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MEASURING PHONOLOGICAL SHORT-TERM MEMORY,

APART FROM LEXICAL KNOWLEDGE

by

Tamara Eva Kornacki

A thesis submitted in conformity with the requirements for the degree of Master of Arts

Department of Human Development and Applied Psychology Ontario Institute for Studies in Education

University of Toronto

! Copyright by Tamara Eva Kornacki 2011

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MEASURING PHONOLOGICAL SHORT-TERM MEMORY, APART FROM LEXICAL KNOWLEDGE

Master of Arts Tamara Eva Kornacki

Human Development and Applied Psychology University of Toronto

Abstract

The current research examined whether nonword repetition (NWR) tasks, designed to measure

phonological short-term memory, are also influenced by familiarity with lexical representation of

a given language. In Study 1, children with and without exposure to Hebrew were administered a

NWR task based on the Hebrew language structure (HNWR). On the HNWR, participants with

Hebrew exposure significantly outperformed participants who had no familiarity with any

Semitic language. This indicates that long-term phonological and lexical knowledge can be used

to aid NWR performance. Study 2 investigated whether a NWR task based on a foreign language

could minimize the lexicality effect. English speaking undergraduate students rated the less

familiar HNWR task to be lower in wordlikeness than English-like NWR tasks. These findings

demonstrate that regardless of language background a NWR task based on an unfamiliar

language structure is a more valid measure of the phonological processing skills required for

vocabulary acquisition.

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Acknowledgements

I am indebted to a number of people for their assistance with this thesis. First and

foremost, I would like to thank Dr. Esther Geva for serving as my research supervisor and

mentor. Her thoughtful guidance has steered my scientific growth and conceptual thinking. I

must also acknowledge Dr. Geva for supplying archival data from the ESL at Risk and Hebrew

Immersion projects. Dr. Fataneh Farnia is also gratefully acknowledged for her technical

assistance. In addition, I am thankful to Dr. Xi Chen for the honour of serving on my thesis

committee. Finally, to my colleagues Christie Fraser, Sarah Gray, Norman Himmel, Adrian

Pasquarella, Dana Shafman, and Sharon To I extend my deepest appreciation for your daily

encouragement and wise counsel.

Support for the collection of this data was provided to Dr. Geva by the Social Sciences

and Humanities Research Council of Canada.

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Table of Contents

Introduction

Overview ………………………………………………………….. 1

Phonological Short-term Memory…………………………………. 1

Nonword Repetition…………………………………………………. 2

The Nature of the Relationship Between Nonword Repetition and Vocabulary…...

3

Phonological memory hypothesis of nonword repetition.............. 3

The linguistic hypothesis of nonword repetition…....................... 4

Moving toward a more integrated model of nonword repetition... 6

Rationale and Objectives of the Present Study……………………… 7

Study 1: The Effect of Hebrew Language Exposure on a Hebrew-like

Nonword Repetition Task

Method…………………………………………………………….. 10

Participants………………………………………………………. 10

Materials…………………………………………………………. 11

Hebrew-Like Nonword Repetition Task (HNWR)…………… 11

Nonverbal ability……………………………………………… 11

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Procedure…………………………………………………………. 12

Results………………………………………………………………… 12

Study 2: The Wordlikeness of English-like and Hebrew-like Nonword

Repetition Tasks

Method……………………………………………………………… 15

Participants……………………………………………………….. 15

Materials………………………………………………………….. 15

Wordlikeness Questionnaire …………………………………. 15

Nonword repetition tasks …………………………………….. 16

Procedure………………………………………………………… 16

Results………………………………………………………………. 17

Discussion

Summary of Findings…………………………………………………. 19

Limitations……………………………………………………………. 22

Implications…………………………………………………………… 23

References……………………………………………………………….. 24

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List of Figures

Figure 1. Mean raw score on HNWR task as a function of language group……………………………………………………………………...

13

Figure 2. Mean raw score on Wordlikeness Questionnaire for nonword repetition tasks……………………………………………………………

18

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List of Appendices

Appendix A: Materials

Hebrew-like Phonological Short- term Memory……………… 28

Adapted Version of Children’s’ Test of Nonword Repetition …29

Wordlikeneness Questionnaire ………………………………...30

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List of Abbreviations

CNWR Comprehensive Test of Phonological Processing, Nonword Repetition

ESL English as second language

EL1 English as first language

GNWR Adapted Students’ Test of Nonword Repetition

HNWR Hebrew-like nonword repetition task

L1 First language

L2 Second language

NWR Nonword repetition

PSTM Phonological short- term memory

WM Working memory

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Introduction

Overview

The following thesis examines the role of long-term lexical knowledge in the

measurement of phonological short-term memory. The thesis will begin by reviewing current

knowledge on nonword repetition (NWR) tasks designed to measure phonological short-term

memory, before examining the relation between NWR tasks and lexical knowledge. Finally,

research will be presented to establish whether a NWR task based on an unfamiliar language

structure minimizes the ability to rely on stored knowledge about the phonological structure of a

given language. Finally, the thesis will conclude with a discussion of the current findings and

their implications for researchers and clinicians.

Phonological Short-term Memory

Working memory (WM) refers to a limited capacity system that temporarily stores and

manipulates information while we perform complex cognitive activities (Baddeley, 2003a).

Baddeley’s multicomponent model proposes that WM has three components, the central

executive, the phonological loop and the visuospatial sketchpad (Baddeley & Hitch, 1974). The

central executive is a control system that is assisted by two storage systems, including the

phonological loop, which stores sounds and language, and the visuospatial sketchpad, which

stores visual spatial material (Baddeley, 2003b).

The function of the phonological loop is to temporarily maintain unfamiliar phonological

forms while long-term representations are being established (Baddeley, Gathercole & Papagno,

1998). The phonological loop, also known as phonological short-term memory (PSTM), is

located in the left temporoparietal region of the brain. It is composed of two subcomponents, the

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phonological store, which is found in the Brodman area 44 region, and the articulatory rehearsal

system, which is situated in Broca’s area (Baddeley, 2003b). When auditory information is

presented (e.g. you are given a phone number but don’t have a pen to write it down), speech

sounds are analyzed and fed into the phonological storage system, where the memory traces

remain for a few seconds before they decay. To offset decay, the information being held in the

phonological store is fed into the articulatory rehearsal system, where it can be rehearsed sub-

vocally (e.g. repeating the phone number in your mind) and reactivated in the phonological store

(Baddeley et al, 1998). While the phonological store does not appear to be influenced by

previous language knowledge, the articulatory system may depend on pre-existing

morphological knowledge of a given language (Baddeley, 2003b).

Nonword Repetition

During the process of language development, infants instinctively attempt to mimic the

words of others. Children’s ability to repeat novel multi-syllabic words is an important predictor

of language learning ability (Baddeley et al, 1998). Therefore, researchers and clinicians are

interested in individual differences in the capacity to accurately repeat unfamiliar words. This

ability is most commonly measured using nonword repetition (NWR) tasks wherein participants

listen to phonologically unfamiliar words (e.g., chaseedoolid) on a tape, and are asked to repeat

them back as accurately as possible.

Nonword repetition tasks are interpreted as a measure of PSTM because the phonological

structure of the nonword is presumed to be novel and therefore, not to have a corresponding

entry in long-term lexical memory. Consequently, in order to accurately repeat the nonword

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several moments after it is presented, one must temporarily maintain the novel sound sequence in

the phonological loop (Gathercole, Willis, Emslie, & Baddeley, 1992).

The Nature of the Relationship Between Nonword Repetition and Vocabulary

Across studies, individual differences in children’s nonword repetition performance has

been found to be positively associated with vocabulary knowledge (r=.22-.53; Gathercole &

Adams, 1993, 1994; Gathercole & Baddeley, 1989; Gathercole, Hitch, Service, & Martin,1997;

Gathercole, Willis, & Baddeley, 1991; Gathercole et al., 1992; Michas & Henry, 1994). A

wealth of evidence demonstrates that nonword repetition is closely related to vocabulary

acquisition; however, the nature of this association has been subject to some debate, as explored

in the following sections.

Phonological memory hypothesis of nonword repetition. The phonological memory

hypothesis proposes that a person’s capacity to repeat what they hear helps them to learn new

words (Gathercole, Willis, Emslie, & Baddeley, 1991). A wealth of evidence demonstrates that

the phonological loop plays a vital role in the acquisition of native language vocabulary. Studies

have consistently identified a causal relationship between PSTM and subsequent vocabulary

when examined longitudinally. For instance, Gathercole and Baddeley (1989) found that

nonword repetition scores at age 4 significantly predicted vocabulary skills one year later, even

after controlling for initial vocabulary knowledge. Similar findings have also been demonstrated

in experimental simulations of vocabulary learning. Gathercole and Baddeley (1990) taught

phonologically unfamiliar names of toy animals to children with either high or low NWR ability

(who were matched on nonverbal ability). They found that the low NWR group was significantly

lower than the high NWR group in word learning performance. A study by Service (1992) also

demonstrated that NWR ability (age M=4.1 years) predicted foreign language learning capacity

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among eighteen Finnish children (learning English as a second language (L2). Furthermore,

neuropsychological evidence shows that individuals with PSTM deficits arising from brain

damage have difficulties acquiring the vocabulary of a new language (Baddeley, Papagno, &

Vallar, 1988). Taken together, these findings from developmental and neuropsychological

research support the argument that PSTM plays a vital role in vocabulary development by

enabling us to encode unfamiliar sequences of phonemes (Baddeley et al, 1998).

The linguistic hypothesis of nonword repetition. The linguistic hypothesis provides an

alternative explanation for the nature of the link between NWR and vocabulary acquisition

(Snowling, Chiat, & Hulme, 1991). According to this view, pre-existing lexical knowledge can

be used to support the repetition of nonwords by increasing familiarity to the sublexical units

embedded within nonwords (Gathercole et al., 1991).

The lexical influence on nonword repetition is demonstrated by three key phenomena.

Firstly, the link between PSTM and vocabulary is typically strongest during the early stages of

language acquisition when we can rely less on our existing lexicon (Masoura & Gathercole,

2005). For instance, Gathercole and colleagues found that the robust relationship between PSTM

and vocabulary development at 4 to 5 years was no longer significant at 8 years (Gathercole et

al., 1992). These findings suggest a developmental shift; as vocabulary knowledge grows,

children can rely more on long-term phonological knowledge to supplement short-term

phonological storage when learning unfamiliar words.

Secondly, the phenomenon of wordlikeness demonstrates that previous vocabulary

knowledge may bolster performance on nonword repetition tasks. Even though nonwords are

nonlexical, their sublexical units may not always be entirely novel. Wordlikeness refers to the

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extent that nonwords resemble the phonotactic structures of a particular language. Studies have

shown that performance on NWR tasks is influenced by word-likeness to one’s native language,

with better accuracy for words rated high in wordlikeness than words rated low in word-likeness

(Gathercole, 1995). Nonwords high in word-likeness may facilitate NWR recall by allowing

individuals to chunk strings of sounds into familiar morphological units that are already stored in

long-term memory. Indeed, Gathercole (1995) demonstrated a stronger association between

vocabulary knowledge and subsequent performance on NWR items high in wordlikeness;

however no such association was found for vocabulary and less wordlike nonwords. These

findings suggest that children are better able to draw on their vocabulary knowledge when

repeating highly wordlike nonwords. Thus, it seems that wordlikeness should reduce the

sensitivity of NWR tasks in assessing the constraints of the phonological loop because they

facilitate increased reliance on long-term lexical knowledge.

Additional support for the linguistic hypothesis comes from studies showing that

nonwords which are similar to the phonotactic structure of one’s native language are repeated

with greater accuracy than nonwords based on a non-native language. Masoura and Gathercole

(1999) found that 40 Greek children (mean age 11.2 years) who were learning English as an L2

performed better on a NWR task based on Greek language structure than an NWR task based on

English language structure. They had been learning English for approximately 3.5 years. These

findings indicate that performance is enhanced on NWR tasks constructed from the morphology

of one’s native language compared to NWR tasks based on one’s non-native, although highly

familiar, second language. Relatedly, an NWR measure based on foreign nonwords, such as

Hebrew, appears to better predict concurrent and longitudinal vocabulary acquisition amongst

children with English as a Second Language and English as a First Language, compared to an

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English-like NWR (Geva & Farnia, 2010, Kornacki, Geva, Farnia, & Shafman, 2011). Thorn

and Gathercole (1999) administered an English-like NWR and a French-like NWR to 45 children

with varying levels of French vocabulary knowledge (English monolinguals, native English with

French as L2, and native bilinguals; mean age 5.7 years). They found that performance on each

NWR task reflected their levels of vocabulary knowledge in the corresponding test language.

More specifically, the monolinguals and French second-language learners were more accurate at

repeating English nonwords than French nonwords; however, bilingual children were equally

accurate in repeating French-like and English-like nonwords. Increasing familiarity with the

French language and its sublevel components enabled the children to better perform on the NWR

task. Taken together, the linguistic hypothesis of NWR performance is supported by a

developing body of research examining non-native NWR, wordlikeness, and developmental

differences in NWR.

Moving toward a more integrated model of nonword repetition. Given emerging

evidence supporting the linguistic hypothesis, the view that PSTM contributes to vocabulary

acquisition in a unidirectional manner seems to be overly simplistic. In the early stages of

language acquisition, there does seem to be a causal, unidirectional relationship between PSTM

and vocabulary development, but over time it seems that this relationship becomes more

reciprocal (Baddeley, 2003b). This shift can be attributed to the fact that as vocabulary

knowledge increases, it can be used more readily to aid the articulatory system in maintaining

novel sounds in the phonological loop. Although the phonological loop is often seen as a passive

storage device, it appears to operate interactively with permanent knowledge. Thus, the lexicality

effect seems to arise from the process of redintegration, where activated lexical representations

are used in the articulatory system to aid retrieval of incomplete information held in the

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phonological store (Gathercole, Frankish, Pickering, & Peaker, 1999; Hulme et al., 1997).

Therefore, it appears to be more likely that current nonword repetition tasks tap into temporary

storage of phonological stimuli (in the phonological store) as well as long-term lexical

knowledge (in the articulatory loop).

Rationale and Objectives of the Present Research

The overarching objective of the present research was to determine whether a nonword

repetition task based on the morphology of a foreign, and unfamiliar, language structure would

provide a purer assessment of the phonological storage component of PSTM than an NWR task

based on the structure of a familiar second language. It was anticipated that the lexicality effect

would be reduced if one could not rely on prior phonotactic knowledge when repeating

nonwords.

To date, only two studies have suggested that participants perform better on NWR tasks

based on their native language structure (i.e., English or Greek) compared to non-native language

structures (i.e., French or English; Masoura & Gathercole, 1999; Thorn & Gathercole, 1999).

Further research is needed to replicate these findings with NWR tasks based on different

combinations of native and non-native language structures. Furthermore, little is known about

performance on NWR tasks based on a foreign, and typologically remote, language structure.

Therefore the main objective of the current research was to determine whether repetition

accuracy for a NWR task derived from Hebrew would be influenced by the degree of familiarity

with the Hebrew language. It was hypothesized that on a Hebrew-like NWR task, participants

with some exposure to Hebrew as a second language (L2) would perform better than participants

without any exposure to any Semitic language. Furthermore, researchers have speculated that

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performance on non-native language NWR tasks is decreased because the effect of wordlikeness

is minimized; however, this has never been explicitly demonstrated. Therefore a secondary

objective of the present research was to establish that a foreign language NWR task would be

perceived as less wordlike than a native language NWR.

Two studies were conducted that involved young second language and monolingual

children. Study 1 was designed to test the hypothesis that participants with some exposure to

Hebrew as a second language (L2) would perform better than participants without exposure to

any Semitic language on a Hebrew-like nonword repetition task. The second study was designed

to test the hypothesis that, to English speakers, the Hebrew-like NWR would be lower in

wordlikeness than an NWR task based on the English language.

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STUDY 1

The Effect of Hebrew Language Exposure on Hebrew-Like Nonword Repetition

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Method

Participants

The data analyzed for this paper were drawn from two larger multi-cohort longitudinal

projects that were conducted by our laboratory in the greater Toronto region. The overall sample

for the current study consisted of 81 Grade 1 students from various language backgrounds,

including English as first language (EL1), English as a second language (ESL), and Hebrew

Immersion (HI).

The EL1 (n=31; 16 female, 15 male) and ESL (n=29; 12 female, 17 male) participants

were drawn from a larger research project (Project A) that included ESL and EL1 participants

from 13 public elementary schools in low SES, ethnically diverse neighbourhoods. Information

gathered from school files and teacher interviews was used to confirm language status and home

language use. Only ESL students with Punjabi as a first language (L1) were selected; they were

matched with EL1 students primarily based on nonverbal ability and, when possible, on gender.

Punjabi and English are related because they have descended from the Centum and Satem

branches of the Indo-European language family, whereas Hebrew is more distant to Punjabi and

English because it is .!/01"2"3!4.567.60!89!2:0!;9<8.=".2"3!4.567.60!9.1"4>!?Woodard, 2004). The

data for the present study were collected in the winter of Grade 1 (age M=6.82, SD=.29).

The HI participants (n=21; 11 females, 10 males) were drawn from another larger

research project (Project B) that was conducted in a private English-Hebrew school, located in a

middle class neighbourhood. These participants were native English speakers who received

some Hebrew instruction. In Junior Kindergarten and Senior Kindergarten they were exposed to

Hebrew for about 2 hours per week, and in Grade 1 they received Hebrew instruction for about

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2.5 hours a day, five days per week. The data for the Hebrew participants were collected in the

spring of Grade 1 (age M=6.53, SD=.47)

Children included in the two projects were those: a) whose parents consented to their

participation, b) who had no known disability (e.g., sensory impairment, autism), c) who had

lived in an English-speaking country for at least 4 months. The purpose of the 4 month criterion

was to ensure that all ESL participants had sufficient command of English to understand test

instructions.

Materials

Hebrew-Like Nonword Repetition Task (HNWR). Hebrew is considered to be remote

from English in terms of morphology and syllable structure (Ravid & Schiff, 2009). Therefore, a

non-word repetition task based on the phonotactic rules and dominant stress patterns of the

Hebrew language was administered (Farnia & Geva, 2011; see Appendix A). The non-word

repetition task consists of 27 Hebrew-like nonwords which gradually increase in number of

syllables. Participants were presented with an audio recording of each non-word, one at a time,

and were asked to repeat the nonword as accurately as possible. Children’s responses were

recorded on a tape-recorder and later scored for accuracy. A score of 1 was granted for each

correctly repeated item. Raw scores were used in the analyses. Cronbach’s alpha was used to

estimate the nonword repetition task’s reliability. The scale’s reliability coefficients reached an

acceptable level (Cronbach’s ! =0.80).

Nonverbal ability. The Matrix Analogy Test (MAT; Naglieri, 1989) was used to

measure nonverbal ability. Participants were shown an incomplete matrix and asked to select a

pattern that would complete the illustration. This measure is considered to be appropriate for

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assessing the nonverbal ability of children from diverse cultural backgrounds because it is

relatively free of cultural reference. This measure was used to match ESL and EL1 participants

on nonverbal ability.

Procedure

Trained graduate students and research assistants administered test batteries to

participants individually and in a quiet setting. The examiner read the consent script aloud and

all participants gave verbal assent. All participants possessed sufficient language proficiency to

understand the instructions that were delivered in English.

Results

A one-way ANOVA was conducted to confirm that, after the matching procedure, the

three language groups (EL1, ESL, and HI) were in fact equivalent in terms of nonverbal ability.

The results revealed that nonverbal ability did not differ as a function of language group, F(31,

49) = .66, p > .05.

A one-way ANOVA was used to compare performance on the Hebrew-like Nonword

Repetition Task (HNWR) among the EL1, ESL, and HI groups. Performance on the HNWR

differed significantly as a function of language background, F (2,78) = 13.75, p < .001 (See

Figure 1). Planned contrasts revealed that the HI group significantly outperformed the EL1 and

ESL groups, t(78) = 4.71, p < .001; this is a substantive finding because it represents a large

effect size (r = .47) and accounts for approximately 25% of the variance in NWR performance

(Cohen, 1988, 1992). A second planned contrast revealed that the EL1 group significantly

outperformed the ESL group on the HNWR task t(78) = -2.38, p < .001, representing a medium

effect size (r = .26), and accounting for approximately 9% of the variance in NWR (Cohen,

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1988, 1992). Finally, Bonferroni post-hoc comparisons indicated that HNWR scores of the HI

group (M = 18.33, 95% CI [16.45, 20.22]) were also significantly higher than those of the EL1

group (M = 14.16, 95% CI [12.25,16.07 ]), p = .007.

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STUDY TWO

The Wordlikeness of Nonword Repetition Tasks

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Study 1 showed that even some exposure to Hebrew has a facilitative effect on the ability

to repeat nonwords. In Study 2, it was anticipated that the effect of wordlikeness would be

diminished in a foreign-language NWR compared to an NWR task based on the morphology of a

familiar language. To answer this question, we asked English-speaking undergraduate students to

judge the wordlikeness of a Hebrew-like NWR and two English-like NWR tasks.

Method

Participants

The sample consisted of 52 adults enrolled in an undergraduate psychology course.

There were 30 female and 22 male participants. Although all participants were English speakers,

31 students reported that English was their L1 and 21 students reported that English was their

L2. Four participants reported familiarity with a Semitic language such as Hebrew or Arabic.

Materials

Wordlikeness Questionnaire. Subjective estimates of wordlikeness were obtained for

items taken from the Hebrew NWR task and two English-like NWR tasks (Farnia & Geva, 2011;

Wade-Woolley, 1999; Wagner, Torgensen, & Rashotte, 1999). An audio recording was created

of an English female speaker reciting, one at a time, all of the nonword items from each test.

Items from the three tasks were randomly interspersed and gradually increased in number of

syllables. After participants heard each nonword item there was a beep followed by a 5 second

pause to provide the participant with sufficient time to make a rating of wordlikeness (see

Appendix A). Students were instructed to rate the extent to which the non-word sounds similar to

real words in the English language.!They were also advised to consider how likely it would be to

find these particular sounds in this position (beginning/ middle/ end) of an English word.

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Nonword repetition tasks. The two English-like NWR tasks are described in greater

detail below, and the Hebrew-like NWR is described in Study 1. All items from an adapted

version of Gathercole’s Students’ Test of Nonword Repetition were included in the

Wordlikeness Questionnaire (GNWR; see Appendix A; Wade-Woolley, 1999). This measure

was adapted from the original by Gathercole, Willlis, Baddeley, and Emslie (1994) in order to

avoid nonword items containing phonemes or syllable structures that were absent in the

participants’ L1. The adapted NWR task contained 25 nonwords gradually increasing in length

from one to five syllables. All items from the Comprehensive Test of Phonological Processing

(CTOPP) Nonword Repetition task (Wagner et al., 1999) were included in the Wordlikeness

Questionnaire. This 18-item subtest measures an individual's ability to repeat a series of

nonwords that range in length from 3 to 7 syllables.

A group of 52 undergraduate students listened to the audio recording and were asked to

rate the wordlikeness of each nonword, using a scale that ranged from 0 (“Not at all”) to 4 (“To a

great extent”). Mean ratings were calculated for each of the NWR tasks. The scales’ inter-rater

reliability coefficients reached an acceptable level (Cronbach’s !=.80).

Procedure

The primary investigator administered the Wordlikeness Questionnaire to participants in

a group format in their classroom. The examiner read the consent script aloud and all

participating students gave written consent. Participants were informed that their test results were

anonymous and that they had the right to discontinue the study at any time.

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Results

To minimize the effect of four outliers in the wordlikeness variable, a Winsorizing

technique as described by Tabachnick and Fidell (2007) was applied. The data were discarded

for two participants who did not fully complete the questionnaire. The four participants with

familiarity with a semitic language were kept in the analyses because their ratings of HNWR

wordlikeness were not significantly different from ratings of participants without familiarity with

a semitic language, t(50) = 1.49, p > .05. EL1 and ESL participants did not provide significantly

different ratings of wordlikeness; for the HNWR (M=.52, SE=.07, vs. M=.44, SE=.07), t(50) =

.78, p > .05; the CNWR (M = .94, SE = .08 vs. M = .85, SE = .07) t(50) = .86, p > .05; or the

GNWR (M = 1.69, SE = .11 vs. M = 1.71, SE = .11), t(50) = -.11, p > .05.

A one-way repeated measures ANOVA was conducted to compare the effect of

wordlikeness across three NWR measures (HNWR, CNWR, GNWR). The means and standard

deviations for mean wordlikeness ratings are presented in Figure 2. Mauchly’s test indicated that

the assumption of sphericity had been violated, !2 (2) = 19.27, p < .01, therefore degrees of

freedom were corrected using Greenhouse-Geisser estimates of sphericity (" = .76). The results

of the analysis revealed a significant effect of wordlikeness on nonword repetition tasks F(1.5,1

77.29) = 221.18, p < .001. The means and standard deviations for wordlikeness are displayed in

Figure 2.

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Follow-up repeated contrasts indicated a significant linear effect with wordlikeness

means increasing across measures F(1, 51) = 274.41, p < .001. Post hoc comparisons were

conducted with three paired samples t-tests using the Bonferroni correction. Firstly, mean

wordlikeness scores for the HNWR task (M = .49, SD = .35) were significantly lower than the

CNWR (M = .90, SD = .40) task t(51) = -8.76, p < .001. Secondly, mean wordlikeness scores for

the HNWR task (M = .49, SD = .35) were significantly lower than the GNWR task (M = 1.70,

SD = .58), t(51) = -16.57, p < .001.Thirdly, the mean wordlikeness scores for CNWR task (M =

.90, SD = .40) were significantly lower than the GNWR task (M = 1.70, SD = .58), t(51)= -15.40,

p < .001.

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Discussion

Summary of Findings

Study 1 examined whether non-word repetition tasks, designed to measure phonological

short-term memory, are influenced by familiarity with lexical representation of a given language.

The results demonstrated that approximately 25% of the variance in NWR scores could be

accounted for by long-term lexical knowledge. Overall, the present findings contribute further

evidence to the linguistic hypothesis, that NWR accuracy is closely related to one’s language

exposure. On the nonword repetition task that was based on Hebrew morphology, participants

who had some exposure to Hebrew as a second language performed better than participants

without any exposure to Hebrew or any other Semitic language. This demonstrates that we can

indeed bolster PSTM with prior phonological and morphological knowledge when repeating

nonwords based on a familiar second language. These findings are consistent with Masoura and

Gathercole’s (2005) study that found NWR performance to be better for tasks based on one’s

native language (Greek) compared to a foreign second language (English). Interestingly, in the

present study even two years of Hebrew exposure in a school context bolstered performance on a

Hebrew-like NWR task. Therefore, depending on the task, long-term lexical knowledge can be

accessed from one’s native language or from one’s second language in order to bolster NWR

performance. Presumably, the Hebrew immersion group was better able to maintain

representations in the phonological store using a redintegrative process that introduces long-term

knowledge of Hebrew phonological units. On the other hand, NWR scores were lower for

participants without Hebrew knowledge since they had to rely more heavily on their

phonological store to temporarily maintain novel phonological sequences. The weaker Hebrew-

like NWR performance of participants without Hebrew language exposure suggests that a NWR

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task based on a typologically remote language structure minimizes participants’ ability to employ

existing knowledge of phonological repertoires and phonotactic rules. The present study makes

a noteworthy contribution to the literature by suggesting that a NWR based on an unfamiliar

foreign language allows us to better isolate the capacity of the phonological store.

One unexpected finding was that the EL1 group outperformed the ESL group on the

Hebrew-like NWR. Since both EL1 and ESL groups were unfamiliar with Hebrew word

patterns, it was initially expected that they would perform similarly on the Hebrew-like NWR.

Since ESL and EL1 groups were matched on nonverbal ability and gender, group differences on

these factors can be ruled out as potential explanations. Another possible explanation that was

considered is whether Hebrew word patterns are more similar to English than to Punjabi (the L1

of the ESL participants). However, upon further investigation, there appears to be greater cross-

linguistic similarity between Punjabi and English because they share a common language family

(Indo-European) whereas English and Hebrew do not (Indo-European vs. Afroasiatic; Woodard,

2004). Also, Hebrew morphology is unique because of its use of the binyanim system (Berman

& Bolozky, 1978), therefore in terms of morphology, it seems that Hebrew is more distal to

English than Punjabi is. To fully appreciate this issue, further research is needed to compare the

phonology, morphology, and syntax of these languages.!Another potential explanation to

consider is that differences between ESL and EL1 participants on HNWR performance could be

due to group differences in socioeconomic status (SES). Although SES data were not collected,

one could assume that these groups are equivalent in terms of SES because they were drawn

from the same schools and neighbourhoods. Further research is warranted to explain why native

English speakers are more accurate than native Punjabi speakers at repeating HNWR.

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In the second study, the effect of wordlikeness was compared on NWR tasks derived

from a familiar and unfamiliar language structure. English speakers rated the Hebrew-like NWR

task to be significantly lower in wordlikeness than the English-like NWR tasks. Gathercole

(1995) has established that an NWR low in wordlikeness provides a more exact measure of

phonological storage capacity. The lower wordlikeness of the Hebrew-like NWR explains why it

was found to be a better predictor of vocabulary than an English-like NWR, when examined

concurrently and longitudinally (Farnia & Geva, 2011; Kornacki et al., 2011).

Furthermore, there were significant differences in wordlikeness detected between the two

English-like NWR tasks. The adapted Students’ Test of Nonword Repetition (Wade-Woolley,

1999) was significantly lower in wordlikeness than the Comprehensive Test of Phonological

Processing (CTOPP) Nonword Repetition measure. It is feasible that the greater wordlikeness of

the Students’ Test of Nonword Repetition could be an unintended consequence of the

adaptations made to avoid nonword items containing novel phonemes or syllables. The use of

the CTOPP NWR measure is widespread. These findings suggest that although the CTOPP

NWR provides a more sensitive assessment of the phonological storage capacity than other

English-like NWR tasks, a foreign NWR appears to further increase accuracy in the assessment

of the phonological store.

This dissertation bridges findings from two areas of research supporting the linguistic

hypothesis: the wordlikeness effect and increased performance on NWR tasks based on a

familiar language structure. In summary, an NWR task based on the phonological structure of a

foreign language was found to be lower in wordlikeness and repetition accuracy than a nonword

repetition task based on a familiar phonological structure. Taken together, these findings suggest

a solution to the ongoing debate in the literature about the lexicality effect in nonword repetition.

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Using an NWR task based on the morphology of a novel language structure minimizes the

lexicality effect, and thereby provides a more valid and robust measure of the phonological

storage system underpinning vocabulary acquisition. !

Limitations

A number of caveats need to be acknowledged regarding study 1. In order to compare

HNWR performance between participants with or without Hebrew exposure, I used archival data

from two separate research projects. As a result, there were differences between the ESL and

EL1 groups (from project A) and the HI group (from project B). The most important difference

between the participants across projects was socioeconomic status, since participants from

project A attended public school and participants from project B attended private school. It

should also be noted that there may be cohort effects, since the data for project B were collected

more recently than the data for project A. Therefore, it is feasible that the differences in HNWR

found between the ESL, EL1, and HI groups are in fact due to some normative history graded

influence (Feldman, 2006). Moreover, the number of participants from the Hebrew group was

somewhat smaller than the number of participants in the ESL or EL1 groups. This is because

there were fewer participants from project B than project A who completed the HNWR task in

Grade 1.

In Study 2, ratings of wordlikeness were measured using only subjective ratings. Thus,

further research is needed to determine whether objective ratings (i.e. number of grammatical

morphemes) are consistent in identifying foreign NWR items as being lower in wordlikeness

than an NWR based on a native or familiar language. Secondly, the sample contained a high

proportion of ESL and multilingual participants; although no significant differences were found

between ESL and EL1 wordlikeness ratings it is possible that L1 or L2 knowledge may have

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inadvertently impacted multilingual participants’ ratings of English wordlikeness. Further

research is necessary to confirm whether the current findings can be generalized to a

monolingual English sample.

Implications

Researchers and clinicians should consider administering NWR tasks based on a foreign,

and typologically remote, language structure. Firstly, NWR tasks based on a foreign language

provide a purer measure of the capacity of the phonological store, apart from long-term lexical

knowledge. Secondly, English-like nonword repetition tasks may give native English speakers a

slight advantage, and thereby somewhat underestimate the PSTM of recently immigrated ESL

students in comparison. Thus, by using an NWR task based on a language structure that is

unfamiliar to all participants, we can measure PSTM in a way that doesn’t give advantage to

English native speakers or proficient ESL speakers.

!

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References

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Appendix A

Materials

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Hebrew-like Nonword Repetition Task

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Adapted Version of Children’s Test of Nonword Repetition

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Wordlikeness Questionnaire

Instructions

• Ensure that you are free of distractions for 15 minutes. Please put away your laptop and

cellphone.

• Please listen to the accompanying audio file while you are completing the questionnaire.

• After you hear each word, a beep will sound to indicate that you will have 5 seconds to

respond.

• If you did not hear a word, place a dash next to it. After we hear the whole CD I will ask

whether anyone would like for me to repeat a word.

• For every item please rate the following: To what extent does this non-word sound

similar to real words in the English language? Please consider how likely it would be

to find these sounds in this particular position (beginning/ middle/ end) of an English

word.

• Provide your rating for each item by placing a check-mark (!) in the corresponding box

(0= Not at all, 1= Very little, 2=Somewhat, 3= Very Much, 4= To a great extent)

• After you have completed the questionnaire, please return your questionnaire and consent

form to the researcher.

• If you indicated that you are interested, you will receive by email an information letter

describing in more detail the purpose of this study.

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