ERP data from both time periods (early and late in the exposure) were
extracted for each condition and stimulus type. Response amplitudes
were calculated using a 20 ms time window around peaks observed in
group average waveforms; these took place at ~50 ms and ~150 ms
after the stimulus divergence point (second syllable onset). These latencies
correspond well to previous research showing lexical identification
as early as 50 ms post stimulus uniqueness point (MacGregor et al.,
2012) and later about 150 ms (Shtyrov et al., 2005). First, signals from
fronto-central channels Fz and FCz, where the responses were most
pronounced (Supplementary Fig. 2), were combined together. Mean
amplitudes from the two response latencies were separately submitted
to repeated measures analysis of variance (rmANOVA) with factors
Lexicality (known word vs. pseudo-word vs. non-native pseudoword)
× Attention (ignore vs. attend) × Exposure time (early vs. late in
exposure session). To investigate the effect, and its topographical
Table 2
Results of free recall and recognition tasks. Results (SEM) from ignore and attend (separated with |, respectively) conditions for native pseudo-words and known words. Mean number of
correct and incorrect responses, hit rate (HR), false alarm rate (FA), and discriminability value d′ are listed.
Correct [mean] Incorrect [mean] HR [%] FA [%] d′
Pseudo-words Free recall 0.23 (0.09) | 1.73 (0.26) 0.95 (0.23) | 3.27 (0.54) 5 (1.83) | 35 (5.29) NA NA
Recognition 1.86 (0.23) | 3.59 (0.26) 1.45 (0.32) | 1.09 (0.27) 39 (4.12) | 69 (4.43) 16 (2.83) | 13 (2.29) 0.76 (0.13) | 1.81 (0.16)
Known words Free recall 1.50 (0.22) | 3.32 (0.23) 0.45 (0.16) | 2.05 (0.45) 30 (4.31) | 66 (4.63) NA NA
Recognition 2.55 (0.25) | 4.32 (0.20) 0.91 (0.24) | 1.45 (0.23) 50 (4.86) | 80 (3.12) 11 (1.98) | 15 (2.10) 1.33 (0.19) | 2.04 (0.15)
284 L. Kimppa et al. / NeuroImage 118 (2015) 282–291
distribution in signal space more comprehensively, these were further
followed up with a similar rmANOVA applied on a larger electrode array
(see Supplementary data).