ERPs: Semantic Incongruity

Overall, ERPs of the semantic conditions included 4,564 trials for averaging. Due to blink and drift-artefacts 695 trials (15.22%) had to be excluded from analysis. Figure 4.9 illustrates the grand average difference ERP waves for native speakers and L2 learners.72

ERP waves are depicted in a 1,600 ms time-window. The presentation of the critical item is linked to 0 ms. Electrodes are pooled into six ROIs in accordance with their location on the scalp (see Chapter 3.4.3 and Footnote 59). Voltage difference maps are presented by Figure 4.10. They illustrate the mean voltage difference between the ERP

68 _{According to the accuracy rates elicited by L2 learners, a data loss of approx. 27% has to be considered} when removing all inaccurately rated sentences. Therefore, RT data was additionally analysed, including all data points in the model: This additional analysis only reveals a significant main effect for proficiency (F(1,3381) = 3.93, p = .04, reported for denominators upper bound), indicating faster judgments as

proficiency improves. AoA does not show any influence. 69_{Denominator lower bound = 2187, p = .3.}

70_{Denominator lower bound = 2187, p = .05.} 71_{Denominator lower bound = 2187, p = .05.}

72 _{Grand average difference was calculated on the basis of the mean voltage of the congruent condition} subtracted from the mean voltage of the incongruent condition.

75

4. Results Experiment 1: Semantic Incongruity

waves of the two conditions in a 400–500 ms time-window. For sole visual purposes L2 learners are grouped on the basis of their AoA—i.e., early (< 8) vs. late (≥ 8)73_—and

their proficiency level which was determined by the C-Test score (high (≤ 80%) vs. low (> 80%))74_{. This yields three L2 learner groups, namely: early L2 learners with high}

proficiency (EAHP), late L2 learners with high proficiency (LAHP), and late L2 learners with low proficiency (LALP). Importantly, the linear mixed effects model does not include group as a factor. Single group ERPs illustrating the comparison between both

congruent and incongruent conditions are given in appendix 1.1.

Figure 4.10: Difference wave forms of grand average ERPs time-locked to the critical direct object NP according to the Congruity conditions displayed for four groups separated only for visual purpose: black = native speakers, red = EAHP, blue = LAHP and green = LALP. Voltages are plotted on y-axis ranging from -5µV to +5µV. Time array is plotted on x-axis and ranges from -100 to 1500 ms. Stimulus onset occurred at 0 ms. ROIs are labelled accordingly. Negative voltages are plotted up.

73 _{The distinction between early and late AoA is adopted from Meisel (2011, pp. 202) and applied for} visual purpose only. The present investigations treat AoA as a continuous factor.

74 _{The distinction between high and low proficiency infers the categorization in accordance with the} CEFR—i.e., advanced and intermediate, respectively (see Chapter 1). This categorization, again, is applied for visual purpose only. The present investigations treat proficiency as a continuous factor.

midline-anterior midline-posterior right-anterior right-posterior left-anterior left-posterior ms 0 500 1000 µV -2 0 2 4 ms 0 500 1000 µV -2 0 2 4 ms 0 500 1000 µV -2 0 2 4 ms 0 500 1000 µV -2 0 2 4 ms 0 500 1000 µV -2 0 2 4 ms 0 500 1000 µV -2 0 2 4 76

4. Results Experiment 1: Semantic Incongruity Native Speakers AoA = 0 proficiency > 80 EAHP AoA < 8 proficiency > 80 LAHP AoA ≥ 8 proficiency > 80 LALP AoA ≥ 8 proficiency ≤ 80

Figure 4.11: Difference voltage maps illustrating the mean differences of grand average ERPs time-locked to the critical direct object NP according to the Congruity conditions in the time- window 400–500 ms post stimulus. Differences are displayed for four groups separated only for visual purpose. Groups are indexed at the upper row of each column. Time range representing the average voltage difference for each head is labelled accordingly. Difference voltage range is plotted from -5µV (dark blue) to +5µV (dark red).

Visual inspection of Figure 4.9 and Figure 4.10 reveals an enhanced negativity for native speakers and all L2 learner groups. This negativity appears strongest between 400 and 500 ms. Differences across groups superficially appear with regard to the distribution rather than the strength and latency of the negativity. Native speakers’ negativity appears the strongest on central scalp sites with a right-lateral bias. EAHP shows largest negativities on central and left-lateralized ROIs. For LAHP, the negativity seems to be more frontally distributed, while LALP shows a rather central negativity. Latency differences are not clearly observable. Statistical analyses are carried out for the time- window between 400 and 500 ms, where the negativity seems the strongest for all groups. The time-window is analysed separately for native speakers and L2 learners (see below). See Chapter 3.4.4 for a detailed description of the mixed-effects models. AoA and proficiency did not enter the model performed to analyse the native speaker’s ERP data.

4. Results Experiment 1: Semantic Incongruity

4.2.3.1 Time-Window: 400–500 ms

Statistical results of native speakers’ ERPs reveal a main effect for ROI (F(5,758) =

32.11, p < .001)75_{. The mean potentials are more negative on anterior than posterior}

ROIs. Visual inspection indicates an effect for Congruity; however, this impression fails to reach statistical significance. The original (and most complex) statistical model shows a marginal trend for Congruity (F(1,780) = 3.28, p = .07)76_{, but it lacks statistical}

reliability. Moreover, the interaction with ROI does not yield reliability either (F(5,780)

< 1)77_{. Although Congruity and its interaction as a fixed effect were removed from the}

model, the post hoc analyses of separate ROIs were performed due to planned

comparisons. Single ROI analyses reveal a significant effect for Congruity only in the right-posterior ROI (F(1,137) = 5.05, p = .03)78_{. The detailed statistical analyses of}

single ROIs are given in appendix 2. Despite the fact that this is not a very sufficient result, it still approaches native-like processing of semantic incongruity and will be seen as an instance of the N400 effect. Possible reasons for the statistical absence of a broader Congruity effect in native speakers’ ERPs are discussed in Chapter 4.2.4 below.

Table 4-3: ANOVA table of the average ERP amplitudes in the time-window 400–500 ms conducted for L2 learners according to the Congruity conditions (denominator upper bound df = 2257, denominator lower bound df = 2077).

COEFFICIENTS _{df sum Sq mean Sq F-value upper p lower p}

CONGRUITY 1 8.00 8.00 8.42 < .001 < .001

ROI 1 148.28 29.66 30.55 < .001 < .001

AOA 1 0.93 0.93 < 1

CONGRUITY×ROI 5 16.51 3.3 3.4 < .001 < .001

ROI×AOA 5 17.74 3.55 3.65 < .001 < .001

The statistical results for L2 learners’ ERPs are displayed in Table 4-3. A global analysis reveals a significant main effect for Congruity (-0.84µV), indicating that the mean

voltage for the incongruent condition (-0.47µV) is more negative on average than for

75_{Denominator lower bound = 596, p < .001.} 76_{Denominator lower bound = 636, p < .001.} 77_{Denominator lower bound = 636, p = .32.} 78_{Denominator lower bound = 101, p = .03.}

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4. Results Experiment 1: Semantic Incongruity

the congruent condition (0.37µV). The highly significant two-way interaction indicating distributional differences for the strength of the Congruity effect is resolved by ROIs. The results of post hoc single ROI analyses are given in Table 4-4.

Table 4-4: ANOVA table of the Congruity effect in each ROI according to the average ERP amplitudes in the time-window 400–500 ms conducted for L2 learners. Diff = Difference.

ROI denominators upper- /lower- bound

mean Diff in µV

df sum Sq mean Sq F-value upper p- value lower p- value LEFT-ANTERIOR 462/342 -0.57 1 5.48 5.48 4.33 .04 .04 MIDLINE-ANTERIOR 352/232 -1.13 1 4.14 4.14 9.67 < .001 < .001 RIGHT-ANTERIOR 469/349 -0.69 1 5.16 5.16 6.77 .01 .01 LEFT-POSTERIOR 469/349 -0.97 1 6.63 6.63 7.72 .01 .01 MIDLINE-POSTERIOR 351/231 -1.01 1 5.27 5.27 6.75 .01 .01 RIGHT-POSTERIOR 462/342 -0.83 1 6.64 6.64 7.48 .01 .01

The congruity effect is reliable on all ROIs and appears to be numerically the largest on midline-anterior electrodes. The main effects for AoA and proficiency do not reach reliability. Furthermore, they do not yield any significant influence on the strength or distribution of the Congruity effect. While the factor proficiency is completely removed from the model, increasing AoA shows influence on the distributional differences of the mean potentials: They are more negative-going on anterior than posterior ROIs. Again, this does not impact Congruity. An AoA impact is reliably found only in the left- anterior ROI (F(1,462) = 4.52, p = .03)79_{, revealing that with increasing AoA the mean}

potentials are gradually going more negative .

The average peak latency of the difference waves within this time window (400–500 ms) was determined for each participant and analysed in a linear regression analysis, including AoA and proficiency as independent factors. The results, however, do not reveal any significant effects except for the intercept.

79_{Denominator lower bound = 342, p = .03.}

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4. Results Experiment 1: Semantic Incongruity