effet du nombre des graphèmes en Anglais - Aix Marseille Université
effet du nombre des graphèmes en Anglais - Aix Marseille Université
effet du nombre des graphèmes en Anglais - Aix Marseille Université
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258App<strong>en</strong>dice IIIHowever, an unsolved question remains with respect of both models : how does the reading system parsethe letter sequ<strong>en</strong>ce into graphemes ? The <strong>du</strong>al-route model suggests that a set of rule correspondances is usedfor the graphemic segm<strong>en</strong>tation. The remaining question here is : which repres<strong>en</strong>tational format or cognitivecode does the reading system use to implem<strong>en</strong>t this set of rules giv<strong>en</strong> that rules belong mainly to high-levelcognitive processes and seem less plausible for fast and automatic perception processes ? Similarly, Plaut etal. (1996) did not specify how does the reading system perform the graphemic segm<strong>en</strong>tation. In their model,input letter strings are parsed into onset-nucleus-coda graphemes by turning on the corresponding graphem<strong>en</strong>o<strong>des</strong>. Thus, it appears that these authors implicitly assume that graphemes are basic units of the readingsystem which leads paradoxically to the conclusion that graphemes are considered in their model as localrepres<strong>en</strong>tations (Grainger &Jacobs, 1998a).A solution to the graphemic segm<strong>en</strong>tation problem can be found in a boxological model proposed byLaberge and Samuel (1974). These authors suggested that <strong>du</strong>ring the acquisition of reading, intermediate readingunits (units situated betwe<strong>en</strong> the letter and word levels) are developped within the reading system. Thefunctional role of these units would be to increase the automaticity and rapidity of skilled reading and to allowprogressively the processing of letter strings as wholes. The establishm<strong>en</strong>t of these intermediate units wouldlikewise be a manner to push the reading system in the direction of an increased parallel processing of writt<strong>en</strong>words. The idea that graphemes could be such intermediate units was already suggested by Gibson, Pick,Osser, & Hammond (1962). Another argum<strong>en</strong>t in favour of this assumption comes from the fact that graphemeshave a functional role with respect to phonological units. Graphemes could thus be viewed in suchcontext as phonographic reading units (Peereman & Cont<strong>en</strong>t, 1997).How does the « reading unit » hypothesis solve the graphemic segm<strong>en</strong>tation problem? If one assumesthat the reading system develops repres<strong>en</strong>tations of intermediate reading units, th<strong>en</strong> the functional segm<strong>en</strong>tationof a letter sequ<strong>en</strong>ce could be done by activating a set of matching intermediate reading units. This solutionis implicitly used in the Plaut et al. model (1996) <strong>des</strong>pite that these authors do not explicitly assume thatgraphemes are reading units or localist repres<strong>en</strong>tations of the reading system. Also, this « reading unit »solution could be a more functionally plausible alternative in order to perform the grapheme-to-phonemeconversion in the Coltheart et al. model (1993).The purpose of the pres<strong>en</strong>t study is to test experim<strong>en</strong>tally the assumption that graphemes are processed asperceptual units by the reading system. Indeed, the psychological validity of graphemes has be<strong>en</strong> assumed bymany models of word recognition <strong>des</strong>pite only few empirical data are available to support such assumption.As a window to explore unitization processes, a large number of studies used the letter detection proce<strong>du</strong>re (fora review, see Healy, 1994). The preliminary idea in these manipulations is that the reading system processparticular groups of letters as wholes or reading units. Therefore, searching for a letter embedded in a readingunit appears costly since subjects have to split the unit into its constitu<strong>en</strong>t letters in order to perform thetask. Letter detection studies reported, for example, missing detections for letters embedded in high frequ<strong>en</strong>cyshort words such as THE (the target letter being E). Since these words are probably processed as wholes bythe reading system, they consequ<strong>en</strong>tly seem to mask the id<strong>en</strong>tification of their constitu<strong>en</strong>t letters (e.g., Corcoran,1966 ; Drewnowski & Healy, 1977).We followed the same logic in the pres<strong>en</strong>t study. Indeed, if graphemes are processed as units by the readingsystem, th<strong>en</strong> detecting a letter embedded in a multi-letter grapheme should be harder than detecting a letterbeing a single-letter grapheme itself. As an illustration, searching for the letter A in the word BEACH (Abeing embedded in the multi-letter grapheme EA -> /i/) should be harder than searching for A in the wordGRASS (A being here a single-letter grapheme).We tested this hypothesis in two experim<strong>en</strong>ts done in English (Experim<strong>en</strong>t 1) and Fr<strong>en</strong>ch (Experim<strong>en</strong>t 2).In both experim<strong>en</strong>ts, we used the same experim<strong>en</strong>tal <strong>des</strong>ign. Subjects were pres<strong>en</strong>ted a target letter followedby a word and had to decide whether or not the letter was in the word. In pres<strong>en</strong>t trials, letters were eitherembedded in a multi-letter grapheme (e.g., A in BEACH) or were equival<strong>en</strong>t to a single-letter grapheme (e.g.,A in GRASS). In addition, we performed a frequ<strong>en</strong>cy manipulation of the words. In half of the graphemeconditions, words were of high frequ<strong>en</strong>cy and for the other half, words were of low frequ<strong>en</strong>cy. This manipulationwas int<strong>en</strong>ded to test whether unitization is pre-lexical as suggested by the reading unit assumption. Theprediction in this case is that if there is any evid<strong>en</strong>ce of a pre-lexical unitization proce<strong>du</strong>re, th<strong>en</strong> letter detectionlat<strong>en</strong>cies should be indep<strong>en</strong>dant of the lexical status of the target word.EXPERIMENT 1ParticipantsParticipants were 21 psychology stud<strong>en</strong>ts from Macquarie University. All were native Australian-Englishspeakers and had normal or corrected to normal vision.Stimuli and ApparatusThe stimulus set was composed of 60 target-pres<strong>en</strong>t trials and 60 target-abs<strong>en</strong>t trials. The 60 target-pres<strong>en</strong>ttrials were divided into four lists of 15 monosyllabic, 5-letter English words (see App<strong>en</strong>dix A). Each list wasmatched betwe<strong>en</strong> items for the target letter and for its position in the word. Two lists were composed of lowfrequ<strong>en</strong>cywords (F < 10 occur<strong>en</strong>ces per million) and two lists of high frequ<strong>en</strong>cy words (F > 50 occur<strong>en</strong>ces permillion). Each frequ<strong>en</strong>cy list was matched betwe<strong>en</strong> items for word frequ<strong>en</strong>cy. Frequ<strong>en</strong>cy was estimated usingthe CELEX frequ<strong>en</strong>cy count (Baay<strong>en</strong>, Piep<strong>en</strong>brock, & van Rijn, 1993). For one list of words in each fre-