Study 4a: Introduction

In chapter 3, we investigated when and how children learn to link their abstract syntactic representations to the developing verb lexicon. We found that, although only adults showed evidence of a lexical boost, both children and adults were sensitive to the target verb (target verb bias) and the prime verb (prime surprisal). As such, we suggested that children acquire abstract knowledge of structure, and develop links between this knowedge and verbs early in acquisition. We also found that while target verb bias was larger in adults than in children, prime surprisal was larger in children than in adults. One explanation that we offered for this pattern of results was that verb- structure links are developed by means of an error-based learning

mechanism with a variable learning rate. In this type of mechanism, an initial high learning rate would cause large fluctuations in children’s early verb biases but smaller changes in adult verb biases. This can explain why we saw larger prime surprisal effects in children than we did in adults. Another possibility, however, is that the adults in our study were simply too familiar with the verbs in both the DOD and PD structure for them to be surprising in

either. For example, even though the verb give is DOD-biased, adults will,

presumably, have heard give more often than children in its dispreferred

structure (i.e., PD structure; Wendy gave a dog to Bob). Thus, adults’

familiarity with the prime and target verbs in our previous study (and not an error-based learning mechanism with a variable learning rate) could be responsible for our earlier findings. One way to test this would be to

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Chapter 4 investigate whether adults show larger prime surprisal effects with verbs that

are less familiar to them. The current study examined just this: using a structural priming paradigm, we examined the effect of verb bias on structural priming in adults with low-frequency verbs.

The idea that speakers are sensitive to the distributional information to which they are exposed is not an unfamiliar one. For example, research has shown that the frequency with which children hear verbs in their particular argument structures influences how they then use these verbs in

experimental tasks (Matthews, Lieven, Theakston, & Tomasello, 2005). Findings have also shown that adults are able to monitor the transitional probabilities between syllables and that these distributional cues are important for word segmentation (Saffran, Aslin, & Newport, 1996). In addition, frequency effects are well-documented across other linguistic domains including in sentence comprehension (e.g., Juliano & Tanenhaus, 1993), in the acquisition of inflectional endings (e.g., Dąbrowska, 2008), and in adults’ judgements of the grammaticality of overgeneralisation errors (e.g., Ambridge, Pine, Rowland, & Chang, 2012; Ambridge, Pine, Rowland, & Young, 2008; Stefanowitsch, 2008; Theakston, 2004; see Ambridge, Rowland, Theakston, & Kidd, in press, for a review of frequency effects in acquisition).

Further still, the frequency with which a verb appears in a particular syntactic structure has also been shown to influence structure choice in adults. As discussed in the previous chapter, behavioural evidence has revealed that structural priming is stronger when there is a mismatch

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Chapter 4 effect called prime surprisal (Bernolet & Hartsuiker, 2010; Jaeger & Snider,

2013). These prime surprisal effects have also been simulated in the Dual- path model - a frequency-based connectionist model that conceptualises syntactic processing and development in terms of error-driven learning (Chang, Dell, & Bock, 2006). Because the model tracks the frequency with which syntactic categories co-occur, it develops representations based on the semantic and structural properties of verbs and, as a result, is able to make frequency-based predictions about the upcoming words in a sentence. Thus, not only does the research indicate that adults are statistical learners, and that this has consequences for how they store and represent syntactic information, but it also suggests that they make use of highly predictive mechanisms for processing language. Given this, it is surprising that structural priming effects have rarely been interpreted in the light of lexical effects such as verb frequency and verb bias.

One recent study by Ivanova, Pickering, Branigan, McLean, and Costa (2012), however, has touched on the issue of verb frequency by priming adults with verbs that they have never heard before. In their task,

adults read dative primes containing novel verbs (e.g., The waitress brunks

the book to the monk) and dative primes containing known verbs (e.g., The waitress chucks the book to the monk), before describing target pictures with

known dative verbs (e.g., The prisoner gives the ball to the swimmer).

Ivanova et al. found that, despite the fact that these novel verbs had had no entries in the lexicon, adults were primed just as much by sentences with novel verbs as they were by sentences with known verbs. Not only do these results suggest that adults have similar syntactic representations for both

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Chapter 4 anomalous and well-formed sentences, but they also suggest that adults’

processing of anomalous sentences to produce well-formed sentences is not dependent on lexical information. Thus, the structural priming literature is beginning to gather evidence about how lexical effects like verb frequency impact on the way in which syntax is represented and processed. There is, however, room for further exploration – especially since little work has investigated whether both verb frequency and verb bias affect adults’ responses in structural priming tasks.

4.1.1. The current study

The current study, therefore, used structural priming to further investigate how adults’ lexical knowledge is linked to their knowledge about syntactic structure. To do this, we examined the impact of two lexical effects, verb frequency and verb bias, on adults’ responses in a structural priming task. In the previous chapter, we tested whether adults were sensitive to verb-

structure mismatches with verbs that are heard fairly often in the input. In this study, we tested whether adults also show sensitivity to verb-structure

mismatches, but instead with verbs that are less familiar to them.

As a pre-requisite of testing this aim, the study first assessed whether adults show evidence of abstract structural priming with low-frequency DOD- and PD-biased verbs (aim 1). That is, are adults more likely to produce DOD target responses after DOD primes, than after PD primes? It is well-reported that adults have abstract representations of the dative structure that enable them to generalise across sentences with high-frequency dative verbs (Bock,

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Chapter 4 1986; Rowland et al., 2012). Findings have also revealed that adults are

primed by sentences containing novel verbs just as much as they are by sentences containing known verbs (Ivanova et al., 2012). Given that adults have abstract representations that do not appear to rely on lexical

information, we should expect the adults in this study to show evidence of abstract structural priming with low-frequency verbs.

Second (aim 2), we examined whether adults show prime surprisal effects with low-frequency verbs, and also compared whether the size of these effects is larger than those reported in our previous study. Despite emerging evidence showing that adults are sensitive to verb-structure mismatches (Bernolet & Hartsuiker, 2010; Jaeger & Snider, 2013), our previous study revealed only a marginal prime surprisal effect in adults, a much smaller effect than in children. One possible explanation for the size of this effect is that the prime sentences in our task were not surprising

because the verbs used are ones heard too frequently in both DOD and PD structures by adults to be unexpected in either. A prime sentence containing a mismatch between a prime verb’s bias and its structure might be more unexpected with infrequent verbs. We might, therefore, expect prime surprisal effects to be larger with low-frequency verbs than with high- frequency verbs.

4.2. Study 4a: Method