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Abstract:
Speech errors, while disordered speech, are
nonetheless remarkable in their orderliness; an example of this
is the lexical bias effect. Baars, Motley and MacKay
(1975), replicated by Dell (1986), found experimentally elicited
phoneme exchange errors ("barn door" spoken as "darn bore") are
more likely when the errors form words than when they form
nonwords ("dart board" spoken as "bart doard"). This effect
is initially puzzling. Generally, errors respect only the
constraints that apply to the processing level at which they
occur, e.g., phonological errors respect phonotactic, but not
syntactic category constraints.
Lexical bias could arise from feedback along
backward links from phonological to morpheme nodes in the
production system (Dell 1986; Dell & Reich, 1981).
Activated phonemes feed back to connected morphemes, which then
feed forward to other phonemes. This resonance of
activation makes word errors more likely, as nonwords have no
morpheme node to support the accumulation of activation.
However, these backward links are prohibited by the model of
Levelt et al. (1999). They instead account for the effect
via an editor, which is more likely to prevent nonwords from
being articulated than words.
This experiment investigates further the lexical
bias effect. We elicited phoneme exchanges from 100
speakers using stimuli where the error outcomes had either the
first word a real word, and the second a nonword, or vice versa
("dean beak" slips to "bean deak", word-nonword; "deal bead"
slips to "beal deed", nonword-word). This follows up Dell
and Reich's (1981) corpus finding that only the first words in
exchanges had a lexical bias.
We found that complete phoneme exchanges were far
more likely for word-nonword than nonword-word outcomes (47 vs.
19). This asymmetry can be accounted for naturally by a
feedback account, plus an incremental model of exchange errors
where they are precipitated by an anticipation (e.g., "dean beak"
starts as "bean ") displacing the intended phoneme ("d"), leaving
it nowhere to go but the vacated onset of the second word, thus
completing the exchange ("deak"). Feedback explains the
automatic lexical bias on the first word, and then the second
part of the error happens by default. The lexical editor
however, does not predict that word-nonword errors are more
likely than nonword-word errors, unless it specially adds a
mechanism by which the articulation of an initial nonword is more
likely to be prevented. Implications for feedback and
incrementality in models of language production will be
discussed.
References
Baars, B. J., Motley, M. T., & MacKay, D. G.
(1975). Output editing for lexical status in artificially
elicited slips of the tongue. Journal of Verbal Learning
and Verbal Behavior, 14, 382-391.
Dell, G. S., & Reich, P. A. (1981).
Stages in sentence production: An analysis of speech error
data. Journal of Verbal Learning & Verbal Behavior, 20,
611-629.
Dell, G. S. (1986). A spreading-activation
theory of retrieval in sentence production. Psychological
Review, 93, 283-321.
Levelt, W. J. M. (1989). Speaking: From
Intention to Articulation. Cambridge, MA: MIT Press.
Levelt, W. J. M., Roelofs, A., & Meyer, A. S.
(1999). A theory of lexical access in speech
production. Behavioral & Brain Sciences, 22,
1-75.
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