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Schlagwörter:
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Zusammenfassung:
Infants and adults learn new phonological varieties better when exposed to multiple
speakers rather than a single speaker during learning (Bradlow & Bent, 2008; Rost & McMurray,
2009, 2010;Lively, Logan & Pisoni, 1993), presumably because such input is more varied. The
studies here test (1) whether having a larger social network similarly facilitates phonological
performance, and (2) what the underlying mechanism of this effect is.
In Study 1, 60 native Dutch speakers reported all their interactions for one typical week.
They were then tested on transcription of
nonwords
in noise, on talker normalization, and on a
host of cognitive measures (WM, auditory STM, selective attention, task switching). Results
showed that, as predicted, participants with larger social networks were significantly better at
speech perception in noise, but they were not better at talker normalization. Crucially, these
findings were obtained despite controlling for cognitive skills and for amount of talk, indicating
that the effect of social network size on speech perception is not due to differences in cognitive
skills among people with different network sizes or to amount of linguistic input.
Study 2 used computational simulations with agent-based models to explore the
mechanism underlying the effect of social network size on speech perception. Networks were
created by randomly selecting people from a population speaking 12 Dutch vowels with a mean
and SD as described in Pols, Tromp & Plomp (1973). During interactions, the agent met with a
random member of her network and received one labeled set of formants for each vowel, and
stored it. At test, the agent received unlabeled sets of formants from members of the population
that are not in her network, and needed to recognize them. Results showed that having a larger
social network led to greater accuracy in phoneme categorization. Interestingly, even though
larger networks were also associated with greater variability, as reflected in larger category
SDs, variability did not predict performance. Instead, as Figure 1 illustrates, the benefit of having
a larger network was fully explained by a novel measure of Smooth Sampling, which calculated
coverage of central areas and penalized for vowel overlap.
Further simulations that
manipulated network properties
orthogonally showed that the positive effect
of social network size on speech perception
is independent of amount of input received
but is modulated by the ratio of int
ra- to
inter-individual variability, such that having
larger social networks is most helpful when
speakers are consistent within themselves,
and the population is varied. These results
held whether phoneme categorization was
carried out by matching to the closest
similar stored token or by calculating the
token’s probability of belonging to each
category according to the category’s
distribution.
Together, these studies show how having a larger social network leads to better speech
perception by influencing the distribution of the input, and thus show how aspects of our life-
style can influence our linguistic performance
