[Paper Review - Psycholinguistics] Supporting Information (Bergelson & Aslin, 2017)

 Supporting Information

Bergelson & Aslin, 2017

• - 0;6 looked significantly more at named target images when the competitor images were semantically unrelated (e.g., milk and foot) than when they are related (e.g., milk and juice), just as older learners do. 
• - Home-lab links: common noun "copresence" correlated with in-lab comprehension. -> cross-word relations are formed early and the home learning environment measurably helps shape the lexicon from the outset. 
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1. 1. Introduction 

• It is relatively easy to examine infants' phonetic development 

1. • 0;6 infants have begun understanding nouns, suggesting they form word-referent links 
   • 0;6 sensitivity to vowels / 0;12 to consonants  

• Motivation: "While toddlers are sensitive to visual similarity, shape, and semantic category, little is known about nascent semantic representations." 
• Some literature 

1. • Arias-Trejo & Plunkett: visual similarity & category membership contribute to semantic competition 
   • Bergelson & Aslin: 1;0-1;8 infants' semantic specificity increases (e.g., 1;0 infants' labeling a cookie as either "cookie" or "banana" while the older ones do less)  
   • Adults consider semantic and perceptual relations among words in both the visual world paradigm and lexical decision tasks. 

• Research question: knowledge of how words are related goes hand in hand with knowledge of what words mean; is this true for infants' earliest words, or whether initial words are more like "islands," unrelated to other emerging lexical entries? 
• Method: gathering real-time processing data through in-lab eye tracking & home recordings 

1. • Question 1: Does semantic relatedness between visually available referents influence word comprehension in novice word learners? -> presented infants with image pairs that were either semantically related or unrelated (e.g., car-stroller or car-juice); one image was named aloud (e.g., car)
   • Question 2: Do readily measurable aspects of infants' home life account for those same infants' variability in word comprehension? -> gathered daylong audio and hour-long video recordings from infants in their homes and examined those time slices when concrete nouns were directed to the infant 
   • Referential transparency: infants learn nonnouns later than common nouns /. Referential transparency boosts learnability? 

• Hypothesis: if young infants are influenced by semantic relatedness, we predict better performance in the unrelated trials. 

2. Results

• Eye-tracking results 
• Measurement: where the child was looking for each 20-ms bin during the test trials (i.e., the target or distractor interest areas, or neither) 
• Two-time windows: a pretarget baseline from trial start to target word onset & a posttarget window from 367 ms to trial end 
• The standard baseline-corrected target looking metric: calculate target / (target+distractor) in the posttarget window and subtracts this same proportion from the baseline window  

• Two-tailed t-test: performance was significantly above chance on unrelated trials  

  -> Infants looked more at the labeled image on unrelated trials than on related trials. 

• Home-recording results

• Annotation: utterance type (syntactic & prosodic features into 7 categories), object copresence (yes, no, & unclear), & speaker 

  -> Although infants heard more object word input in the audio recordings in an absolute sense, they heard relatively more input in the videos.  

3. Discussion

• 0;6 infants understand words more readily when shown two semantically unrelated referents than when shown two related ones. 
• In-lab word comprehension is linked with referential transparency in the home, but not with measures of talker or utterance-type, and only marginally with input quantity. 
• [eye-tracking] even first words are not unconnected islands of meanings; they already contain semantic structure 
• Infants may know enough about a word's meaning to tell it apart from the unrelated referent but not the related one. 
• Object copresence significantly correlated with in-lab comprehension. 
• Referential transparency for a given infant may map onto that same child's comprehension, within the already referentially transparent noun class.