Blocking and Learned Attention in Language Acquisition

Blocking and Learned Attention in Language Acquisition Nick C. Ellis (NCELLIS@Umich.Edu) Department of Psychology and English Language Institute, University of Michigan 401 E. Liberty St., Ste. 350, Ann Arbor, MI 48104 USA Abstract devices such as temporal adverbials, prepositional phrases, serialization, and calendric reference, with the grammatical expression of tense and aspect emerging only slowly thereafter, if at all (Bardovi-Harlig, 2000). One likely explanation for this is the salience of the formal cues. Prepositional phrases, temporal adverbs, and other lexical cues to time are quite pronounced in the speech stream. Verbal inflections are not (consider yesterday I walked). Zipf’s (1949) principle of least effort describes how frequent words become shorter with use. Speakers want to minimize articulatory effort and hence encourage brevity and phonological reduction. The more they use the more frequent words, automatization of production causes shortening. The most frequent items of language are the closed class words and grammatical morphemes, hence it is these items that are the least salient in the speech stream and, because shorter words tend to be more homophonous, they are also more ambiguous in their interpretations. The low salience and low reliability of grammatical cues tends to make them less learnable (Ellis, 2006). But salience and reliability affect L1A and L2A alike. There has to be something else which explains the limited endstate of L2A. The classic explanations center upon a critical period for language acquisition, with adult brains being less capable of language learning (perhaps because they no longer have access to universal grammar), or upon social interactional factors (adults are less immersed in the L2, their language development is less scaffolded by their interlocutors). This paper describes experiments exploring a competing line of explanation in terms of standard associative learning effects of ‘learned attention’: blocking, overshadowing, and other effects of transfer and inhibition that shift learners’ attention to language as a result of language experience. Kruschke and Blair (2000) describe the associative learning phenomenon of blocking. Learning that a particular stimulus (A) is associated with a particular outcome (X), makes it harder to learn that another cue (B), subsequently paired with that same outcome, is also a good predictor of it, as schematized in Figure 1. Thus, for example, someone who knows that the rooster’s crowing signals dawn may be less likely to notice that increasing traffic noise can reliably be used as a sign of wake-up-time than is someone who hasn’t been exposed to the animal’s alarm. Blocking is an effect of learned attention. For those who previously learned that A predicts X , B is merely distracting them from a perfectly predictive symptom. To avoid this error-inducing distraction, they shift their attention away from cue B to cue A , and consequently Adult language acquisition typically falls far short of nativelike competence. Various explanations have been proposed for this limited attainment of adults compared to children, including critical periods for language acquisition, sociocultural differences, motivational differences, and restricted input. This paper considers an alternative explanation in terms of the associative learning phenomenon of the attentional blocking of later experienced cues by earlier learned ones. It illustrates this phenomenon in investigations of learned attention in the acquisition of temporal reference in a small subset of Latin under experimental conditions. Within the experiment, early experience of adverbial cues blocked the acquisition of verbal tense morphology, and, contrariwise, early experience of tense blocked later learning of adverbs. There were also long-term language transfer effects: first language speakers of Chinese languages, which do not exhibit verb tense morphology, failed to acquire inflectional cues when adverbial and verbal cues were equally available. Keywords: Second language acquisition; attention; blocking; language learning; transfer; tense morphology; time reference. Cues in First and Second Language Acquisition Languages allow the same idea to be expressed in a variety of ways. Consider time, a concept fundamental to human cognition and action. All languages have rich means to express the position of events in a time line; they variously utilize tense (verbal inflectional morphology, e.g. walked vs. walk), lexical adverbs (e.g. now, next, yesterday, tomorrow), prepositional phrases (in the morning, in the future), serialization (presenting events in their order of occurrence), and calendric reference (May 12, Monday). Any stretch of discourse typically uses a variety of these cues in combination (e.g. yesterday I walked to the university but next Tuesday I’ll ride the bus). Children acquiring their first language (L1) eventually learn all of these constructions for expressing time. Adults learning a second language (L2) naturalistically typically do not. Uninstructed L2A from usage is limited in its end-state, with naturalistic or communicatively-based L2A stabilizing at levels far short of nativelike ability at a ‘Basic Variety’ of interlanguage which, although sufficient for everyday communicative purposes, predominantly comprises just nouns, verbs and adverbs, with closed-class items, in particular grammatical morphemes and prepositions, being rare, if present at all. There is typically no functional inflection: no tense, no aspect, no mood, no agreement, no casemarking, no gender assignment (Klein, 1998). L2 temporal reference is initially made exclusively by use of