THE MOZART EFFECT: AN INVESTIGATION INTO CONTRIBUTIONS OF THE LEFT AND RIGHT HEMISPHERE EMILY BAUMAN AND JEHAN COUTU Abstract This study was conductd to xamin th natur of th Mozart ffct, and to dtrmin th intr and intrahmisphr ffcts that latralizing diffrnt typs of musical stimuli may hav on spatial-tmporal rasoning. Participants wr 49 collg studnts from a small, libral arts univrsity in cntral Nw York. Participants wr randomly assignd to a Mozart, jazz, or a control condition and askd to complt a numbr of papr-and-pncil and computrizd tasks involving spatial transformations whil music was playd to altrnat ars. Rsult show th prdictd intraction btwn music condition and ars was obsrvd only for th raction tims of lft handrs, and occurrd in both th Mozart and jazz conditions. Implications for th natur of brain asymmtry among lft handd individuals and for furthr rsarch ar discussd. Introduction Rsarch in th past dcad has providd conflicting vidnc rgarding th nhancing ffct of Mozart s music on cognitiv task prformanc. Rauschr, Shaw, and Ky (1993) originally found a substantial incras in spatial-tmporal IQ scors on a subtst of th Stanford-Bint Intllignc Scal following xposur to Mozart s music compard to ithr silnc or rlaxation music. Subsqunt rsarch both supports and fails to support th occurrnc of this so-calld Mozart ffct. In accordanc with th original study, Rauschr, Shaw, and Ky (1995), Ridout, Doughrty, and Wrnrt (1998), and Ridout and Taylor (1997) prsntd subjcts with a papr folding and cutting task, a masur of abstract/spatial rasoning with intrnal manipulation of spatial-tmporal pattrns, and found a significant incras in task prformanc aftr listning to Mozart. Othr studis hav usd th Ravn Advancd Progrssiv Matrics, a gnral tst of intllignc that rquirs spatial aptitud, inductiv rasoning, and prcptual accuracy as assssd by matrix/symbol compltion tasks, and faild to obsrv any improvmnt in prformanc following xposur to Mozart s music (Nwman, Rosnbach, Burns, Latimr, Matocha, & Vogt, 1995; Stough, Krkin, Bats, & Mangan, 1994). Stl, Ball, and Runk (1997) usd a backwards digit span task, a corrlat of Ravn s Progrssiv Matrics involving rotation or transformation of squnc as a masur of tmporal rasoning, and also faild to find vidnc of a Mozart ffct. Such contradictions indicat that th ffct may not b robust or may b limitd to a subclass of spatial abilitis. In an attmpt to rconcil th disparat vidnc rgarding th Mozart ffct, Rauschr and Shaw (1998) spcify that th ssntial componnts rquird to produc th ffct includ tasks involving spatial imagry and mntal transformation of form. Such tasks would includ papr folding and maz tasks, and would xclud digit span, pattrn analysis, and Ravn s tsts bcaus thy masur analytic intllignc rathr than spatial-tmporal ability. Rauschr and Shaw propos that th nhancing ffct of Mozart s music on this typ of cognitiv task is du to an organizing ffct on cortical nurons involvd in spatialtmporal procssing. It is possibl, howvr, that th bnficial ffct of music, if rplicatd, occurs for othr rasons, such as a gnral incras in arousal or rduction of comptition btwn th crbral hmisphrs for spatial procssing. Farah (1986) claims that thr is a lft hmisphr locus for th ability to gnrat a spatial mntal imag, whil Corballis (1997) and Ditunno and Mann (1990) argu for rlativ right hmisphr spcialization in visual-spatial transformations. Rsarch on th diffrntial procssing capacitis of th crbral hmisphrs for mlodic stimuli suggsts right hmisphr supriority for th holistic procssing that is charactristic of nonmusicians (Bvr & Chiarllo, 1974). In addition, it has bn shown that th amplituds of vnt-rlatd potntials ar gratr for th right compard to th lft hmisphr whil listning to a mlody (Thomas & Shucard, 1983). Such vidnc implis a right hmisphr bias in procssing musical stimuli in musically naïv listnrs. Colgat Univrsity Journal of th Scincs 141
It has also bn notd that bimodal hmisphric stimulation of th right hmisphr with music and tactual stimuli prsntd to th lft ar and lft hand, rspctivly, rsults in an intrfrnc ffct, which rducs th fficacy of th right hmisphr in procssing th lattr (Smith, Chu, & Edmonston, 1977). A dcrmnt in prformanc on th haptic task was not obsrvd during bimodal stimulation of th lft hmisphr, rlativ to th control condition of no music, probably bcaus of a floor ffct. On th othr hand, whr music was playd to th lft ar during right hand discrimination of complx Braill forms, an improvmnt in prformanc occurrd rlativ to th control condition or whn music was prsntd to th right ar. It was hypothsizd that th bnficial ffct of music playd to th contralatral ar on right hand prformanc involvd rduction of intrhmis phric comptition for control of tactual procssing, by providing th right hmisphr with its own task (music). Extnding this lin of rasoning, thr may or may not b an ffct of music on prformanc of a spatial task, dpnding on whthr thr is comptition within hmisphrs for allocation of its attntional rsourcs and whthr thr is hmisphric rivalry for control of task prformanc. Th prsnt study invstigatd ths altrnativ xplanations for th Mozart ffct whil attmpting to rplicat it. W sought to tst th conflicting hypothss prsntd by Farah (1986), that th lft hmisphr is rquird for mntal imag gnration, and by Corballis (1997) and Ditunno and Mann (1990), that thr is a right hmisphr advantag for mntal rotation, in ordr to dtrmin th rlativ contributions of both hmisphrs to spatial procssing, and whthr ths contributions ar affctd by musical stimuli during spatial task prformanc. It is possibl, howvr, that th mod of problm solving prviously tstd diffrs in trms of th cognitiv stratgis dmandd by th tasks, causing thm to b latralizd diffrntly. Mntal imag gnration rquirs th ability to rconstruct th apparancs of objcts and scns not currntly in viw from long-trm mmory rprsntations of thm (Farah, 1986), whil mntal rotation is a visual-spatial transformation that rquirs th ability to construct a mntal imag of a prsntd stimulus, mntally turn, twist, or rotat this imag, and match th manipulatd imag to a prsntd standard (Ditunno & Mann, 1990). Ths altrnat spatial tasks may bnfit from distinctly diffrnt stratgis that may b mdiatd by diffrnt hmisphrs, thrfor accounting for th variations in rsults rgarding th functional asymmtry of th crbral hmisphrs. To tst th hypothss, participants compltd a baslin masur of thir ability to prform on spatial tasks involving mntal transformation. Subsquntly, thy listnd to classical music, jazz, or whit nois during as wll as immdiatly bfor prformanc of similar spatial tasks. Music was latralizd to th lft ar/right hmisphr or right ar/lft hmisphr in ordr to xamin whthr music has a facilitating or inhibiting ffct on spatial prformanc, dpnding on th hmisphr to which it is dirctd. Sinc th spatial transformation task in th prsnt xprimnt coincids with thos utilizd by Corballis (1997) and Ditunno and Mann (1990), w xpctd to find a similar right hmisphr bias for spatial procssing. Spcifically, w prdictd that prformanc on spatial tasks would b impaird whn music was dirctd to th lft ar/right hmisphr, du to comptition for th sam hmisphr s attntional mchanisms, whil thr would b no dcrmnt in prformanc in th right ar/lft hmisphr conditions. W xpctd that th lattr condition would provid ach hmisphr with its own stimulus to procss, consquntly liminating any intrahmisphric comptition that could ngativly affct task prformanc. Adopting anothr prspctiv, Rauschr and Shaw (1995) hypothsiz that Mozart xploits th inhrnt rprtoir of spatial-tmporal firing pattrns in th cortx, lading to an organizational ffct on ths firing pattrns so that thy ar xcitd and primd for th xcution of highr brain functions, lik th right hmisphr procsss of spatial-tmporal rasoning. This hypothsis rsults in th contrary prdiction that whn music is dirctd to th lft ar/right hmisphr thr will b a gratr nhancmnt in prformanc during xposur to Mozart than during xposur to jazz or whit nois. Mthod Participants Forty-nin (13 mals and 36 fmals) undrgraduat studnt voluntrs at a highly-slctiv libral-arts institution in upstat Nw York. 142 Colgat Univrsity Journal of th Scincs
Matrials Apparatus. Two rooms wr usd for this xprimnt, both containing th sam apparatus. Each room had in it two tabls and two chairs. On th first tabl was a pncil as wll as a brif dscription of our xprimnt, a consnt form, a handdnss survy, and a twnty qustion tst takn from th Diffrntial Aptitud Tst. On th othr tabl was a computr with a kyboard. Th computr was usd to prsnt two sts of problms adaptd from th Diffrntial Aptitud Tst and to rcord accuracy and latncy of participants rsponss. Also on th tabl was a tap rcordr with a st of hadphons attachd, and connctd to th hadphons was a switch controlling which ar th music from th tap rcordr was playd into. In ach tap rcordr was a tap containing on sid of Mozart s music rcordd from Mozart For Your Mind, and on sid of th Mils Davis Quintt rcordd from Round About Midnight. Procdur. Subjcts wr brought into th room and satd at a tabl whr thy rad a brif synopsis of our xprimnt, and wr askd to sign a consnt form. Subjcts wr thn givn a short qustionnair to dtrmin handdnss, following which thy wr administrd a papr and pncil tst consisting of 20 itms from th Diffrntial Aptitud Tst. In this tst th subjct was shown a pattrn on th lft and four comparison stimuli on th right. Subjcts had to dtrmin which of th four objcts on th right was cratd from th pattrn on th lft. Upon compltion of th writtn portion, subjcts wr placd into on of thr groups (classical music, jazz music, or whit nois) basd on th numbr of rrors mad on th papr and pncil tst. An ffort was mad to construct groups so that thy had th sam avrag prformanc on th Diffrntial Aptitud Tst. Aftr subjcts wr placd into a music or nois group, thy wr satd at a computr and askd to plac a st of hadphons ovr thir ars. Dpnding upon which group th subjcts wr placd in, thy hard that spcific typ of music or whit nois through th hadphons. Each subjct was askd to complt two sts of itms quivalnt in difficulty, takn and modifid from th Diffrntial Aptitud Tst. Unlik th writtn portion of our xprimnt, th subjcts wr shown a pattrn on th lft sid of th computr scrn and only on objct on th right hand sid of th computr scrn. Du to th fact that thr was no latralization, subjcts wr givn an unlimitd amount of tim to dtrmin whthr or not th objct on th right was cratd from th pattrn on th lft. Subjcts wr askd to ithr strik th ky labld sam or anothr ky labld diffrnt, ach with a diffrnt hand. As a way of countrbalancing for hand, half of th subjcts wr mad to hit th sam ky with thir lft hands and half of th subjcts wr mad to hit th sam ky with thir right hands. Upon hitting ithr th sam or diffrnt ky, th following qustion would com up on th scrn. Throughout th first st of 20 qustions, th music or whit nois was playd through th hadst into only on ar. Aftr th first st, a notic appard on th computr scrn tlling th subjcts to tak a brak if ncssary, and whn rady, flick th hadphon switch ovr to th opposit sid and procd to th nxt st of qustions. For th subsqunt st of 20 itms th subjct listnd to th sam typ of music or whit nois, but th sound was playd into th ar opposit to th on rciving music during th first st of qustions. Th computr rcordd th numbr of corrct and incorrct answrs as wll as th rspons tims for ach itm. Rsults W hypothsizd that stimulation of th right hmisphr with music prsntd to th lft ar would intrfr with spatial procssing. Our hypothsis also statd that stimulation of th lft hmisphr, with music prsntd to th right ar, and would caus a rduction in intrahmisphric comptition for control of spatial procssing. Our main prdictions, basd on ths hypothss, wr that music playd to th lft ar would dcras prformanc on a spatial task and that music playd to th right ar would nhanc prformanc on a spatial task. W furthr prdictd that Mozart s music would hav a gratr ffct than both jazz and th control condition. For our main prdiction of a music x ar intraction, no significant rsults wr found for rrors or raction tim, nor was thr a main ffct of music or ar. Howvr, a significant intraction was found involving music, handdnss, and ar, F (1, 39)=4.37, p<0.05 (s Figurs 1,2, and 3). A brakdown of th analyss into musical conditions rvald no main ffcts for raction tim in th Mozart group, F(1, 12)=.277, p>0.05, th jazz group, F(1, 11)=.675, p>.05 or th whit nois group, F(1, 11)=.925, p>0.05. Lft handd participants in ach group wr found to display a significant ffct of ar for raction tim, F(2, 9)=4.89, p<0.05, whil right handrs wr not. Upon furthr analysis, th ar diffrncs for th lft handrs in th Mozart group wr found to b statistically significant, F(1, 3)=70.18, p<0.05, with nhancd prformanc whn th music was playd to th right ar. Lft handrs in th jazz condition showd a significant ffct for diffrncs of ar for raction tim, F(1, Colgat Univrsity Journal of th Scincs 143
3)=3.28, p<0.05 in th opposit dirction, with incrasd prformanc whn music was playd to th lft ar. For lft handrs in th control condition, no significant ffcts wr found for diffrncs of ar for raction tim. No significant ffct for diffrncs of ar raction tim, in any of th thr music conditions, wr found for right handrs. No significant main ffct was found for music or ar, and no statistically significant intractions involving music and ar for rrors wr found. Discussion This study tstd prdictions of th bnficial ffcts of music on spatial task prformanc, which wr basd on two compting hypothss. Smith, Chu, and Edmonston (1977) suggst that bimodal stimulation of th right hmisphr with music and tactual stimuli rsults in an intrfrnc ffct that impairs prformanc on a haptic discrimination task. Thrfor, sinc both spatial-tmporal rasoning (Corballis, 1997; Ditunno & Mann, 1990) and procssing of mlodic stimuli (Bvr & Chiarllo, 1974; Thomas & Shucard, 1983) ar primarily functions of th right hmisphr, w prdictd that whn music is dirctd to th lft ar/right hmisphr during spatial tasks, prformanc will b impaird du to comptition within th right hmisphr for its attntional rsourcs. In contrast, Rauschr and Shaw (1995) hypothsiz that Mozart s music facilitats th hmisphric synchronization of cortical firing pattrns involvd in spatial-tmporal task prformanc, thrby nhancing spatial-tmporal rasoning ability. Whil thir study looks at th ovrall ffct of music on both hmisphrs, w mak th assumption in th prsnt study that Mozart can hav th sam ffct on cortical firing pattrns within ach hmisphr individually. In accordanc with this thory, w prdictd that music dirctd to th lft ar/right hmisphr will produc a gratr improvmnt in spatial task prformanc during xposur to Mozart than during xposur to jazz or whit nois. No main ffct of music was found in th prsnt study. Howvr, an intraction among handdnss, music, and ar was found for raction tim. Furthr analysis indicatd that an intraction btwn music and ar occurrd for th raction tims of lft handrs only. W found that lft handd participants in both th Mozart and jazz conditions had significantly diffrnt raction tims dpnding on which ar/hmisphr th music was dirctd to. Participants had a slowr raction tim whn Mozart was playd into th lft ar than whn jazz or whit nois wr playd into th lft ar. Convrsly, participants showd a fastr raction tim whn Mozart was dirctd to th right ar, compard to whn jazz or whit nois wr dirctd to th right ar. Lft handd participants showd a significantly slowr man raction tim whn music was playd into th lft ar in th Mozart condition compard to th whit nois condition. Thy showd a significantly fastr raction tim whn Mozart was playd into th right ar than whn whit nois was dirctd to th right ar. Lft handd participants in th jazz condition, howvr, showd a significantly fastr man raction tim whn music was playd into th lft ar compard to whn whit nois was playd into th lft ar. Participants in th jazz condition also showd a significantly fastr man raction tim whn music was dirctd to th right ar than controls. This was an unxpctd obsrvation sinc w had xpctd th jazz and whit nois conditions to show similar rsults. Whil th dirction of th intraction for th whit nois condition was th sam as that for th jazz condition, thr wr no significant ar diffrncs for th raction tims of controls. Th intraction obsrvd in th Mozart condition coincids with our first prdiction that spatial task prformanc would b impaird rlativ to controls whn music is dirctd to th lft ar/right hmisphr. In accordanc with th hypothsis proposd by Smith, Chu, and Edmonston (1977), intrahmisphric comptition for th sam attntional mchanisms may xplain th obsrvd dcrmnt in spatial task prformanc in th Mozart condition compard to th whit nois condition. Whil this rsult is consistnt with thir findings, nothing conclusiv is stablishd by our rsults sinc w do not know th natur of th brain symmtry among ths lft handd individuals in our study. On th othr hand, it must b takn into considration that lft handd individuals ar known gnrally to hav lss latralization of spatial and linguistic abilitis than right handd individuals. Thus thr may b a gratr tndncy for both crbral hmisphrs to compt for procssing spatial information. By playing music into th hmisphr lss proficint for spatial procssing, w occupy it and prvnt it from intrfring with right hmisphr procssing, thrby rsulting in improvd spatial prformanc. This may account for th improvd prformanc obsrvd whn lft handd individuals rcivd Mozart dirctd to th right ar/lft hmisphr. 144 Colgat Univrsity Journal of th Scincs
Th rsults of this study ar inconsistnt with th prdiction, basd on Rauschr and Shaw s (1995) hypothsis, that whn music is dirctd to th lft ar/right hmisphr thr will b a gratr nhancmnt in prformanc during xposur to Mozart than during xposur to jazz or whit nois. Ths rsarchrs propos that Mozart s music facilitats th cortical firing pattrns of th crbral hmisphrs, in ffct nhancing spatial-tmporal rasoning ability. Th Mozart ffct was not rplicatd in this study, in that an nhancing ffct of Mozart occurrd only whn it was dirctd to th hmisphr not thought to b prdominantly ngagd in spatial procssing. Yt such an ffct was obsrvd whn jazz was dirctd to th lft ar/right hmisphr, suggsting that this musical stimulus may hav intractd with right hmisphr nurons to facilitat th spatial-tmporal rasoning rspons. On th othr hand, thr is th possibility that in our particular sampl of lft handrs, brain organization for spatial functions may hav bn rvrsd with vrbal, latralizd to th lft hmisphr. If this is indd th cas, Rauschr s hypothsis is consistnt with our rsults. In th absnc of indpndnt masurs of latralization pattrns for spatial functions in this study, no dfinitiv conclusions can b drawn. Furthr rsarch rgarding th functional asymmtry of th crbral hmisphrs for spatialtmporal rasoning ability in lft handd individuals would b worthy of invstigation in ordr to xplain th diffrntial rsults obtaind from popl who ar right handd vrsus thos who ar lft handd. Such an invstigation should rplicat this xprimnt only in lft handd individuals in ordr to obtain a largr sampl siz. Futur rsarch may also b intrstd in latralizing spatial stimuli to th right and lft crbral hmisphrs sparatly in lft handd popl, in ordr to dtrmin crbral dominanc for spatialtmporal procssing. In addition, th intraction btwn jazz music, ar, and raction tim is also an intrsting ffct worthy of furthr invstigation. It may b that othr typs of music, in addition to Mozart, affct spatial-tmporal procssing and subsqunt task prformanc for diffrnt rasons. 13 Mozart Condition R a c t I o n T i m 12 11 10 9 8 Lft Ear Right Ear Hand Dominanc Right Lft Ear Figur 1. Raction tim as a function of ar for right and lft handd participants listning to Mozart. Colgat Univrsity Journal of th Scincs 145
Jazz Condition R a c t i o n T i m 13 12 11 10 9 8 7 Lft Ear Right Ear Hand Dominanc Right Lft Ear Figur 2. Raction tim as a function of ar for right and lft handd participants listning to jazz. 146 Colgat Univrsity Journal of th Scincs
Whit Nois Condition R a c t I o n T i m 12.0 11.5 11.0 10.5 10.0 9.5 Hand Dominanc Right 9.0 Lft Ear Right Ear Lft Ear Figur 3. Raction tim as a function of ar for right and lft handd participants listning to whit nois. Colgat Univrsity Journal of th Scincs 147
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