Vocabulary Size Is a Key Factor in Predicting Second Language Lexical Encoding Accuracy.

Danielle Daidone,Isabelle Darcy

doi:10.3389/fpsyg.2021.688356

Abstract

This study investigates the relationship between the accuracy of second language lexical representations and perception, phonological short-term memory, inhibitory control, attention control, and second language vocabulary size. English-speaking learners of Spanish were tested on their lexical encoding of the Spanish /ɾ-r/, /ɾ-d/, /r-d/, and /f-p/ contrasts through a lexical decision task. Perception ability was measured with an oddity task, phonological short-term memory with a serial non-word recognition task, attention control with a flanker task, inhibitory control with a retrieval-induced inhibition task, and vocabulary size with the X_Lex vocabulary test. Results revealed that differences in perception performance, inhibitory control, and attention control were not related to differences in lexical encoding accuracy. Phonological short-term memory was a significant factor, but only for the /r-ɾ/ contrast. This suggests that when representations contain sounds that are differentiated along a dimension not used in the native language, learners with higher phonological short-term memory have an advantage because they are better able to hold the relevant phonetic details in memory long enough to be transferred to long-term representations. Second language vocabulary size predicted lexical encoding across three of the four contrasts, such that a larger vocabulary predicted greater accuracy. This is likely because the acquisition of more phonologically similar words forces learners’ phonological systems to create more detailed representations in order for such words to be differentiated. Overall, this study suggests that vocabulary size in the second language is the most important factor in the accuracy of lexical representations.

Highlights

Models of second language (L2) speech perception have typically focused on the effect of the first language (L1) at the level of phonetic or phonological categories (e.g., Flege, 1995; Best and Tyler, 2007), with the implicit assumption in the field being that the accuracy of category perception directly translates to the accuracy of these sounds in the lexicon, that is, of lexical representations
This study used a lexical decision task to investigate lexical encoding accuracy, an oddity task to examine perception of the contrasts appearing in the lexical task, a serial nonword recognition task to investigate phonological short-term memory (PSTM), a retrieval-induced inhibition task to measure inhibitory control, a flanker task to investigate attention control, and an X_Lex vocabulary test to estimate Spanish vocabulary size, all described in detail below
While perception was predicted to have a large effect on lexical encoding accuracy, surprisingly there was no effect for any of the analyses

Summary

Introduction

Models of second language (L2) speech perception have typically focused on the effect of the first language (L1) at the level of phonetic or phonological categories (e.g., Flege, 1995; Best and Tyler, 2007), with the implicit assumption in the field being that the accuracy of category perception directly translates to the accuracy of these sounds in the lexicon, that is, of lexical representations. There must be other factors at play that influence learners’ ability to encode the sounds of L2 words in long term memory Identifying these factors is important theoretically, as examining such individual differences can give a window into the mechanisms necessary for the establishment of lexical representations. Simonchyk and Darcy (2017) examined the relationship between perception and lexical encoding for plain versus palatalized consonants for English-speaking learners of Russian at different levels of proficiency They found that there was no relationship between intermediate learners’ error rates in an ABX perception task and their error rates in an auditory wordpicture matching task. A learner’s perception ability alone is not sufficient to predict the accuracy of their lexical representations

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