The Mental Representation of Inflected Words: An Experimental Study of Adjectives and Verbs in German

The authors investigate how morphological relationships between inflected word forms are represented in the mental lexicon, focusing on paradigmatic relations between regularly inflected word forms and relationships between different stem forms of the same lexeme. We present results from a series of psycholinguistic experiments investigating German adjectives (which are inflected for case, number, and gender) and the so-called strong verbs of German, which have different stem forms when inflected for person, number, tense, or mood.

Evidence from three lexical-decision experiments indicates that regular affixes are stripped off from their stems for processing purposes. It will be shown that this holds for both unmarked and marked stem forms. Another set of experiments revealed priming effects between different paradigmatically related affixes and between different stem forms of the same lexeme.

We will show that associative models of inflection do not capture these findings, and we explain our results in terms of combinatorial models of inflection in which regular affixes are represented in inflectional paradigms and stem variants are represented in structured lexical entries. We will also argue that the morphosyntactic features of stems and affixes form abstract underspecified entries. The experimental results indicate that the human language processor makes use of these representations.*

1. Morphology and the mental lexicon

Much psycholinguistic research has been devoted to the question of whether there is any correspondence between the linguistic structure of a morphologically complex word and the way it is segmented by the speaker-hearer during on-line production and comprehension. Are morphologically complex words that have stem + affix representations (e.g. derived words such as govern-ment or regularly inflected words such as walk-ed) computed via their constituent morphemes? Are irregularly inflected words that cannot be formed through affixation stored unanalyzed in the mental lexicon?

Experimental studies have produced conflicting answers to these questions. Two broad views can be distinguished. Associative models of morphological processing claim that the morphological structure of words plays no role in the way they are produced or perceived and that words are listed as full forms in memory. The key idea is that all morphological patterns, including those that can be decomposed into stems, roots, and affixes, are derived from a network of associative relations. Connectionist networks of inflection (Rumelhart & McClelland 1986, MacWhinney &Leinbach 1991, Plunkett & Marchman 1993, mong others) can be seen as modern implementations of associative models of language. In contrast to this, other researchers have argued that the mental lexicon encodes morphological structure and that this information plays a role in comprehension and production. Specifically, the language processor is said to make use of morphological decomposition for dealing with morphologically complex words, in addition to full-form representations (e.g. Laudanna & Burani 1985, 1995, Frauenfelder & Schreuder 1992, Schreuder & Baayen 1995, Pinker & Prince 1991).

A related question that has received much less attention from psycholinguists is how morphological relationships between inflected word forms are represented in the mental lexicon. Consider, for example, the inflected adjectives from German in 1a, which are marked for case, number, and gender, and the inflected verb forms in 1b, which are marked for person, number, and tense.

(1)

a.	wild-es	wild-em	wild-er
	‘wild-nom.neut.sg.’	‘wild-dat.masc.sg.’	‘wild-nom.masc.sg.’
b.	(ich) werf-e	(du) wirf-st	(sie) warf-en
	‘(I) throw-1sg.pres.’	‘(you) throw-2sg.pres.’	‘(they) throw-3pl.pret.’

Both adjectival and verbal agreement affixation are highly regular: -s, -m, and -r can be attached to any adjective and -e, -st, and -n to any verb. Exceptions are a few high frequency forms, such as the suppletive form bin (‘am’ 1 sg. pres.) and first and third person singular present tense forms of verbs such as müssen ‘to be able to’, dürfen ‘to be allowed to’, sollen ‘to be about to’, which (like their corresponding preterite forms) do not have a person/number agreement suffix: ich/er muss, darf, soll ‘I/he must, may shall’. Thus, decompositional accounts of morphological processing predict that all the...