The (in)dependence of articulation and lexical planning during isolated word production

ABSTRACT

The number of phonological neighbours to a word (PND) can affect its lexical planning and pronunciation. Similar parallel effects on planning and articulation have been observed for other lexical variables, such as a word's contextual predictability. Such parallelism is frequently taken to indicate that effects on articulation are mediated by effects on the time course of lexical planning. We test this mediation assumption for PND and find it unsupported. In a picture naming experiment, we measure speech onset latencies (planning), word durations, and vowel dispersion (articulation). We find that PND predicts both latencies and durations. Further, latencies predict durations. However, the effects of PND and latency on duration are independent: parallel effects do not imply mediation. We discuss the consequences for accounts of lexical planning, articulation, and the link between them. In particular, our results suggest that ease of planning does not explain effects of PND on articulation.

KEYWORDS:

• Language production
• lexical planning
• articulation
• neighbourhood density
• confusability

Acknowledgements

We are grateful for help from the following people: Kyle Gorman, Jonathan Howell, and Michael Wagner for providing us with their forced aligner; Andrew Watts, Peter Kremer, and audiences at the 2013 CUNY Sentence Processing Conference and the 2012 International Workshop on Language Production for feedback on earlier presentations of these results. We would also like to thank Susanne Gahl, Cassandra Jacobs, Sebastian Sauppe, Michael Vitevitch, and Andrew Wedel for comments on earlier drafts of this manuscript. Lastly, we would like to thank Jasmin Sadat and an anonymous reviewer for initial reviews of earlier drafts of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Esteban Buz http://orcid.org/0000-0002-0412-0320

T. Florian Jaeger http://orcid.org/0000-0002-1158-7308

Notes

1. Studies differ in how they calculate PND. Some calculate PND as the number of phonological neighbours that differ in only one segment from the target. Others sum the frequency of all neighbours (frequency-weighted PND, cf. Luce & Pisoni, 1998). Studies further differ in how edit distance is calculated (e.g. which operations of substitution, insertion, and deletion are considered) and in whether words that are morphologically related to the target are excluded when counting neighbours. We group these studies together and simply refer to their findings as PND effects.

2. The probability of a disfluency would be another measure of production difficulty (Shriberg, 1996). However, disfluent naming trials were rare in our experiment (5% of all trials). This left only 58 cases with disfluencies (out of 1139, prior to exclusions).

3. It is worth noting that recent work suggests that competition from additional neighbours only results in a net facilitation of lexical planning if the neighbours are only weakly activated (Chen & Mirman, 2012). Strongly activated neighbours, however, can result in inhibition of lexical planning. To the best of our knowledge, the predicted effect of weakly versus strongly activated neighbours on articulation has yet to be tested (though Baese-Berk & Goldrick, 2009; Kang & Guion, 2008; Kirov & Wilson, 2012; Seyfarth, Buz, & Jaeger, 2015, might be taken as initial evidence in support of this prediction).

4. Enhanced pronunciations of high PND words compared to low PND words were also found in a number of other studies (Scarborough, 2010, 2012, 2013; Scarborough & Zellou, 2013; Wright, 2004). However, these studies were targeted at a different research question, for which they confounded PND and word frequency. Since word frequency has been shown to affect vowel duration and dispersion (Munson, 2007), we do not consider these studies further (see also a recent reanalysis of Wright, 2004 by Gahl, 2015).

5. One source for differences between the studies could be differences in the amount of onset vs. rhyme neighbours (see below). Other differences include the much faster speech rates in conversational speech (see Gahl et al., 2012) and the presence of context in conversational speech, which might modulate which phonological neighbours affect articulation (for related discussion, see Heller & Goldrick, 2014).

Additional information

Funding

This work was supported by an NSF CAREER award [IIS-1150028] as well as an Alfred P. Sloan Research Fellowship to T. F. J. and an NRSA pre-doc [F31HD083020] to E. B. The views expressed here are those of the authors and do not necessarily express the official views of these funding agencies.