Modeling phoneme perception. II: A model of stop consonant discrimination A.J.
van Hessen and M. E. H. Schouten
Research Institutefor LanguageandSpeech (OTS), University of Utrecht,TransIO,3512JK Utrecht, The Netherlands
(Received11February 1991;acceptedfor publication22 May 1992)
Combiningelementsfrom two existingtheoriesof speechsounddiscrimination,dual process theory (DPT) and tracecontexttheory (TCT), a new theory,calledphonemeperception theory,is proposed,consisting of a long-termphonemememory,a context-coding memory, and a tracememory,eachwith its own time constants.This theory is testedby meansof stopconsonantdiscrimination data in which interstimulus interval (ISI; valuesof 100, 300, and
2000 ms) is an importantvariable.It is shownthat discriminationin which labelingplaysan importantpart (2IFC and AX betweencategory)benefitsfrom increasedISI, whereas . discriminationin which only sensorytracesare compared(AX within category),decreases with increasingISI. The theoryis alsotestedon speechdiscriminationdata from the literature in which ISI is a variable [ Pisoni,J. Acoust. Soc.Am. 36, 277-282 ( 1964); Cowan and Morse, J. Acoust.Soc.Am. 79, 500-507 (1986) ]. It is concludedthat the numberof parametersin tracecontexttheoryis not sufficientto accountfor mostspeech-sound discriminationdata and that a few additionalassumptions are needed,suchas a form of sublabeling,in which subjects encodethe qualityof a stimulusasa memberof a category,and which requiresprocessing time.
PACS numbers: 43.71.An, 43.71.Es, 43.66.Ba
INTRODUCTION
In this secondpaperof our serieson modelingphoneme perceptionwe want to proposea new theory of phoneme perception(i.e., of subjects'behaviorin variousspeechperceptionexperiments).This theoryis to a very greatextenta new combination of elements from various older theories,
mostnotablyfrom tracecontexttheory (TCT) asadaptedto speechperceptionby Macmillan et al. (1977, 1987, 1988), andfrom dual processtheory (DPT) by Fujisakiand Kawashima ( 1971). The new phonemeperceptiontheory (PPT) consists of four "stages,"eachof whichistreatedasa source of variance:( 1) Spectralanalysis,which introduces"sensory variance;" (2) labeling (absent from TCT; in DPT terms:long-termmemory for phonemeboundary), which introduces"labelingvariance;" (3) contextcoding (absent from DPT ), which introduces"context variance;" (4) trace
coding (in DPT terms: short-term memory for timbre), which introduces
"trace variance."
All thesestagesaremoreor lessself-explanatory, except perhapsthe TCT conceptof contextcoding,accordingto which stimuli are identifiedand discriminatedagainstthe backgroundof the total rangeof stimuli presentedin an experimentalsession.If in eachtrial stimuli are chosenrandomly from a particular range, stimulusuncertaintyis a function of the size of the range:the larger the range, the lowerthe resolution.This hasbeena regularfindingin intensity resolutionexperimentsinvolvingpure tones.Braida et al. (1984) observedan additional effectof contextcoding: stimuliwereresolvedbetterif they werecloserto the edgesof 1856
the range.Apparently, subjectsusethe extremestimuli as anchorpointsfor their internalrepresentation of the range. Macmillan et al. ( 1987, 1988) seizedon this conceptto introducea long-termmemorycomponentinto their theory: They extendedcontextcodingby includingsomethinglike a permanentcontext,in which phonemesare representedas anchors.In this view, phonemecategoriesare storedin a context-coding type of memory,and are thereforesubjectto rangeeffects.DPT, on the otherhand,claimsthat phoneme labelingis autonomousand dominant:phonemesare stored in a separatelong-termphonemememory,which doesnot introducerangeeffects.Apart from theserangeeffects,the differencesbetween the two theories are relatively small, since"labeling"and "permanent-context coding"are otherwise virtually synonymous:A subjectwho useshis longterm memoryfor discriminationrefersthe stimulito his permanent context,which consistsof the phonemeshe hears aroundhim all the time. This permanentcontextis always thereanddoesnot dependonstimulusrangeor experimental paradigm.(It thereforeplaysan importantpart in everyexperiment,evenin fixed discriminationwhere,accordingto TCT, sensoryfactorsare, in practice,the only sourceof variance. )
It shouldbe clear that, althoughexperimentalcontext andpermanent,long-termcontextarenot the same,they can be made to coincideby usinga stimuluscontinuumwhich consistsof natural speechsoundsand which hasend points that are convincingversionsof someof the phonemesthat one hears around one all the time.
J. Acoust.Soc. Am. 92 (4), Pt. 1, October 1992 0001-4966/92/101856-13500.80
¸ 1992 AcousticalSocietyof America
1856
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 141.209.100.60 On: Sun, 21 Dec 2014 00:21:17
In our previouspaper (Schoutenand Van Hessen, 1992a)we attemptedto setoffthe two theoriesagainsteach otherby performingwhat we hopedwouldbe somecrucial
van Hessen and M. E. H. Schouten
Research Institutefor LanguageandSpeech (OTS), University of Utrecht,TransIO,3512JK Utrecht, The Netherlands
(Received11February 1991;acceptedfor publication22 May 1992)
Combiningelementsfrom two existingtheoriesof speechsounddiscrimination,dual process theory (DPT) and tracecontexttheory (TCT), a new theory,calledphonemeperception theory,is proposed,consisting of a long-termphonemememory,a context-coding memory, and a tracememory,eachwith its own time constants.This theory is testedby meansof stopconsonantdiscrimination data in which interstimulus interval (ISI; valuesof 100, 300, and
2000 ms) is an importantvariable.It is shownthat discriminationin which labelingplaysan importantpart (2IFC and AX betweencategory)benefitsfrom increasedISI, whereas . discriminationin which only sensorytracesare compared(AX within category),decreases with increasingISI. The theoryis alsotestedon speechdiscriminationdata from the literature in which ISI is a variable [ Pisoni,J. Acoust. Soc.Am. 36, 277-282 ( 1964); Cowan and Morse, J. Acoust.Soc.Am. 79, 500-507 (1986) ]. It is concludedthat the numberof parametersin tracecontexttheoryis not sufficientto accountfor mostspeech-sound discriminationdata and that a few additionalassumptions are needed,suchas a form of sublabeling,in which subjects encodethe qualityof a stimulusasa memberof a category,and which requiresprocessing time.
PACS numbers: 43.71.An, 43.71.Es, 43.66.Ba
INTRODUCTION
In this secondpaperof our serieson modelingphoneme perceptionwe want to proposea new theory of phoneme perception(i.e., of subjects'behaviorin variousspeechperceptionexperiments).This theoryis to a very greatextenta new combination of elements from various older theories,
mostnotablyfrom tracecontexttheory (TCT) asadaptedto speechperceptionby Macmillan et al. (1977, 1987, 1988), andfrom dual processtheory (DPT) by Fujisakiand Kawashima ( 1971). The new phonemeperceptiontheory (PPT) consists of four "stages,"eachof whichistreatedasa source of variance:( 1) Spectralanalysis,which introduces"sensory variance;" (2) labeling (absent from TCT; in DPT terms:long-termmemory for phonemeboundary), which introduces"labelingvariance;" (3) contextcoding (absent from DPT ), which introduces"context variance;" (4) trace
coding (in DPT terms: short-term memory for timbre), which introduces
"trace variance."
All thesestagesaremoreor lessself-explanatory, except perhapsthe TCT conceptof contextcoding,accordingto which stimuli are identifiedand discriminatedagainstthe backgroundof the total rangeof stimuli presentedin an experimentalsession.If in eachtrial stimuli are chosenrandomly from a particular range, stimulusuncertaintyis a function of the size of the range:the larger the range, the lowerthe resolution.This hasbeena regularfindingin intensity resolutionexperimentsinvolvingpure tones.Braida et al. (1984) observedan additional effectof contextcoding: stimuliwereresolvedbetterif they werecloserto the edgesof 1856
the range.Apparently, subjectsusethe extremestimuli as anchorpointsfor their internalrepresentation of the range. Macmillan et al. ( 1987, 1988) seizedon this conceptto introducea long-termmemorycomponentinto their theory: They extendedcontextcodingby includingsomethinglike a permanentcontext,in which phonemesare representedas anchors.In this view, phonemecategoriesare storedin a context-coding type of memory,and are thereforesubjectto rangeeffects.DPT, on the otherhand,claimsthat phoneme labelingis autonomousand dominant:phonemesare stored in a separatelong-termphonemememory,which doesnot introducerangeeffects.Apart from theserangeeffects,the differencesbetween the two theories are relatively small, since"labeling"and "permanent-context coding"are otherwise virtually synonymous:A subjectwho useshis longterm memoryfor discriminationrefersthe stimulito his permanent context,which consistsof the phonemeshe hears aroundhim all the time. This permanentcontextis always thereanddoesnot dependonstimulusrangeor experimental paradigm.(It thereforeplaysan importantpart in everyexperiment,evenin fixed discriminationwhere,accordingto TCT, sensoryfactorsare, in practice,the only sourceof variance. )
It shouldbe clear that, althoughexperimentalcontext andpermanent,long-termcontextarenot the same,they can be made to coincideby usinga stimuluscontinuumwhich consistsof natural speechsoundsand which hasend points that are convincingversionsof someof the phonemesthat one hears around one all the time.
J. Acoust.Soc. Am. 92 (4), Pt. 1, October 1992 0001-4966/92/101856-13500.80
¸ 1992 AcousticalSocietyof America
1856
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 141.209.100.60 On: Sun, 21 Dec 2014 00:21:17
In our previouspaper (Schoutenand Van Hessen, 1992a)we attemptedto setoffthe two theoriesagainsteach otherby performingwhat we hopedwouldbe somecrucial
