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Abstract:
English-speaking normal and language impaired
(SLI) children and agrammatic aphasics misunderstand passives
(1a) more often than actives (1b). In addition, normal adults
read passives more slowly than actives, although they rarely
misunderstand passives. When people misunderstand passives,
they typically interpret passives as if they were active.
Design. Although much psycholinguistic work
has investigated English passives, this is the first on-line
study of processing of spoken passives. Subjects listened
to 12 passive sentences (1a) and 12 active sentences (1b) and
chose which of two pictures corresponded to each sentence. Pairs
of pictures differed only in who was the agent.
(1a) The girl was pushed by the boy.
(1b) The girl was pushing the boy
The verbs
kiss
,
push
,
shove
,
sniff
,
tickle
and
touch
were used because they are easily depictable, and have an -
ed
passive participle. In half of the trials, the nouns were
a boy and a girl, and in half they were a man and a woman.
Each subject heard each verb twice in actives and twice in
passives, once with adult NPs and once with child NPs.
Whether the left or right picture was the target picture, whether
the agent was to the left or the right of the patient, and
whether a male or female character was the agent was balanced
within subjects.
Preschool children. Eight 3-year olds (mean
3;4) and 9 4-year olds (4;3) participated. Children were
faster (5289 msec vs. 5739 msec, p < .01, all RTs for correct
responses) and more accurate on actives than on passives (74% vs.
58%, p < .05). Three-year olds tended to do worse than
4-year olds (61% vs. 71%, p = .10), and there was an age x
sentence interaction (p < .005): 3-year olds were 160 msec
faster on passives, whereas 4-year olds were 1062 msec faster on
actives.
Eye-tracked children. 16 school-age children
(mean 5;8) participated. They were faster (4043 msec vs.
4643 msec, p < .005) and more accurate (94% vs. 78%, p <
.01) on actives than passives. Analyses of eye-movement
data collected using a mobile eye-tracker revealed that, for
active sentences, from the onset of the sentence until the onset
of the final noun, children consistently looked at the correct
picture approximately 55% of the time. Looks to the target
picture then increased linearly at a rate of 30 looks/sec until
they reached approximately 75% correct looks 300 msec after the
sentence was finished. Factoring in the amount of time it
takes to program an eyemovement, this suggests that children
'decide' an active sentence is active when they learn it contains
a progressive participle (or perhaps lacks a
by
phrase). For passive sentences, from the onset of the
sentence until the end of the sentence, children consistently
looked at the correct picture approximately 45% of the
time. Looks to the target picture then increased linearly
at a rate of 25 looks/sec to approximately 70% correct 1000 msec
after the passive sentence was finished, suggesting that children
don't 'decide' a passive is passive until they begin processing
the second N.
Eye-tracked adults. 23 college students were
faster (2280 msec vs. 2499 msec, p < .0005) and more accurate
(100% vs.96%, p < .05) on actives than passives. For
both actives and passives, adults consistently looked at the
correct picture 50% of the time until the onset of the
participle, at which point correct looks diverged for actives and
passives. For actives, correct looks increased linearly at
a rate of 75 looks/sec to approximately 80% correct during the
final noun. Correct looks remained at 80% until 300 msec
after the sentence was over. For passives, correct looks
remained at 50% until the onset of the final noun, at which point
correct looks monotonically increased at an average rate of 27
looks/sec to 90% correct 1300 msec after the sentence was
over. Factoring in time needed to program eyemovements, our
results suggest that adults can distinguish spoken actives from
passives before they hear the participle (i.e., before the
sentences are disambiguated in text). Acoustical analyses
conducted to determine how adults were able to do this revealed
that active verb stems were shorter than passive verb stems (289
msec vs. 322 msec, p < .01), the second
the
was shorter in actives than passives (64 msec vs. 92 msec, p
< .0005) and the second N was longer in actives than passives
(408 msec vs. 379 msec, p < .05). Thus, adults' early
eyemovement data probably reflects adults' ability to use the
differences in the duration of active and passive verb stems to
disambiguate actives and passives.
Discussion. The children's 55% correct looks
for actives vs. 45% looks for passives during the first half of
the sentences suggest that, upon hearing a sentence, even 5- and
6-year olds initially adopt a Bever-like "First NP as Agent"
strategy. Although they appear to distinguish between
actives and passives when they access the participle, and they
begin to correctly interpret actives at this point, children's
interpretation of passives is quite delayed and, in many cases,
appears to occur "off-line". Adults' initial looks show no
sign of a "First NP as Agent" strategy. Furthermore, adults
appear to use subtle acoustic cues to quickly disambiguate spoken
actives from passives at a point when written actives and
passives are still ambiguous. Despite this ability, adults
are somewhat faster at processing spoken actives than
passives. Existing accounts of children's and aphasic
adults processing of passives all assume that the problem is
solely due to syntactic limitations. Our eyemovement
results suggest that children's (and perhaps aphasic adults')
difficulties with passives might partly reflect an inability to
use phonetic correlates for syntactic structure in the processing
of complicated structures.
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