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Abstract:
exical biases have been the focus of much recent research in
computational and psycholinguistics (see, e.g., papers in
MacDonald, 1997). We report on an experiment investigating the
effects of verb transitivity biases, i.e., the likelihood with
which a verb will be transitive rather than intransitive, on
aphasic sentence comprehension.
In a plausibility judgement task, subjects were asked to judge
the plausibility of (active and passive) transitive and
intransitive sentences (examples in Table 1 below). Sentences were
presented auditorily. Subjects indicated their response
("plausible" or "implausible") by pressing keys on a button box. We
tested 10 verbs with strong transitive bias, and 10 verbs with
strong intransitive bias. Verb biases were estimated based on
corpus counts in the British National Corpus. Three sentence types
were tested: active transitive, passive, and intransitive. Each
verb appeared twice in each condition, for a total of 240 stimuli.
In one condition, the sentence type (transitive or intransitive)
matched the lexical bias of the main verb. In a second condition,
the transitivity of the sentence was the opposite of the verb's
bias. We tested 3 chronic Wernicke's aphasics, 3 chronic Broca's
aphasics, and 3 age-matched nonaphasic controls. We recorded the
nature of the response ("correct" or "error") and the reaction
times. The main finding was that, in the analysis of reaction
times, each group showed an effect of conformity to verb bias for
passive sentences. In this condition, reaction times were
significantly longer for the sentences that did not conform to the
verb bias. This effect was strongest in the patients with
Wernicke's aphasia. Interestingly, this pattern was also found in
the error rates for the Wernicke's aphasics, but not for the
Broca's aphasics. For active transitive and intransitive sentences,
reaction times also tended to be longer in the "against bias"
conditions, although this effect did not reach statistical
significance in all groups and for all sentence types.
The findings suggest that miscomprehension of passive sentences
in aphasia, which has long been noted as a characteristic of
'agrammatic' comprehension (cf., e.g., Caplan et al., 1985; but see
Berndt et al., 1996 on the extent of between-subject variability on
this point), is not due to structural factors alone, but is
sensitive to lexical effects. We discuss implications of these
findings for accounts of lexical factors in aphasic sentence
comprehension.
References
Berndt, R. S., Mitchum, C. C., & Haendiges, A. N. (1996).
Comprehension of reversible sentences in 'agrammatism': A
meta-analysis.
Cognition,
58, 289-308.
MacDonald, M. (Ed.) (1997).
Language and Cognitive Processes,
12 (2/3), Special Issue on Lexical Representations and Sentence
Processing.
Caplan, D., Baker, C., & Dehaut, F. (1985). Syntactic
determinants of sentence comprehension in aphasia.
Cognition,
21, 117-175.
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