3.2.1. Lure-evoked N2pc

Lure-evoked contralateral–ipsilateral di fferences from posterior–lateral sites |PO7–PO8| are displayed in Figure 3. There is obviously a negative component (N2pc) peaking around 250 ms with the 1st lure. N2pc was measured by computing mean amplitudes at 200–300 ms and submitting these values to ANOVA with the factors Lure Type (color, digit) and Serial Position (1st, 2nd, 3rd lure).

**Figure 3.** Contralateral–ipsilateral event-related potential (ERP) di fferences evoked by the lures. Data are grand means across participants, recorded from left and right posterior sites PO7 and PO8. Depicted are di fferences between lure-trials and corresponding epochs of no-lure trials. Unit on x-axis is milliseconds, time-point zero is lure onset. Unit on y-axis is microvolts, negative voltage is plotted upwards. Waveforms evoked by the 1st lure are shown as solid lines, by the 2nd lure as dashed lines, and by the 3rd lure as dotted lines. ERPs evoked by color lures and digit lures are plotted with blue and grey lines, respectively. The scalp maps show the view on the head (120◦) from above. Recording sites (small circles) are depicted on one hemisphere only because the contralateral–ipsilateral di fferences were pooled across left and right sides. Blue is contralateral negativity, red is positivity. Scale is ±4 μV. Displayed are topographic distributions of N2pc evoked by the first lure at its peak latency: 256 ms with the first color lure, 224 ms with the first digit lure.

Overall, N2pc was largest with the 1st lure (Serial Position: *<sup>F</sup>*2,26 = 12.4, *p* = 0.001) and larger with color than digit lures, *<sup>F</sup>*1,13 = 4.8, *p* = 0.048. Both factors tended to interact, *<sup>F</sup>*2,26 = 3.4, *p* = 0.07. Indeed, in separate analyses for each serial position, Lure Type was significant at the first position only. *<sup>F</sup>*1,13 = 5.5, *p* = 0.04 ( *<sup>F</sup>*1,13 ≤ 2.0, n.s., for 2nd and 3rd positions). In separate analyses of the two lure types, the Position e ffect was significant in either analysis, though being somewhat larger with color lures (*F*2,26 = 9.2, *p* = 0.004) than with digit lures (*F*2,26 = 6.1, *p* = 0.009).

It may be suggested that the early negative deflections in the 2nd position waveforms, peaking at about 170 ms, are accelerated N2pc peaks. But a second peak is visible at about 250 ms in these waveforms as well. Given that attention was already shifted towards the lure stream because of the first lure, we agree with one reviewer of this paper that the negativity may reflect increased N1 components

evoked by this attended lure stream (e.g., [31]) rather than an early N2pc. When quantifying this early activity as mean amplitudes 150–200 ms, there was no e ffect of Lure Type, *F* ≤ 2.1, n.s., but a distinct effect of Position, *<sup>F</sup>*1,13 = 11.7, *p* < 0.001, with largest values for the 2nd position.
