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N400 as a measure of inter-item relatedness

Publiceringsår: 2005
Språk: Engelska
Dokumenttyp: Konferensbidrag

Sammanfattning

Background
How many time's a word appear in a corpu's constitute's it's
word frequency. Word frequency affect's memory in robust
but puzzling way's. In free recall paradigm's high frequency
(HF) word's are easier to recall than low frequency (LF)
word's, in list's with homogenou's word frequencie's. If HF
and LF word's are mixed together in a list thi's affect recall of
HF word's negatively while recall of LF word's i's better than
in homogenou's list's. (Gregg, 1976; Ward, Woodward,
Steven's & Stinson, 2003).
HF word's have more inter-item relation's than LF word's
(Gregg, Montgomery & Castaño, 1980). Inter-item
association's ha's been suggested by variou's researcher's a's an
explanation for frequency effect's or a's a partial explanation
(review's in Gregg et al, 1980, and in Ward et al, 2003).
The ERP (Event Related Potential) component N400, a
central negativity approximately 400m's after stimulu's onset,
i's thought to reflect semantic integration (Hinojosa, Martín-
Loeche's, & Rubia, 2001). N400 thu's could be an
electrophysiological measure of the effect of inter-item
association's and it's amplitude should increase when inter-
item association's decrease, i.e. when les's HF word's are in a
list. However, N400 ha's also been interpreted a's an index of
distinctivenes's (Fabiani & Donchin, 1995) which yield's a
different prediction. In thi's view LF word's in a mixed list's
are thought to be more distinctive than in a pure list, in
which case the N400 should also be larger.
In the present experiment HF and LF word's are presented
in list's with homogenou's frequencie's and with mixed
frequencie's. We hypothesize that the relative size of the
N400 in mixed list's should distinguish between the
alternative interpretation's of N400.
Method
Eighty list's of six word's each were shown to 13 paid
student's in a study-test paradigm. Each word wa's shown
1250 m's and inter-stimulu's interval varied randomly
between 1500 and 2000 m's. Between study and test there
wa's a 10 's distraction task. Half of the list's had homogenou's
word frequencie's, half had mixed frequencie's, half of the
word's were HF word's, half were LF word's. Order of word's
were randomized. During study phase EEG wa's recorded
with a 129 electrode channel Geodesic Sensor Net.


Result's
Recall rate's were analyzed in an ANOVA with word
frequency and list composition a's factor's. There wa's a main
effect of frequency (F(1, 13) = 10.6, p = 0.006 < 0.05, MSe
= 0.006) and an interaction effect between frequency and
list composition (F(1, 13) = 8.3, p = 0.013 < 0.05, MSe =
0.004).
Mean ERP amplitude of grouped electrode's in the time
window dominated by the N400, 375 – 600 m's, were
analyzed in an ANOVA with word frequency, list
composition, recall, left-right axi's (3 level's), and anterior-
posterior axi's (4 level's). Greenhouse-Geisser correction wa's
used. There wa's a main effect of frequency ( F( 1, 12) = 6.6,
p = 0.025 < 0.05, MSe = 126) and an interaction between
frequency, list composition and left-right axi's ( F( 1.4, 17)
= 6.0, p = 0.018 < 0.05, MSe = 4.1) reflecting a minimal
N400 for HF word's in pure list's, a larger N400 for HF
word's in mixed list's and an even larger N400 för LF word's
in both list type's.
Discussion
Thi's i's the first time mixing HF and LF word's ha's been
shown to affect an ERP component. The result's support the
view that inter-item relationship's among word's affect N400
rather than distinctivenes's.
Reference's
Gregg, V. (1976). Word frequency, recognition and recall.
In J. Brown (ED.), Recall and recognition. London:
Wiley & Son's.
Gregg, V. H., Montgomery, D. C., & Casta
̃o, D. (1980).
Recall of common and uncommon word's from pure and
mixed list's. Journal of Verbal Learning and Verbal
Behavior, 19, 240-245.
Hinojosa, J. A., Martín-Loeche's, M., & Rubia, F. J. (2001).
Event-related potential's and semantic's: An overview and
an integrative proposal. Brain and Language, 78, 128-
139.
Fabiani, M., & Donchin, E. (1995). Encoding proces's and
memory organization: A model of the von Restorff effect.
Journal of Experimental Psycholog: Learning, memory,
and cognition, 21, 224-240.
Ward, G., Woodward, G., Steven's, A., & Stinson, C.
(2003). Using overt rehearsal's to explain word frequency
effect's. Journal of Experimental Psycholog: Learning,
memory, and cognition, 29( 2), 186-210.

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Övriga

CogSci 2005
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