., 2010; Wang, 1976; Xu, Gandour & Francis, 2006).
Categorical perception is not only found with speech
sounds,buthasalsobeenfoundintheprocessingofmusical
chordsandpitchintervals(Burns&Campbell,1994;Burns&
Ward,1978;Klein&Zatorre,2011;McMurray,Dennhardt&
Struck-Marcell, 2008; Siegel & Siegel, 1977; Zatorre &
Halpern,1979).Ithasbeensuggestedthat4-to6-month-old
infants discriminate the sound categories in both Mandarin
tones and music (Lynch & Eilers, 1992; Mattock, Molnar,
Polka & Burnham, 2008), but if they are not exposed to
Fig. 1 Pitch contours of Mandarin tones. Note: The numbers in
parenthesesindicatethepitchvaluesofthetonesonafive-levelscale Mandarinlanguage,oragivenmusicalcontext,theseabilities
MemCogn(2012)40:1109–1121 1111
arelostby9monthsforspeechtones(Mattocketal.,2008), decision can reflect training and practice (Livingston,
and by adulthood for music (Lynch & Eilers, 1992). Fur- Andrews&Harnad,1998).Whilethesharpnessoftheclassi-
thermore, listeners with music training outperformed those fication boundary indicates the consistency with which the
without music training in categorical perception studies stimuli near the position of the boundary are assigned into
involving Mandarin tones (Wu & Lin, 2008) or nonspeech their respective categories, it does not necessarily reflect
frequency continua (e.g., Howard, Rosen & Broad, 1992; whetherornotacategoricalchangeinperceptiontakesplace
Mirman, Holt & McClelland, 2004; Pisoni, 1977). These atthatboundary(Massaro,1987).
studies indicated that experience with tonal language and The second task is a discrimination task, in which pairs
music may affect the categorical perception of speech and of stimuli are presented for a same/different judgment. On
nonlinguistic frequency continua. different pairs, the two stimuli differ by a constant amount
It has been suggested that music and language share in terms of their physical dimension. If both stimuli of the
mechanismsthatcreateandmaintainlearnedsoundcatego- pair fall on the same side of the classification boundary,
ries(Patel,2008).Althoughthedevelopmentalprocessesfor they are coded as a within-category pair, but if they fall
sound categories may be domain-general, the end products on opposite sides of the classification boundary, they are
of development may be domain-specific (Patel, 2008). referred to as a between-category pair. The difference
Therefore, the ability to learn sound categories in one do- between the discrimination of between-category pairs and
main should have some predictive power with regard to within-category pairs is referred to as the peakedness of
sound category learning in the other domain (Patel, 2008, the discrimination.
p. 78). From this argument, it follows that deficits with Although thecriterion and definition for categorical per-
sound categories in one domain, such as the deficits with ception are still a matter of debate (e.g., Francis, Ciocca &
musicaltonesshownbyamusics,shouldbeassociatedwith Ng, 2003; Gerrits & Schouten, 2004; Liberman, Harris,
deficits with sound categories in another domain, such as Hoffman & Griffith, 1957; Massaro, 1998; Repp, Healy &
Mandarintonesifthedeficitsarepartofthedomain-general Crowder, 1979; Schouten, Gerrits & van Hessen, 2003),
developmentalprocesses.Conversely,ifthedeficitsinamu- thereisconsensusthat,whenstimuliareperceivedcategor-
sia are within the domain-specific representations, there ically, two tokens from two different categories are more
should be no association between the musical deficits in discerniblethanaretwotokensfromthesamecategorywith
amusiaand thecategorical perceptionof Mandarintones. an equivalent acoustic difference between them (Massaro,
To assess categorical perception, two tasks would be 1987).Namely,categoricalperceptioncanexplainwhyitis
required in order to produce unequivocal results (Massaro, easier to discriminate stimuli when the pairing is between
1987). It should be pointed out that we are considering the categories. This cross-boundary benefit is the defining fea-
weak formofcategorical perceptionthatMassaro(1987,p. tureofcategoricalperception(Massaro,1987).Ifthereisno
118)describes,whichiscapturedbytheimproved discrim- benefit for discriminations that cross the boundary relative
inationsthatoccurbetweenmembersofdifferentcategories, to within-boundary discriminations, there is no support for
relative to discriminations between members of the same asserting that categorical perception occurs.
category that differ by thesame physical amount. To deter- Becausethechangeinperformanceforstimulithatcross
mine such discriminations, the first task required is the a boundary is the defining characteristic of categorical per-
classification task, in which participants are required to ception, knowing the position of this boundary is highly
indicate to which of two categories they would assign a important.Therefore,althoughthesharpnessoftheclassifi-
given stimulus when it is presented in isolation. A set of cation boundary is not a critical measure to justify whether
stimuli are presented that change along a physical continu- or not categorical perception has occurred, the boundary’s
um for classification. Provided that the extreme exemplars positionduringtheclassificationtaskisanecessarymeasure
are distinguishable, it becomes possible to determine a in order to test for categorical perception in the subsequent
physicalstimuluslevelatwhichagivenparticipantisequal- discrimination task.
ly likely to classify the stimulus as either category. This The purpose of the present study was to investigate the
point of equality will be referred to as the classification categorical perception of lexical tones in Mandarin-speaking
boundary rather than as the categorical boundary, as the individualswithamusiabyemployingatraditionalcategorical-
latter term may be mistaken to imply that the classification perceptionparadigmthatincludedbothidentificationanddis-
task alone determines categorical perception. The slope of crimination tasks. The present study also investigated the
theboundarymaybesteeporshallow,anditisreferredtoas effects of pitch direction and stimulus context (speech vs.
thesharpness ofthe classification boundary. nonlinguisticanalogues)onthecategoricalperceptionoflexi-
Ofcourse,anyclassificationtaskwillproduceaclassifica- caltonesforMandarinamusics,becauseitisuncertainwhether
tionboundary,regardlessofwhetherornotthereisanaccom- ornotamusicshavegreaterdifficultywithdetectingrisingor
panying categorical change in perception. This change in fallingpitchchanges(Hyde&Peretz,2004;Jiangetal.,2011;
1112 MemCogn(2012)40:1109–1121
Peretzetal.,2002).AsisshowninFig.1,Tone1isahigh-level None of the participants had received extracurricular music
tone,whilethepitchcontoursofTone2andTone4arerising training,andnonereporteddifficultiesindiscriminatingMan-
andfallinglinearramps,respectively.Therefore,twotypesof darintones.Allhadnormalhearing,withmeanhearinglevels
continua (Tone 1–Tone 2 and Tone 1–Tone 4), using both of19.1and19.8dBHLfortherightandleftears,respectively,
natural speech and nonlinguistic analogues, were employed asmeasuredbypure-toneaudiometryat125,250,500,1000,
in the present study. We hypothesized that if amusia is a and2000Hz.EthicalapprovalwasobtainedfromtheInstitute
domain-general pitch-processing deficit, thenamusic individ- ofPsychology,ChineseAcademyofSciences,andinformed
ualswouldbelikelytohavegreaterdifficultyindetectingthe consentwasobtainedfromalloftheparticipants.
changes in pitch for language stimuli as well, indicating a
shared sound-category learning mechanism for language and Stimuli
music.Alternatively,ifthepitchdeficitsinamusiaaredomain-
specific, then amusic individuals should not be impaired, ThespeechstimuliweretheMandarinvowel/i/withahigh-
whichwouldsuggestthatmusicandlanguagedonotsharea level tone (Tone 1) spoken by a male native speaker of
commonlearningmechanismforsoundcategories. Mandarin Chinese. On the basis of the Tone 1 natural-
speech template, two tonal continua were synthesized by
means of Praat software (Boersma, 2001). These two tonal
Method continuaranged fromahigh-leveltonetoamid-risingtone
(yi1means“clothing,”andyi2indicates“aunt”;i.e.,Tone1–
Participants Tone2)andfromahigh-leveltonetoahigh-fallingtone(yi1
means “clothing,” and yi4 indicates “difference”; i.e., Tone
The two groups of participants contained 15 amusic adults 1–Tone4),respectively.Eachcontinuumcontained11stim-
and 15 control adults. Of these participants, 11 amusic and uli, with a step size of 3 Hz, which is a rather large differ-
10 control adults had participated in our previous studies ence in psychological terms (Wang, 1976). In these two
(Jiang et al., 2010, 2011). All of the participants were tonal continua, the peak frequency of all stimuli was fixed
recruited by means of advertisements in the bulletin board at228Hz,andeachstimuluslasted350ms(seeFig.2).The
systems of universities in Beijing. The Montreal Battery of ends of the two tonal continua, Steps 1 and 11, were all
Evaluation of Amusia (MBEA) was to be used to diagnose judged to be good examples of Mandarin Tone 1, Tone 2,
thepresenceorabsenceofamusiaintheseparticipants(Nan andTone4bysixnativeChinese(Mandarin)speakerswho
et al., 2010; Peretz, Champod & Hyde, 2003). The charac- didnottake part inthe experiments.
teristicsofeachparticipantgroupareshowninTable1.All In addition to the speech stimuli, an equal number of
but two amusics and one control participant were right- nonlinguistic analogues were created. These nonlinguistic
handed,asassessedbytheEdinburghHandednessInventory analogues were created using Praat software to extract the
(Oldfield,1971).Moreover,adetailedquestionnairewaspre- fundamentalfrequenciesofthespeechmaterials.Essentially,
sented to gather further information about the participants. thelinguisticinformationwasremoved,whilethetimingsof
the speech materials remained unchanged. Moreover, the
newlycreatedsoundwasmodifiedtoensurethatitsacoustic
Table 1 Participants’ characteristics and individual scores on the
waveformamplitudedifferedfromtheoriginalspeechsound
MontrealBatteryofEvaluationofAmusia(MBEA)
bynomorethan±3dBineachpair.
Demographic Amusic(n015) Control(n015) tTest For the practice task, 11 stimuli were presented, with
Characteristics linearrampsrangingfromTone1toTone2andfromTone
1 to Tone 4 for the speech and nonlinguistic analogues,
Meanage 24(3.3) 23(1.8) n.s.
respectively. The difference between the practice stimuli
Gender 7M,8F 8M,7F
and the experimental stimuli was that the former were
Yearseducation 17(2.3) 16(1.3) n.s.
derived from the Mandarin vowel /a/, and the latter from
GlobalscoreofMBEA 19(2.3) 27(1.6) p<.001
theMandarin vowel /i/.
Scalesubtest 18(3.4) 27(2.0) p<.001
Contoursubtest 19(2.7) 26(2.3) p<.001
Procedure
Intervalsubtest 18(2.7) 27(1.6) p<.001
Rhythmsubtest 21(4.4) 26(2.4) p<.001
Allparticipantsengagedinthetwotonal-continuaidentifica-
Metersubtest 21(3.9) 25(2.7) p0.001
tionanddiscriminationtasksforbothspeechandthenonlin-
Memorysubtest 20(4.1) 28(2.3) p<.001
guisticanalogue,respectively.Thefourtaskswerepresented
inseparateblocksinacounterbalancedorder.Ineachcontin-
Parenthesesinthedatarowsindicatestandarddeviations.F,female;M,
male uum identification task, each stimulus was repeated four
MemCogn(2012)40:1109–1121 1113
Fig.2 Pitchpatternsofthe
tonalcontinua.(a)Tone1–Tone
2continuum.(b)Tone1–Tone
4continuum
times, resulting in 44 randomly ordered trials for speech. Results and discussion
Furthermore,44randomlyorderedtrialswerealsopresented
for nonlinguistic analogues in the two continua. The partic- Classification task
ipants were required to press the “1” key if the stimulus
resembled a “high-level tone (Tone 1),” and the “2” key to IdentificationcurvesforthetwogroupsareplottedinFig.3.
indicate a “mid-rising tone (Tone 2)” in the Tone 1–Tone 2 Ascanbeseen,theamusicparticipantsshowasharpnessof
continuum for both speech and the nonlinguistic analogue. theclassificationboundarysimilartothatofthecontrols.A
Similarly,the“2”keywascodedasa“high-fallingtone(Tone logisticregressionanalysiswasperformedusinggeneralized
4)”intheTone1–Tone4continuumforbothspeechandthe linear models using the R statistical software package (R
nonlinguisticanalogue. Development Core Team, 2009). We calculated the slope
In each tonal continuum discrimination task, nine (b ) and intercept (b ) regression coefficients for each par-
1 0
pairs were derived by combining two stimuli separated ticipant,withtheslopebeingusedtoindicatethesharpness
by two steps, such as 1–3, 2–4, 3–5, and so on. The of the classification boundary. The regression equation was
different pairs included nine pairs for each tonal con- used to predict the discrimination value (X) for each stimu-
tinuum in the forward (1–3, 2–4, 3–5, 4–6, 5–7, 6–8, lus step (1–11). Because logistic regression works in logit
7–9, 8–10, 9–11) and reverse (3–1, 4–2, 5–3, etc.) space,thesepredictedvaluesmustbetransformedbackinto
orders, respectively. Identical pairs were constructed by thedataspaceviathefollowingequation:data0ex/(ex+1).
pairing each stimulus in a tonal continuum with itself. The sum of the squared deviations between these predicted
The order of the stimuli in each pair was counterbalanced datavaluesandtheobservedvalueswerethenexpressedas
with a 200-ms interstimulus interval (ISI), and each pair thepercentagereductioninvariationrelativetothesquared
was presented four times. As a result, a total 116 pairs, deviationabouttheobservedmean.Thisreductionwasused
including 72 different pairs and 44 identical pairs, were asameasureofthegoodnessoffitforeachparticipant.The
presented randomly for speech and for the nonlinguistic range over all participants and conditions was between
analogue, respectively, in each tonal continuum. For the 42.4 % and 99.8 %, with a mean percentage reduction of
fourdiscriminationtasks,theparticipantswererequiredto 89.7 %. It was concluded that the logistic regression pro-
judgewhetherthetwostimuliwerethesameordifferentby videdagoodfittotheobserveddataattheindividuallevel,
pressingthe“1”keyiftheyheardthesamestimulusorthe and so an analysis of the b and b parameters was
1 0
“2”keytoindicatedifferentstimuli.Fortheanalyses,ahit conducted.
wasdefinedwhenadifferentpairwasindicatedas“differ- In order to determine whether there were any effects on
ent,”whileafalsealarmwasdefinedwhenanidenticalpair thesharpnessoftheclassificationboundary,theslopeswere
wasindicatedas“different.” analyzed in a three-way mixed-factor analysis of variance
In the practice task, the 11 stimuli were presented only (ANOVA), with Group as a between-subjects factor and
once in a random order for the identification task. For the Stimulus Context (speech vs. nonspeech analogue) and
discrimination task, eight practice pairs comprising two Continuum (Tone 1–Tone 2 vs. Tone 1–Tone 4) as within-
different stimuli separated by three steps were presented subjects factors. None of the main effects or interactions
randomly. All of the stimuli were presented binaurally reached significance (all ps > .2).
through Philips SHM1900 headphones in a soundproofed Although caution is required when interpreting a null
room. result, this is consistent with previous studies, suggesting
1114 MemCogn(2012)40:1109–1121
Fig. 3 Identification curves for the two groups in each task. (a) Tone 1–Tone 2 continuum for speech. (b) Tone 1–Tone 2 continuum for a
nonlinguisticanalogue.(c)Tone1–Tone4continuumforspeech.(d)Tone1–Tone4continuumforanonlinguisticanalogue
that the identification task reflects the listeners’ native lan- between thebeginning andendofthelevel toneis0,while
guage experiences (Chan et al., 1975; Peng et al., 2010; the difference between the beginning and end of the rising
Wang, 1976; Xu et al., 2006) and that phonetic memory is and falling tones equates to 2.44 semitones at Step 11.
employed to do the identification task (Pisoni, 1973). The Amusics are capable of discriminating musical tones that
phonetic-memory code is thought to be stable, due to con- differ by this amount, although their performance is below
tactwithrepresentationsresidinginlong-termmemory(Xu that of controls (Jiang et al., 2011). Each step in the tonal
et al., 2006, p. 1069). The present lack of a difference continua equates to approximately 0.24 semitones (range 0
betweenamusicsandthecontrolswithrespecttothesharp- 0.23to0.26,duetotheexponentialrelationshipbetweenthe
ness of the classification boundaries is consistent with the physicalfrequencyandperceivedsemitones),whichinturn
suggestion that amusics have normal long-term phonetic is below their discrimination threshold for individual tones
memory (Jones, Zalewski, Brewer, Lucker & Drayna, (Jiang et al., 2011). If the amusics compare each presented
2009b).Anormallong-termphoneticrepresentationinamu- stimuluswithanormallong-termphoneticrepresentation,it
sia would be consistent with the suggestion that music and mightbeexpectedthatthestimuliwouldnotbeperceivedas
language havespecializedrepresentations (Patel, 2008). different from this representation until the tone and repre-
Although the similar sharpnesses of the boundaries sentation differ by somewhere between one-half and one
would be consistent with preserved categorical perception semitone (Jiang et al., 2010). As a stimulus moves farther
of the lexical tones in amusia, this finding does not lead from one end of the continuum, the difference between the
unequivocallytosuchaconclusion.Analternativeexplana- stimulus and the long-term phonetic representation would
tionwouldbeasfollows.Thedifferenceintonalfrequency increase and move into the detectable range. At the same
MemCogn(2012)40:1109–1121 1115
time, the stimulus becomes more similar to the alternative p < .001]. All other interactions were not significant (p >
long-termphoneticrepresentationandmovesquicklyintoa .05). Post hoc Bonferroni-corrected t tests revealed a sig-
range that is nondetectable. With these performance pres- nificantdifferencebetweenthegroupsintheboundaryposi-
suresworkingatbothendsofthecontinua,theresultcould tion for the speech stimuli (p < .001), but not for the
be that the sharpness of the classification boundary reflects nonlinguisticanalogues(p>.05).
thesecompetingforces“squeezing”theboundaryintoplace, Cross-linguisticstudies(Chanetal.,1975;Francisetal.,
rather than indicating a sudden change in the categorical 2003; Peng et al., 2010; Wang, 1976; Xu et al., 2006)
perception of the stimuli. This squeezing due to poor dis- comparing Mandarin- and English-/German-speaking par-
crimination of lexical tones would also account for the ticipants on their classification of Mandarin tones have
tendency of the boundary position to be more central for found no significant difference with respect to the position
theamusics than for the controls. of the classification boundary, although the boundary is
Unlike the sharpness measure, the position of the classi- shallowerforthenonspeakers.Therefore,thepresentpattern
fication boundary is a critical measure in order to test for for the amusics is unlike that of nonspeakers of Mandarin
categoricalperceptioninthesubsequentdiscriminationtask. and may be due to an insensitivity to pitch contour for the
OnthebasisoftheformulapresentedinXuetal.(2006),the amusics.
position of the classification boundary (x ) was calculated As can be seen from Table 2, the boundaries of the
cb
foreachparticipantfromthelogisticregressioncoefficients amusic group are shifted toward the mid-rising and high-
(b andb ) as follows: fallingtoneendsofthetwocontinua.Thisshiftsuggeststhat
0 1
the amusic participants are less able todetect thechange in
(cid:1) (cid:3)
0:5 b pitchoftherisingandfallingtones(Tones2and4),andso
b þb x ¼log ¼0)x ¼(cid:2) 0 ð1Þ
0 1 cb e 1(cid:2)0:5 cb b classified them as level, or not changing (Tone 1). This is
1
consistent with the notion that Mandarin-speaking amusics
As can be seen in Fig. 2, the higher the value of x , the have impaired tone processing with speech material. An
cb
closertheboundaryistoTone2orTone4.Ascanbeseenin insensitivity to small pitch changes for the amusics is con-
Table 2, the amusic group’s x score is higher than the sistent with the finding of problems in detecting the direc-
cb
controls’, suggesting that the positions of the classification tionofasmallpitchchange(Foxtonetal.,2004)withfine-
boundaries for the amusic group may be shifted toward the grained pitch discriminations (Jiang et al., 2011), and it is
mid-rising (Tone 2) and high-falling (Tone 4) ends of the also consistent with the finding that Mandarin amusic
two tonal continua. This was confirmed by a mixed-factor speakers have problems in processing melodic contour and
three-way ANOVA, which was conducted to determine the speech intonation(Jiang etal., 2010).
impactsofparticipantgroup(amusicsvs.controls),stimulus
context(speechvs.nonlinguistic analogue), andcontinuum Discriminationtask
type (Tone 1–Tone 2 vs. Tone 1–Tone 4) on the boundary
position,withtheparticipantgroup asthebetween-subjects On the discrimination task, the amusics were at chance
variable, and stimulus context and continuum type as the levels for all pairs. The obtained discrimination curves for
within-subjects variables. The analysis revealed significant the amusic group are lower than those of the controls for
main effects of group [F(1, 28) 0 7.14, p < .001], stimulus both speech and the nonlinguistic analogue, as shown in
context [F(1, 28) 0 15.60, p < .001], and continuum type Fig. 4.
[F(1, 28) 0 20.54, p < .001], as well as an interaction Onthebasisofthepositionoftheclassificationboundary
of stimuluscontextandcontinuumtype[F(1,28)022.04, (x ),wecalculateddiscriminationscores(thepercentageof
cb
Table2 Theregressioncoefficients(b andb )andthederivedclassificationboundaryposition(x )foreachgroup
0 1 cb
AmusicGroup ControlGroup
b b x 0−b /b b b x 0−b /b
0 1 cb 0 1 0 1 cb 0 1
T1–T2S −6.8(3.4) 1.0(0.6) 7.3(1.6) −8.9(4.3) 1.4(0.8) 6.4(1.2)
T1–T4S −7.6(3.5) 1.4(0.7) 5.6(0.9) −9.2(2.9) 1.9(0.5) 4.9(0.6)
T1–T2NL −7.0(2.8) 1.3(0.5) 5.4(1.0) −8.4(4.0) 1.7(0.9) 5.2(1.2)
T1–T4NL −8.3(3.8) 1.6(0.8) 5.3(0.8) −7.9(3.4) 1.6(0.7) 4.9(0.8)
S, speech stimuli, NL, nonlinguistic analogue stimuli; T1–T2, Tone 1–Tone 2 continuum; T1–T4, Tone 1–Tone 4 continuum. The unit of the
derivedclassificationboundarypositionx isstepnumber
cb
1116 MemCogn(2012)40:1109–1121
Fig.4 Discriminationcurves
forthetwogroups.(a)Tone
1–Tone2continuumfor
speech.(b)Tone1–Tone2
continuumforanonlinguistic
analogue.(c)Tone1–Tone4
continuumforspeech.(d)Tone
1–Tone4continuumfora
nonlinguisticanalogue
hits minus false alarms) for between-category and within- mixed-factor ANOVA that included Group as a between-
categorypairsforeachparticipant.Thesewerecalculatedas subjects factor confirmed the Group × Category Type
follows. If the classification task indicated that a partici- interactionimpliedbytheseparateanalysesabove[F(1,28)0
pant’s classification boundary was at position 4.5, then the 5.04,p<.05].PosthocBonferroni-correctedttestsrevealed
scores for Stimulus Pairs 3–5 and 4–6 would be averaged thattheamusicparticipantsperformedworsethanthecontrols
and coded as between-category comparisons, while the inbothwithin-categoryandbetween-categorydiscriminations
remaining comparisons would be coded as within-category (allps<.05).
comparisons. AscanbeseeninFig.5,theperformancesof Figure5showsthemeanpercentagesofhitsminusfalse
both groups were similar on the two continua. Although alarms for both groups on within- and between-category
both groups performed better with speech than with the discriminations of Tone 1–Tone 2 and Tone 1–Tone 4 con-
nonlinguisticanalogue,theamusicparticipantsdidnotben- tinuaofspeechandnonlinguisticanalogues.Alsoshownin
efit from discriminations that crossed the classification Fig.5aretheindividualparticipants’scores,whichshowan
boundary for either stimulus type. In contrast, the control overlap in performance between the groups. Although one
participants’ discriminations did benefit for both stimulus or more individual amusic participants did score two or
types when the discriminations crossed the classification more standard deviations below the mean of the controls
boundary. in each of the conditions except for the Tone 1–Tone 2
Thiswasconfirmedbyathree-wayANOVAperformedon between-category discriminations of the nonlinguistic ana-
thepercentageofhitsminusthepercentageoffalsealarmsfor logues,noindividualamusicparticipantscoredtwoormore
the between- and within-category discrimination for each standarddeviationsbelowthemeanofthecontrolsinallof
group,wherestimuluscontext(speechvs.nonlinguisticana- the other conditions. However, correlations between an
logue),categorytype(between-categoryvs.within-category), individual’s melodic score from the MBEA, which is the
andcontinuumtype(Tone1–Tone2vs.Tone1–Tone4)were average score on the first three subtests, and their discrim-
the within-subjects variables. For the amusic group, we ination performance revealed significant correlations for
found a main effect of stimulus context [F(1, 14) 0 5.69, boththeTone1–Tone2andTone1–Tone4speechcontinua
p < .05], with all other main effects and interactions being for between-category discriminations [r(28) 0 .49, p < .05;
nonsignificant. The controls, however, showed main effects r(28) 0 .51, p < .05]. The correlation was also significant
of category type [F(1, 14) 0 28.92, p < .001] and stimulus fortheTone1–Tone4speechcontinuumonwithin-category
context [F(1, 14) 0 14.39, p < .01], with all other main discriminations[r(28)0.38,p<.05].Thesecorrelationsagain
effects and interactions being nonsignificant. A four-way indicatethatperformancewithmusicalstimuliontheMBEA
MemCogn(2012)40:1109–1121 1117
Fig.5 Percentagesofhits
minusfalsealarmsforthetwo
groupsindiscriminatingthe
fourstimuluscontextsduring
comparisonsthatremained
withinapotentialcategoryor
thatcrossedtheboundary,as
determinedbytheidentification
taskforeachindividual
participant.(a)Tone1–Tone2
continuumforspeech.(b)Tone
1–Tone2continuumfora
nonlinguisticanalogue.(c)
Tone1–Tone4continuumfor
speech.(d)Tone1–Tone4
continuumforanonlinguistic
analogue
predictsperformanceonlinguistictonediscriminations,even Threeamusicparticipantsscoredtwoormorestandarddevia-
for those who speak the language. No other correlation tions below the mean of the controls only for the speech
reachedsignificance. stimuli of the Tone 1–Tone 4 continuum. Correlations with
As noted above, the peakedness measure represents the the melodic scoreandpeakednessmeasuresweresignificant
magnitude of the benefit for discriminations that cross the forthespeechstimuliinboththeTone1–Tone2[r(28)0.40,
classification boundary. The peakedness of the discrimina- p < .05] and the Tone 1–Tone 4 [r(28) 0 .44, p < .05]
tion performance for each participant was calculated and continua. This again suggests a relationship between music
compared between groups. As can be seen in Fig. 6, the
amusic group shows reduced peakedness scores relative to
the controls, indicating that they experienced less of a ben-
efitforcrossingtheclassificationboundarythanthecontrols
did.ThisisthesameeffectthatwasindicatedbytheGroup
× Category Type interaction from the analysis of the dis-
criminationscoresabove.Thepeakednessvalueswereana-
lyzed with a mixed-factor three-way ANOVA with Group
(amusics vs. controls) as a between-subjects factor and
Stimulus Context (speech vs. nonlinguistic analogue) and
Continuum Type (Tone 1–Tone 2 vs. Tone 1–Tone 4) as
within-subjects factors. The results revealed a significant
main effect of group [F(1, 14) 0 5.43, p < .05]. No other
main effect orinteraction reached significance. Fig.6 Peakednessscoresforthetwogroupsintheeachtonalcontin-
uum.T1–T2S,Tone1–Tone2continuumforspeech;T1–T2NL,Tone
Figure 6 shows the mean and individual scores for the
1–Tone2continuumforanonlinguisticanalogue;T1–T4S,Tone1–
peakednessmeasurefortheTone1–Tone2andTone1–Tone Tone4continuumforspeech;T1–T4NL,Tone1–Tone4continuum
4 continua for both speech and the nonlinguistic analogues. foranonlinguisticanalogue
1118 MemCogn(2012)40:1109–1121
processing and categorical perception of the Mandarin thefactthatamusicshaveshowndeficitsinperformingfine-
tones, at least in the context of speech. No other correlation grained pitch discriminations and pitch contour discrimina-
reached significance. tions in previous studies (Ayotte et al., 2002; Foxton et al.,
Elevenofthe15amusicparticipantsinthepresentstudy 2004;Hyde&Peretz,2004;Jiangetal.,2010,2011;Peretz
had participated in a two-tone discrimination task in our etal., 2002).
previous study (Jiang et al., 2011). Correlations between Although the participants showed better discrimination
their two-tone discrimination performance and the present for both within- and between-category pairs for speech
three discrimination measures (within-category, between- stimuli as compared to nonlinguistic analogues, this did
category, and the peakedness of discriminations) were also notleadtoamaineffectofstimuluscontextforthepeaked-
calculatedforeachtask.FortheTone1–Tone2continuum, ness measure. This is because peakedness quantifies the
wefoundsignificantcorrelationsbetweenthetwo-tonedis- difference between between-category and within-category
crimination performance and the within-category and discriminations, irrespective of the level of performance
between-category discrimination of speech stimuli [rs(9) 0 for each condition individually. The amusic participants
.61and.63,respectively;allps<.05].Thecorrelationswere did not differ in their discrimination performance between
similar between their two-tone discrimination performance thetwotonalcontinua,whichisinlinewithpreviousstudies
and the within-category and between-category discrimina- that have suggested that individuals with amusia show no
tionsforthecorrespondingnonlinguisticanalogues,aswell difference in impairment in detecting rising or falling pitch
[rs(9)0.69and.71,respectively;allps<.05].FortheTone changes inpitch(Hyde &Peretz, 2004;Jiang etal.,2011).
1–Tone 4 continuum, their two-tone discrimination perfor- Despitethefindingthattheamusicparticipants’discrim-
mancewassignificantlycorrelatedwiththewithin-category ination performance did not benefit when a stimulus pair
and between-category discriminations of the nonlinguistic crossed the classification boundary for either speech or the
analogues [rs(9) 0 .65 and .62, respectively; all ps < .05]. nonlinguistic analogues, amusic participants did discrimi-
No other significant correlations were found (all ps > .05). nate speech stimuli better than the nonlinguistic analogue
These correlations are consistent with the idea that musical stimuli.Thiswasapatternsimilartothatofthecontrols,and
pitchprocessingandlanguagetoneprocessingshareacom- it is consistent with the results reported by Peng et al.
mon underlying deficit in those with amusia. (2010), but inconsistent with the data of Xu et al. (2006).
Thisdiscrepancyintheliteraturemaybeattributedtodiffer-
ences between the nonspeech stimuli used in the various
Generaldiscussion studies. For example, the nonlinguistic analogue stimuli in
the present study were pure tones rather than the harmonic
Overall, the participants with amusia showed no improve- tones employed by Xu et al. Speech and harmonic tones
ment for discrimination pairs that crossed the classification contain richer harmonic structures, and the “richness of har-
boundary, and their peakedness-of-discrimination scores monics”facilitatespitchperception,ascomparedtopuretones
were lower than those of the controls. The present data are (e.g., Bernstein & Oxenham, 2003; Lütkenhöner, Seither &
consistentwiththosefrompreviousstudies(Liuetal.,2012; Seither-Preisler, 2006; Peng et al., 2010; Tervaniemi et al.,
Nanetal.,2010)suggestingthatMandarinamusicshavean 2000). It is also possible that linguistic information may
impairment with processing Mandarin lexical tones, and facilitate pitch perception for speech stimuli relative to non-
they extend these findings to suggest that individuals with linguisticanalogues.
amusialack categorical perception ofMandarin tones. Interestingly, the pattern of discrimination shown by the
According to a multistore model (Xu et al., 2006), sen- Mandarin amusic participants with the Mandarin speech
sory,short-term,andlong-termformsofcategoricalmemo- stimuli was similar to that shown by English participants
ry are involved in categorical perception. As noted above, (Xuetal.,2006),whoalsofailedtoshowacross-boundary
thesimilarityinthesharpnessoftheclassificationboundary benefit in their discrimination of Mandarin tones. It is as-
between the amusics and the controls is consistent with the sumed that the English participants could perform the tone
suggestion that amusics may have normal long-term cate- discrimination up until the age of 6 months, and that they
gorical phonetic memory. Therefore, the degraded discrim- then lost this ability due to lack of early exposure to the
inationfortheamusicgroupcouldbeattributedtodeficitsin tones (Mattock et al., 2008). It may be that congenital
sensory and/or short-term memory. This is consistent with amusia effectively negates the preserving effect that expo-
recent studies that have suggested a short-term pitch mem- sureprovides.However,itremainsunknownwhetherornot
orydeficitinamusia(Gosselin etal., 2009;Tillmannetal., amusic individuals could initially discriminate the tones up
2009;Williamson&Stewart,2010).Sensorymemoryrefers to the age of 6 months and later lost this ability, similar to
to the unanalyzed raw and fine-grain-analyzed sensory theEnglishparticipants(Mattocketal.,2008).Alternatively,
codes (Xu et al., 2006), and deficits here could account for congenital amusia may interfere with tonal processing at all