|
A case against chance performance: Evidence from eye movements
of agrammatic aphasics| old_uid | 6415 |
|---|
| title | A case against chance performance: Evidence from eye movements
of agrammatic aphasics |
|---|
| start_date | 2009/03/06 |
|---|
| schedule | 15h-16h30 |
|---|
| online | no |
|---|
| location_info | Pavillon de l'Enfant et de l'Adolescent, dans le batiment aller à droite, prendre l'ascenseur "monte malades", 3e étage, salle de conférence au fond à gauche |
|---|
| summary | (joint work with Sandra Hanne, Irina Sekerina, Frank Burchert, Ria De
Bleser)
Broca aphasics often perform at chance level in the comprehension of
reversible noncanonical sentences (Grodzinsky 1995, Burchert et al.
2003). The Trace-Deletion-Hypothesis (Grodzinsky 1995) argues that
patients erroneously assign thematic roles based on an agent-first
heuristic. In an eye-tracking study, Dickey et al. (2007) observed a
mismatch between aphasics’ online sentence processing and their
offline responses: While patients exhibit normal-like online
processing, they often do not succeed in offline comprehension: chance
performance in offline tasks does not necessarily reflect chance level
performance during incremental online processing. Dickey and
colleagues argue that the normal online performance of aphasics can be
explained in terms of the slowed processing hypothesis: aphasics build
structure more slowly than normals, and are therefore sometimes unable
to converge on the correct syntactic structure in time to parse the
sentence correctly.
We provide further evidence for the slowed processing account from
German. A sentence-picture-matching experiment was conducted with 8
controls and 7 German Broca aphasics. We used German canonical SVO
sentences (1) and noncanonical OVS sentences (2).
(1) Der Sohn fängt den Vater.
(2) Den Sohn fängt der Vater.
Two pictures were presented side-by-side simultaneously with the
spoken sentence: the target (agent and patient acting according to the
sentence) and the foil picture (semantically reversed action).
Accuracy, reaction times and eye-movements were recorded.
For accuracy, controls were at ceiling for both conditions (SVO: 98%,
OVS: 95%) while patients were impaired for SVO (80%) and at chance for
OVS (46%). Patients were twice as slow as controls but SVO was
processed faster than OVS in both groups. Controls’ eye movements
reflected a preference for the target picture from the der/den-NP
region onwards in both conditions. Patients’ fixation patterns in the
canonical SVO condition were very similar. When we analyzed all trials
(correct and wrong ones) for the noncanonical OVS condition, we
observed a persistent preference for the foil picture. This might
suggest the application of an agent-first heuristic. Following Dickey
et al. (2007), we looked at correct and incorrect trials separately
and found that, in correct trials, patients (just like controls)
showed an early preference for the target picture. This is new
evidence for a dissociation between patients’ online processing and
their offline performance, similar to claims regarding children
(Sekerina et al. 2004).
In addition to the above findings, I demonstrate how individual
differences among aphasics' performance (a crucial issue that is
avoided in aphasia research) can be modeled statistically using linear
mixed effects models. |
|---|
| responsibles | Pallier |
|---|
| |
|