Appendix A: Descriptions of the predictors considered in this study
Japanese-English-bilingual-specific lexical predictors. Phonological similarity(PhonologicalSimilarityJPN) is a rated cross-language phonological similarity measureobtained by 10 Japanese speakers. Participants completed, in a spread sheet, phonologicalsimilarity between English words (1st column) and Japanese words (2nd column), using a
7-point scale. In order to safeguard PhonologicalSimilarityJPN from potential confoundarising from other lexical knowledge, we also considered objective Levenshtein distancecoding phonological similarity (PhonologicalDistance). PhonologicalDistance gauges
the number of operations required to transform Japanese words into the corresponding
English translation equivalents in their phonologically transcribed form (Levenshtein,1966; Yarkoni, Balota, & Yap, 2008; Dijkstra et al., 2010; Gooskens & Heeringa, 2004;
Schepens, Dijkstra, & Grootjen, 2011; Schepens, Dijkstra, Grootjen, & van Heuven,2013) based on the sdists function available in the R package cba (Buchta &Hahsler, 2009). In order to compare words of different lengths, we normalized thephonological Levenshtein distance based on the length of target English words (M = 4.3,SD = 1.4).
SemanticSimilarity was based on 10 Japanese-English bilingual readers’ ratings oncross-language conceptual similarity. English and Japanese words were presented to theraters side-by-side in two columns in a spreadsheet (English words in the 1st column andJapanese words in the 2nd column). Using a seven-point scale (1 = very different, 7 =identical), the raters assessed the extent to which katakana loanwords in Japanese weresimilar in meaning to the corresponding English target words and whether any Japanesekatakana words were completely unfamiliar to them.

FreqJPN reflected how many times Japanese katakana words appeared in aJapanese newspaper corpus containing over three million words and covering the 14-year
period from 1985 to 1998 (Amano & Kondo, 2003). FreqJPN was log-transformed, as its
distribution had a long right tail. Note that it is often also possible to translate English
words to logographic kanji or moraic kana words, as well as katakana loanwords.
However, because the log-transformed frequency of kanji or kana translations obtained
from the same corpus was not a significant predictor, we do not further discuss it.
Although FreqJPN comprises two distributions due to zero frequency ofoccurrence for some words, the corresponding log-transformed Google document
frequency measure (GoogleFreqJPN) does not indicate such qualitative difference among
the set of katakana words (see Appendix B). This suggests that the zero frequencies in
FreqJPN are not due to qualitative differences with respect to words’ lexical status, suchas transliterations and translations, but due to the fact that the written word corpus isconservative for the purpose of the present study (i.e., it provides frequency counts forkatakana words only up to the year 1998 and only in the context of newspaper texts).
Finally, a factor Cognate (levels: Cognate and NotCognate) was considered inaddition to the above mentioned numerical predictors. Because considerable semantic
and phonological overlap and sufficient exposure to words are expected for such special
cognate representations to emerge in the first place, words with larger-than-the-averagevalues in all FreqJPN, PhonologicalSimilarityJPN, and the conceptual similarity werecategorized into Cognate (N = 58).
Lexical distributional predictors of the target English words. As orthographicpredictors, we considered word length (Length) and orthographic Levenshtein distance(OLD20, Yarkoni et al., 2008). A low OLD20 score indicates that a given word is locatedwithin a dense orthographic space. To measure English word frequency, we used logtransformed FreqHAL (HAL: Hyperspace Analogue to Language, Lund & Burgess,1996; Burgess, & Livesay, 1998, as available in Balota et al., 2007). SUBTLCD is a logtransformed context diversity measure based on a number of films in which a given word
had been used (Adelman, Brown, & Quesada, 2006; Brysbaert & New, 2009a, 2009b).
We also considered ratings of word Imageability. Because SemanticSimilarity is expected
to vary with imageability, with a larger cross-linguistic variance for abstract concepts
relative to concrete concepts, Imageability safeguards our rated SemanticSimilarity
measure. We obtained Imageability scores rated by 10 native English readers, using aseven-point scale (1 = not imageable, 7 = very imageable).
Task-related predictors and individual differences. In the response time
analyses, we considered the following variables: PreviousRT, inversely transformed RT
in the previous trial; Trial, the number of preceding trials; and PreviousResponseCorrect,
whether the responses in the preceding two trials were correct (see Baayen & Millin,2010 for autocorrelation in the time-series of response times). In the eye-movement
analyses, we also considered PreviousFixationDuration for second fixation duration
analyses to account for potential spillover effects from the previous fixation. PreviousRT
Trial, and PreviousResponseCorrect were also considered in the eye-movement analyses.
Consideration of readers’ L2 proficiency is also important because such individual
differences potentially lead to distinct processing mechanisms (Kroll & Stewart, 1994;
Potter, So, von Eckhardt, & Feldman, 1984). In our sample, we considered logtransformed participants’ months of stay away from Japan for each participant

(LengthOfStayCanada) in our regression analyses as a measure of L2 English
proficiency. LengthOfStayCanada naturally brings in several other components oflanguage proficiency; it highly correlated with age (r = 0.68, p = 0.001), with their
vocabulary size in English measured by X_Lex The Swansea Levels Test (Meara, 2005, r= 0.48, p = 0.03). We leave the specific advantages and disadvantages of other related
measures to future research.

Appendix B: A matrix of scatterplots for Japanese and English frequencies.

Appendix C: A residualization procedure
In order to study independent contributions of lexical distributional properties, we opted
for a residulization procedure to resolve multicollineariies. For example, OLD20 highly
correlates with Length, SUBTLCD, and the number of meanings in WordNet (Miller,1990). OLD20 was therefore regressed on these three variables, and the residuals wereused as a new predictor OLD20_resid. The new predictor correlated significantly andstrongly with the original predictor (r = 0.67, p < 0.01 with OLD20). To safeguard ourmeasures, the same residualization procedure was applied to the following variables withhighly significant inter-correlations: SUBTLCD (regressed on FreqHAL and a number ofmeanings); Imageability (regressed on FreqHAL, Length, number of meanings); FreqJPN(regressed on FreqHAL, SUBTLCD, and number of meanings); SemanticSimilarity(regressed on FreqJPN and GoogleFreqJPN). After the residualization procedure, all thenew predictors correlated significantly with the respective original predictors: r = 0.67 for
OLD20_resid and OLD20, r = 0.75 for SUBTLCD_resid and SUBTLCD, and r = 0.95 for
FreqJPN_resid and FreqJPN. GoogleFreqJPN and PhonologicalDistance were notincluded in statistical models together with FreqJPN and PhonologicalSimilarityJPN but
considered separately to assess whether the pattern of results remains unchanged when
one predictor is replaced with another. Task-related variables PreviousRT andFirstSubgazeDuration were similarly regressed on correlated predictors (Trial for theformer and Trial, PreviousRT, FreqHAL, Length, and SUBTLCD for the latter), resulting
in PreviousRT_resid and FirstSubgazeDuration_resid.

Appendix D: Materials used in this study
English words used in the present study and their Japanese katakana translation andphonology. The flap /ɽ/ was used to encode English approximants /r/ and /l/. /ɸ/represents a voiceless bilabial fricative. Vowels and consonants were repeated in theJapanese phonological transcriptions to encode the Japanese-specific moraic long vowels,moraic nasals, and moraic obstruents. Words marked with * were excluded from theanalyses.
Englishword

Japanesekatakana

Japanesephonology

Englishword

Japanesekatakana

Japanesephonology

accentaccount
advanceadvantageadviceagendaamateur*anchoranswerappealarcade*architect
aspectattempt
auctionautumnavenueballoonballot*basketblanketbottombracketbreastbreathbronzebuffalobuffer

アクセント
アカウント
アドバンス
アドバンテージ
アドバイス
アジェンダ
アマチュア
アンカー
アンサー
アピール
アーケード
アーキテクト
アスペクト
アテンプト
オークション
オータム
アベニュー
バルーン
バロット
バスケット
ブランケットボトム
ブラケットブレスト
ブレス
ブロンズ
バッファローバッファー

akusennto
akaunnto
adobannsu
adobannteedʒiadobaisu
adʒenndaamatʃuaannkaaannsaaapiiɽuaakeedoaakitekuto
asupekuto
atemmputoookuʃonn
ootamuabenjuubaɽuunnbaɽottobasukettobuɽannketto
botomubuɽakettobuɽesutobuɽesubuɽonnzubaɸɸaɽoobaɸɸaalessonletterlibrary
licensemagazine
manifestmannermarblemarginmassagematrixmeasuremedicinemerchant
messagemethodministermiraclemirrormissionmomentmonstermorningmotionmountainmusclemuseumnatureレッスン
レター
ライブラリーライセンスマガジン
マニフェスト
マナー
マーブル
マージン
マッサージ
マトリックスメジャー
メディスン
マーチャント
メッセージ
メソッド
ミニスター
ミラクル
ミラー
ミッション
モーメント
モンスター
モーニング
モーション
マウンテン
マッスル
ミュージアムネーチャー

ɽessunnɽetaaɽaibuɽaɽii
ɽaisennsu
magadʒinnmaniɸesuto
manaamaabuɽumaadʒinnmassaadʒimatoɽikkusu
medʒaamedisunnmaatʃannto
messeedʒimesoddominisutaamiɽakuɽumiɽaamiʃʃonnmoomennto
monnsutaa
mooniŋŋgu
mooʃonnmaunntenn
massuɽumjuudʒiamu
neetʃaabulletbulletinbundleburdenbusinessbuttercabinetcameracandlecannoncareercartooncastlecatalogcathedral*
cattleceiling*
century
challenge
championchancechannelchaptercharacterchartercherrychocolatechurchcircuit*circusclustercollegecomment
complaint
component
condition
conflictcontent
cornercouplecoursecourtesy*
credit

ブレット
ブリテン
バンドル
バードン
ビジネス
バター
キャビネット
カメラ
キャンドル
キャノン
キャリア
カートゥーン
キャッスル
カタログ
キャシードラル
キャトル
シーリング
センチュリーチャレンジ
チャンピオン
チャンス
チャンネル
チャプター
キャラクターチャーター
チェリー
チョコレート
チャーチ
サーキット
サーカス
クラスター
カレッジ
コメント
コンプレイントコンポーネント
コンディション
コンフリクト
コンテント
コーナー
カップル
コース
カーテシー
クレジット

buɽettobuɽitennbanndoɽubaadonnbidʒinesu
bataa
kjabinettokameɽakjanndoɽukjanonnkjaɽiakaatuunnkjassuɽukataɽogu
kjaʃiidoɽaɽukjatoɽuʃiiɽiŋŋgusenntʃuɽiitʃaɽenndʒitʃammpionntʃannsutʃannneɽutʃaputaakjaɽakutaatʃaataatʃeɽiitʃokoɽeetotʃaatʃisaakitto
saakasukuɽasutaakaɽeddʒikomennto
kommpuɽeinnto
kommpoonennto
konndiʃonnkonnɸuɽikuto
konntennto
koonaakappuɽukoosu
kaateʃii
kuɽedʒittoneedlenoticenotionnumberoccasion
officeopinionopponent
optionpalaceparadeparadiseparadoxpencilpeninsula*
periodpersonnel
phantomplanetplastic
pocketpoisonpolicepolitics
povertypriestprinceprinciple
prisonprivilege
profileprogrampromiseprotestrabbitreceipt
reciperescueresultrocketsalarysamplesatellite*

ニードル
ノーティス
ノーション
ナンバー
オケーションオフィス
オピニオン
オポーネント
オプション
パレス
パレード
パラダイス
パラドックス
ペンシル
ペニンスラ
ピリオド
パーソネル
ファントム
プラネット
プラスチック
ポケット
ポイズン
ポリス
ポリティクスパーバティープリースト
プリンス
プリンシプル
プリズン
ブリビレッジプロフィール
プログラム
プロミス
プロテスト
ラビット
レシート
レシピ
レスキュー
リザルト
ロケット
サラリー
サンプル
サテライト

niidoɽunootisunooʃonn
nammbaaokeeʃonnoɸisu
opinionn
opoonennto
opuʃonnpaɽesupaɽeedopaɽadaisu
paɽadokkusu
pennʃiɽu
peninnsuɽapiɽiodo
paasoneɽuɸanntomu
puɽanettopuɽasutʃikku
pokettopoizunnpoɽisupoɽitikkusu
paabatiipuɽiisuto
puɽinnsu
puɽinnʃipuɽupuɽizunnpuɽibiɽeddʒipuɽoɸiiɽupuɽoguɽamu
puɽomisupuɽotesutoɽabittoɽeʃiitoɽeʃipiɽesukjuuɽizaɽutoɽokettosaɽaɽii
sammpuɽusateɽaito

crystalculturedamagedangerdebatedefensedegreedesigndiagramdiamonddilemma*disasterdiseasedistrict
doctrine*domaindonkeydragondungeon*effortelephant
embassy
emergency
emperor*episodeexampleexpertfashionfatigue*fellowfinanceflavorflightfriendgarbagegarlic*gendergrease*guitarhazardhelmetheroin*horizon

クリスタル
カルチャー
ダメージ
デンジャー
ディベート
ディフェンスディグリー
デザイン
ダイアグラムダイアモンドジレンマ
ディザスターディジーズ
ディストリクト
ドクトリン
ドメイン
ドンキー
ドラゴン
ダンジョン
エフォート
エレファントエンバシー
イマージェンシー
エンペラー
エピソード
エグザンプル
エキスパートファッションファティーグフェロー
ファイナンス
フレーバー
フライト
フレンド
ガービッジ
ガーリック
ジェンダー
グリース
ギター
ハザード
ヘルメット
ヘロイン
ホライズン

kuɽisutaɽukaɽutʃaadameedʒidenndʒaadibeetodiɸennsu
diguɽii
dezainndaiaguɽamu
daiamonndodʒiɽennma
dizasutaa
didʒiizu
disutoɽikuto
dokutoɽinndomeinndoŋŋkii
doɽagonn
danndʒonneɸootoeɽeɸannto
emmbaʃii
imadʒennʃii
emmpeɽaa
episoodo
eguzammpuɽuekisupaato
ɸaʃʃonnɸatiiguɸeɽooɸainansu
ɸuɽeebaa
ɸuɽaitoɸuɽenndo
gaabiddʒi
gaaɽikkudʒenndaaguɽiisugitaahazaadoheɽumettoheɽoinnhoɽaizunn

scheme*schoolsearchsecretarysentence
sessionshadowshield*soccersocketsoldiersourcespeechsponsorsquarestancestatue*statusstreetstrengthstringstudiosummersurface
syndrome
systemtalenttargettechniquetemplate
templeterritorytexture
theatrethreadthreshold*toilettraffic
tragedytreatytunneltwilight
vanilla

スキーム
スクール
サーチ
セクレタリー
センテンス
セッション
シャドー
シールド
サッカー
ソケット
ソルジャー
ソース
スピーチ
スポンサー
スクエア
スタンス
スタチュー
ステータス
ストリート
ストレングス
ストリング
スタジオ
サマー
サーフェス
シンドローム
システム
タレント
ターゲット
テクニック
テンプレート
テンプル
テリトリー
テクスチャ
シアター
スレッド
スレッシュホールド
トイレット
トラフィックトラジェディー
トリーティートンネル
トワイライトバニラ

sukiimusukuuɽusaatʃisekuɽetaɽii
senntennsu
seʃʃonnʃadoo
ʃiiɽudosakkaasokettosoɽudʒaasoosu
supiitʃisuponnsaa
sukueasutannsu
sutatʃuu
suteetasusutoɽiito
sutoɽenngusu
sutoɽiŋŋgu
sutadʒiosamaasaaɸesu
ʃinndoɽoomu
ʃisutemutaɽennto
taagetto
tekunikku
temmpuɽeetotemmpuɽuteɽitoɽii
tekusutʃaʃiataasuɽeddosuɽeʃʃuhooɽudotoiɽetto
toɽaɸikku
toɽadʒedii
toɽiitii
tonnneɽu
towaiɽaitobaniɽahusband
impactincentive
industry
insectinstinctinterest
intervalinterview
jacketleisure

ハズバンド
インパクト
インセンティブ
インダストリーインセクト
インスティンクト
インタレストインターバルインタビュー
ジャケット
レジャー

hazubanndo
immpakuto
innsenntibu
inndasutoɽii
innsekuto
innsutinnkuto
inntaɽesuto
inntaabaɽuinntabjuu
dʒaketto
ɽedʒaavehicle
ventureversion
veteran*villageviolinvitaminvolumeweatherwhistlewitness

ビークルベンチャー
バージョン
ベテラン
ビレッジ
バイオリン
ビタミン
ボリューム
ウェザー
ホイッスル
ウィットネスbiikuɽubenntʃaabaadʒonnbeteɽannbiɽeddʒibaioɽinn
bitaminnboɽjuumu
wezaa
hoissuɽu
wittonesuAppendix E: A direct comparison between monolinguals and bilinguals

Estimate, standard error, t-value, p-value, and effect size (ms) of the fixed effects in themodel of Japanese-English bilinguals and English monolingual readers’ lexical decision
response times analyzed together for a direct comparison of the two groups.

Response timeType(Intercept)
PreviousResponseCorrect (Error)
Trial
PreviousRTFirstLanguage (Japanese)
LengthFreqHALSUBTLCD_resid
Imageability_resid
FreqJPN_resid
PhonologicalSimilarity
SemanticSimilarity_resid
Length* FirstLanguage (Japanese)
Imageability_resid* FirstLanguage (Japanese)
Freq_HAL* FirstLanguage (Japanese)
FreqJPN_resid* FirstLanguage (Japanese)
FreqHAL* FreqJPN_resid
FreqHAL* FreqJPN_resid* FirstLanguage (Japanese)
PhonologicalSimilarity* FirstLanguage (Japanese)
SemanticSimilarity_resid* FirstLanguage (Japanese)

Task
Task
Task
IndividualEngl
EnglEnglEngl
Jpn-Engl
Jpn-Engl
Jpn-Engl
Engl* Individual
Engl* Individual
Engl* Individual
Jpn-Engl* IndividualEngl* Jpn-EnglEngl* Jpn-Engl* Individual
Jpn-Engl* Individual
Jpn-Engl* Individual

Estimate Std.Error t-value

p-value-1.9100.065-0.054
0.158
0.456
0.030
-0.031-0.059-0.009-0.004-0.001-0.014

0.044
0.009
0.006
0.014
0.054
0.008
0.007
0.008
0.004
0.003
0.006
0.011

-43.72
7.23
-8.79
11.67
8.39
3.90
-4.45
-6.99
-1.94
-1.77
-0.22-1.31< 0.0001< 0.0001< 0.0001< 0.0001< 0.0001
0.0001< 0.0001< 0.0001
0.05200.07630.82820.1901

0.019

0.007

2.69

0.0071

0.013

0.004

3.49

0.0005-0.036

0.007

-5.01

< 0.0001

0.001

0.002

0.64

0.5223-0.002

0.002

-0.70

0.4828

0.007

0.002

3.38

0.0007-0.013

0.005

-2.56

0.0105-0.024

0.009

-2.70

0.0070Effect size

17-63
115
127
24-41-66-14-13-2-1666 (Jpn)
24 (Engl)
15 (Jpn)-14 (Engl)-134 (Jpn)-41 (Engl)-17 (Jpn)-14 (Engl)
Appendix C(a, b)Appendix C(a, b)
Appendix C(c)Appendix C(d)Appendix F: Re-consideration of rated measures
As in many past studies, the present study relied on human rated measures.
However, there are many different ways to obtain rated measures, and there is noconsensus as to what best simulates on-line processing. The figure below summarizes thecross-language similarity measures in phonology and semantics (indicated by solid anddotted lines respectively).
In this study, the objective edit distance measure (PhonologicalDistance) replicatedthe late effect, but not early effects, of the rated PhonologicalSimilarityJPN successfully.
This may be due to Japanese-English late bilinguals’ incomplete mental phonologicalrepresentations of English words, which was not assumed for PhonologicalDistance.
When a rated phonological similarity based on an assessment by 10 native English
speakers was considered (PhonologicalSimilarityENGL, M = 4.3, SD = 1.1), this variablebehaved much like the objective PhonologicalDistance albeit the fact that
PhonologicalSimilarityENGL correlated with PhonologicalSimilarityJPN (r = 0.63, p <0.01) more strongly than PhonologicalDistance (r = 0.4, p < 0.01). In the
PhonologicalSimilarityENGL rating task, the English speakers saw English words on acomputer display, while they heard corresponding Japanese words recorded by a native
female Japanese reader.
Similarly, there are different ways to rate cross-language SemanticSimilarity. A
reviewer pointed out that the result might be different if semantic similarity is rated in thereversed direction (i.e., Japanese words in the first column and English words in thesecond column). We therefore collected ratings from 9 Japanese-English bilinguals(SemanticSimilarityReversed). This new measure correlates with SemanticSimilarity

largely (r = 0.73, p < 0.01) and replicated the semantic similarity effects (with aninteraction with PreviousRT) in response time and last fixation duration analyses.