5 General Discussion
5.1 Representation of Regular Stem Allomorphy
The first part of the dissertation investigated derivation employing regular stem allomorphy in English and German. We conducted a series of word list and sentence context experiments with British and German subjects. The word list experiments investigated the processing of complex words and nonwords in isolation with a superimposed linguistic task (lexical decision task) or with a memory task. The sentence context experiments explored lexical retrieval and processing of complex words and nonwords in a biasing context. The series of studies was finalized with a pilot experiment conducted with low-proficient L2 learners of German. The pilot experiment investigated the acquisition of a morphosyntactic rule in line with Ullman’s declarative/procedural model (Ullman, 2001a, 2001b, 2004). We planned to observe the transition from the reliance on the declarative memory in the application of a morphosyntactic rule to the reliance on the procedural memory.
The objective of the word list experiments was the determination of how regular stem allomorphs were listed in the English and German mental lexicons.
We hypothesized that regular phonological stem variants shared a lexical entry.
To test this hypothesis, we studied the error-detection mechanisms triggered by three violation conditions, viz. *ser[i:]nity/*Stärkung (RD), *ser[aɪ]nity/*Sturkung (UD), and *seromity/*Stögung (NC), in comparison with the real word condition serenity/ Stärkung (W). We argued that a unified representation of regular stem allomorphs would allow the structural repair of the RD items that were made up by omitting TSS and umlaut. Therefore, the error-detection mechanisms triggered
by the RD items should differ from those evoked by the complete/irreparable nonword conditions. Separate listing of the regular stem allomorphs would result in a similar brain response pattern for all violation conditions due to the impossibility of structural repair. The results of the word list experiments showed that RD items consistently elicited violation-related brain responses qualitatively distinct from the other conditions. Thus, the lexical decision task experiments in both groups revealed a graded N400 effect of the type W<RD<UD=NC. The violation of TSS in the British memory task experiment evoked a PMN effect in the early processing stages and LPN in the late processing stages. The violation of umlaut in the German memory task experiment elicited a LAN effect. The result pattern of the word list experiments presented supporting evidence for our hypothesis that regular stem allomorphs share a mental lexicon entry. The unique status of the RD items was based on the possibility of structural repair of these nonwords. We argued that the access to the shared representation enabled structural repair of the morphophonological or morphosyntactic rule violations.
We proposed that a unified representation of the regular stem allomorphs should consist of an abstract morpheme with a set of morphophonological surface form rules and morphosyntactic combinatory rules
The structural repair process as revealed by the attenuated N400 effect, on the one hand, and PMN/LPN and LAN, on the other, demonstrated that transparent morphological relations were represented in the mental lexicon. This finding contradicted the proposition of the Full Listing Hypothesis (Butterworth, 1983) that relations between words and word forms should be represented by means of a fast associative network. Following the Full Listing Hypothesis, the phonological/orthographic overlap between the existing words and the RD and UD conditions would have elicited similar brain responses. Without the storage of morphological information it would have been impossible to assess the quality of deviation of the RD and UD items from the stored standard. Therefore, both – morphosyntactic and purely phonological – violation conditions would have been qualified as nonwords evoking similar brain responses. The present pattern of results demonstrated that full listing did not hold for the semantically and morphologically transparent complex words. Our findings also contradicted the Parallel-distributed processing models (Rumelhart & McClelland, 1986;
Seidenberg & Gonnerman, 2000). We demonstrated that morphological relationship influenced the lexical retrieval process as revealed by the difference between reparable and irreparable conditions. In contrast, the PDP models
assumed that the relationship between morphemes did not influence further processing steps.
In the present thesis we adopted the view that semantically and morphologically transparent complex words were subject to obligatory morphological decomposition (Taft & Forster, 1975, 1976). Contrary to the Full Listing Hypothesis and the PDP, the model by Taft and Forster (1975, 1976) required prelexical decomposition of all morphologically complex words.
According to this model, the detection of an affix in an affixed word helps to identify the stem morpheme. Although the present results were in favor of the affix stripping, they were insufficient to provide supporting evidence for the full morphological decomposition regardless of the semantic transparency as proposed by Taft and Forster (1975, 1976).
According to the Parallel Dual-Route model proposed by Schreuder and Baayen (1995), high-frequency words were accessed directly as whole units, while low-frequency words were recognized via their morphemes. The authors claimed that morphological decomposition decelerated lexical retrieval and was resorted to only in case of novel or unknown words. The W condition of the present series of studies employed complex words with relatively high frequency of occurrence, while the nonword items had a zero frequency of occurrence.
Nevertheless, we did not observe any latency shifts indicative of the acceleration or deceleration of lexical retrieval. Therefore, the present pattern of results could not be regarded as supporting the Parallel Dual-Route model. Dual-Mechanism models (Pinker, 1999; Clahsen, 1999; Friederici et al, 1993; Marslen-Wilson &
Tyler, 1997, 1998, 2003, Ullman, 2001, Pinker and Ullman, 2002) posit that the mechanism of lexical access depends on the type of morphological composition.
Regular inflection forms were subject to morphological decomposition, while irregular inflection forms and derived words were subject to full listing. The present pattern of results could support Dual-Mechanism models if the notion of regularity were extended to regular phonological alternations.
The present pattern of results supported the accounts by Marslen-Wilson et al. (1994), Wiese (1996) and Scharinger et al. (2009, 2010) having demonstrated that regular stem allomorphs should be represented by a single abstract morpheme with a set of morphophonological and morphosyntactic rules.
Marslen-Wilson et al. (1994) and Scharinger et al. (2010) regarded the unified representation as based on the stem vowel underspecification. In contrast, Wiese (1996) considered umlaut as a phonological rule that was triggered only if a stem morpheme had a floating feature [FRONT]. Although we did not intend to validate
Marslen-Wilson et al.’s (1994), Wiese’s (1996) and Scharinger et al.’s (2009, 2010) accounts, the present results showed that regular stem vowel alternations should be governed by the intrinsic ability of the stem vowel to alternate.
Summarized, the results of the first part of the present thesis provided evidence for (i) the obligatory morphological decomposition of semantically transparent complex words (Taft & Forster, 1975, 1976; Taft & Hambly, 1985;
Taft & Kougious, 2004); (ii) a unified representation of regular stem allomorphs;
(iii) a similar representation of regular stem allomorphs in English and German (W.D. Marslen-Wilson et al., 1994; Scharinger, 2009; Scharinger et al., 2010).
Though we demonstrated that semantically transparent complex words were morphologically segmented, we did not claim that all word forms regardless of their semantic and morphological transparency are stored in a decomposed manner.