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N400 responses to proverbs: group findings versus single case effects
Poster Session E, Sunday, September 14, 11:00 am - 12:30 pm, Field House
Johanna Kissler1,2, Sebastian Geukes1, Vicky Everding1; 1Bielefeld University, Department of Psychology, 2Bielefeld University, CRC Linguistic Creativity
Proverbs are commonly known statements that express an advice or perceived truth. Because they are so frequently encountered, it is easy for participants with intact semantic language processing to recognize them and to detect deviating endings. Hence, they could be well-suited to study semantic processing in clinical populations, e.g., with the N400 paradigm. Nevertheless, few studies have investigated electrophysiological correlates of proverb processing. Almost none have looked at the detectability of the proverb N400 at the single-subject level. Here, we recorded ERPs while 33 healthy participants listened to common German proverbs. These had either correct endings (1) or one of two types of incorrect endings: semantically possible (2) or semantically inadequate (nonsense) endings (3). In the group analysis, we found large N400 effects with expected centro-parietal topography when comparing correct with possible or nonsense endings, but no difference in brain responses between the possible and nonsense endings. In a further analysis, we assessed the presence of the N400 at the single-subject level using a t-test and a cluster-permutation method. Depending on the method used (t-test vs. cluster permutation) and the contrast chosen (nonsense – correct, possible – correct), only between 33.3 and 63.3% of participants were identified as having a significant N400 effect, despite almost all having a numerically negative condition difference. Our results show that proverb violations are indeed suited to elicit large N400 effects on the group level. Moreover, interestingly proverbs induce very strong and specific predictions that are not even partially met by other semantically plausible endings constraining theories on the functional significance of the N400. At the same time, current single-subject analysis methods are not statistically powerful enough to reveal an N400 in each awake and neurologically intact participants, limiting its potential as a reliable clinical indicator. We will discuss ways to improve power for these single-subject analyses.
Topic Areas: Meaning: Lexical Semantics, Meaning: Discourse and Pragmatics