| |
Abstract:
We will present results from
extensive simulation studies and a series of on-line reading
experiments on Subject vs. Object RCs such as (1) to
(4).
|
(1)
|
Der Wärter, der den
Häftling beleidigt hatte, entdeckte den Tunnel.
|
|
|
The guard, who[nom] the[acc]
prisoner insulted had, discovered the tunnel.
|
|
(2)
|
The guard who had insulted the
prisoner discovered the tunnel.
|
|
(3)
|
Der Wärter, den der
Häftling beleidigt hatte, entdeckte den Tunnel.
|
|
|
The guard, who[acc] the[nom]
prisoner insulted had, discovered the tunnel.
|
|
(4)
|
The guard who the prisoner had
insulted discovered the tunnel.
|
In a recent proposal, MacDonald
& Christiansen (2002) claimed that the well established
processing difference of English Subject vs. Object RCs (King
& Just, 1991; Gibson, 1998) can be explained best by
sentences' differential degree of word order regularity, as
captured by Simple Recurrent Networks: Whereas word order in
English Subject RCs (2) resembles that of the most frequent
main clause (S-verb-O), Object RCs (4) suffer from irregular
(i.e., much less frequent) word order (O-S-verb).
Furthermore, the fact that low-reading span participants
suffer from object-extractions more than high-span readers
has been attributed to low-spans' lower degree of reading
experience, as simulated by the number of SRN training
epochs.
Our results cast serious doubt on
their interpretations. In German, in contrast to English, word
order in SRCs (1), S-O-verb, differs from main clause word
order (S-verb-O). Nevertheless, reading time data still exhibit
a clear advantage of SRCs over ORCs. We ran a series of
simulations on SRNs, keeping architecture and training
parameters as close as possible to MacDonald &
Christiansens. While we succeeded in replicating the original
data on English input, the advantage of SRCs disappeared and,
in early epochs, even reversed after switching to
German. A careful reanalysis of both the English and
German network behaviour indicated that:
-
the performance of the networks was
mainly determined by very local (2-3 words)
regularities;
-
the network failed to capture the
subject/main verb number agreement across the distance of the
embedded relative clause, even after ample training (12
epochs);
-
the network did not acquire a
notion of RC-embedding, thus misinterpreting parts of the
embedded sentence as inaccurate main clause input.
The findings suggest that
MacDonald & Christiansens main results may be simulation
artefacts. It remains an open question though whether a
more appropriate simulation setting or network architecture
will be able to account for the data.
References
Gibson, E. (1998). Linguistic complexity:
locality of syntactic dependencies. Cognition, 68,1,
1-76.
King, J., & Just, M. A. (1991). Individual
differences in syntactic processing: The role of working
memory. Journal of Memory and Language, 30, 580-602.
MacDonald, M. C., & Christiansen, M. H.
(2002). Reassessing working memory: A comment on Just and
Carpenter (1992) and Waters & Caplan (1996). Psychological
Review.
|
