Phonological neighbourhoods in the developing lexicon

Abstract

Structural analyses of developing lexicons have provided evidence for both children's holistic lexical representations and sensitivity to phonetic segments. In the present investigation, neighbourhood analyses of two children's (age 3;6) expressive lexicons, maternal input, and an adult lexicon were conducted. In addition to raw counts and frequency-weighted counts, neighbourhood size was calculated as the proportion of the lexicon to which each target word is similar, to normalize for vocabulary size differences. These analyses revealed that children's lexicons contain more similar sounding words than previous analyses indicated. Further, neighbourhoods appear denser earlier in development relative to vocabulary size, presumably because children first learn words with more frequent sounds and sound combinations. Neighbourhood density as a proportion of the size of the lexicon then decreases over development as children acquire words with less frequent sounds and sound combinations. These findings suggest that positing fundamentally different lexical representations for children may be premature.

Fig. 1

Proportion of three-phoneme words in Adam’s (top panel) and Sarah’s (bottom panel) expressive lexicons and maternal input as a function of the number of phonological neighbours. Adult results are overlaid.

Fig. 2

Proportion of four-phoneme words in Adam’s (top panel) and Sarah’s (bottom panel) expressive lexicons and maternal input as a function of the number of phonological neighbours. Adult results are overlaid.

Fig. 3

Proportion of five-phoneme words in Adam’s (top panel) and Sarah’s (bottom panel) expressive lexicons and maternal input as a function of the number of phonological neighbours. Adult results are overlaid.

Fig. 4

Proportion of all words in Adam’s (top panel) and Sarah’s (bottom panel) expressive lexicons and maternal input as a function of the number of phonological neighbours. Adult results are overlaid.

Fig. 5

Frequency-weighted neighbourhood density for all words in Adam’s (top panel) and Sarah’s (bottom panel) expressive lexicons and maternal input. Adult results are overlaid.

Fig. 6

Mean number of neighbours as a function of word length in phonemes for both Adam’s and Sarah’s expressive lexicons, maternal input, and the adult lexicon.

Fig. 7

The number of words and the number of neighbours in the children’s lexicons as a proportion of the number of words and the number of neighbours in the adult lexicon, for words of different lengths.

Fig. 8

Proportion of all words in Adam’s expressive lexicon (top panel) and maternal input (bottom panel) and those same words in the adult lexicon as a function of the ratio of phonological neighbours to all monosyllabic words.

Fig. 9

Proportion of all words in Sarah’s expressive lexicon (top panel) and maternal input (bottom panel) and those same words in the adult lexicon as a function of the ratio of phonological neighbours to all monosyllabic words.