1. Introduction. Research using the event-related potential (ERP) technique has provided many important insights into the neural mechanisms associated with language comprehension. The integration of lexico-semantic information is associated with an increased centro-parietal negativity between 300-500 ms known as the N400 (Kutas & Federmeier, 2011; Kutas & Hillyard 1980). Morphosyntactic integration is associated with an early left anterior negativity (LAN) maximal around 200-500 ms, followed by a late posterior positivity (P600) maximal between 500 and 800 ms (see Kutas, Van Petten & Kluender (2005) for review). The P600, in absence of early negativity, is also elicited by well-formed sentences that present increased difficulty due to temporary ambiguity (i.e. garden-paths; Gouvea, Phillips, Kazanina & Poeppel, 2010; Osterhout, Holcomb & Swinney, 1994). The use of ERP as a means of indexing the different neural mechanisms associated with language processing is contingent on the assumption that all neurologically normal, native speakers show consistent responses to sentence stimuli such that the grand averaged ERPs reflect effects that are manifest uniformly across individuals. This notion was recently challenged by Tanner and Van Hell (2014). In their innovative study, they showed that, although in the grand mean syntactic violations elicited a classic biphasic LAN/P600 response, most participants either showed an N400 or a P600 rather than a biphasic response. Given the topographical distribution of the effects for each group, they concluded that the LAN often found for syntactic violations in grand mean analyses is the result of the distributed negativity in some subjects being neutralized or minimized by the right lateralized positivity in the others such that only the left anterior negativity remains. Response dominance did not, however, predict acceptability judgment accuracy, nor did it correlate with measures of working memory (WM) and executive control. The individual differences in N400/P600 response dominance observed by Tanner and Van Hell (2014) lead to interesting questions regarding other contexts which tend to elicit these potentials. Garden-path sentences are known to elicit P600 effects in absence of early effects but there is some variability (Friederici, Mecklinger, Spencer, Steinhauer & Donchin, 2001; Gouvea et al., 2010; Horberg, Koptjevskaja-Tamm & Kallionen, 2013; Matzke, Mai, Nager, Russeler & Munte, 2002; Vos, Gunter, Schriefers & Friederici, 2001). This variablity could suggest the possibility of individual differences in response profiles, as Tanner and Van Hell (2014) found for syntactic violations. One known source of variability in garden-path effects for both P600s and comprehension accuracy is working memory capacity (WMC). High WMC individuals show greater P600 effects for garden-path sentences compared to low WMC individuals (Friederici, Steinhauer, Mecklinger, & Meyer, 1998). High WMC individuals also show reduced garden-path effects in comprehension accuracy such that they have better comprehension accuracy for garden-paths (Just & Carpenter, 1992). Lower comprehension accuracy in low WMC individuals indicates they are more likely to arrive at “Good Enough” interpretations (Ferreira, Bailey & Ferraro, 2002) in which the faithful interpretation of the sentence is not adopted. In the current study we applied the RDI analysis to the ERPs associated with garden-path sentences in order to determine (1) if participants’ N400/P600 dominance for garden-path sentences will fall into a continuum such that there will be a continuous distribution of N400 and P600 effect magnitudes with negative correlations between them, (2) if response dominance will predict comprehension accuracy, and (3), if so, is that effect reducible to individual differences in WMC. 2. Methods.2.1. Participants. Data were collected from 62 right handed participants, 25 of which were excluded due to eligibility issues, technical issues, noncompliance, or excessive artifacts. As a result, 37 participants (20 female) between the ages of 18 and 35 (M = 21.6, SD = 3.21) were included in the analysis. All participants were right-handed, neurologically normal, native speakers of English with normal or corrected-to-normal vision, and none had had started learning a second language before age 12.2.2. Sentence Stimuli This experiment used the same control and garden-path sentences as O’Rourke & Colflesh (2014) (based on Gouvea et al., 2010). See sentences (1) and (2) for examples of garden-path and control sentences, respectively.The patient met the doctor and the nurse with the white dress showed the chart during the meeting.The patient met the doctor while the nurse with the white dress showed the chart during the meeting.There were 36 sentences per condition and an additional 288 sentences including fillers and conditions not presented herein. Fifty percent of the sentences were followed by a yes/no comprehension question. 2.3. Complex Span Tasks. As indices of WMC, three complex span tasks were used in the current study: reading span (Daneman & Carpenter, 1980; Unsworth, Heitz, Schrock & Engle, 2005), operation span (Unsworth, et al., 2005), and symmetry span (Unsworth, Redick, Heitz, Broadway, & Engle, 2009). In the reading span task participants were presented with a series of sentences and asked to indicate, via button press, if the sentence they read made sense. After each sentence they were then presented with a letter that they were to remember for later recall. At the end of the sequence, they had to recall the letters in serial order. Their score reflects the total number of letters recalled in the correct serial position out of a total of 75 items. Operation span was identical to reading span as described above except instead of making sense judgments on sentences, participants had to read math...