How do the hierarchical levels of premises affect category-based induction: diverging effects from the P300 and N400

Abstract

Although a number of studies have explored the time course of category-based induction, little is known about how the hierarchical levels (superordinate, basic, subordinate) of premises affect category-based induction. The EEG data were recorded when nineteen healthy human participants were performing a simplified category-based induction task. The ERP results showed that: in the subordinate conclusion condition, the basic premise elicited a larger N400, versus the superordinate promise; in the basic conclusion condition, the superordinate promise elicited a larger P300 relative to both the basic premise and subordinate premise; in the superordinate conclusion condition, however, no difference was found between different promise. Furthermore, the process that reasoning from a higher level to a lower level evoked a larger P300, compared to it did in the reverse direction. The divergent evidence suggested that category-based induction at superordinate, basic, and subordinate levels might be affected by various factors, such as abstract level, direction, and distance between premise and conclusion, which yielded new insights into the neural underpinnings of category-based induction with different inductive strengths.

Figure 1

Experimental procedure of the categorisation reasoning task and behavioural performance. Top: A representative sequence and the detailed timing of one trial. Note that the illustration depicted a subordinate-basic categorisation. Moreover, ‘sparrow’ was a typical representation of ‘bird’. Bottom left: The mean RT in the conclusion items. It was notable that RT results did not reveal significant difference among the subordinate-subordinate, basic-subordinate, superordinate-subordinate, subordinate-basic, basic-basic, superordinate-basic, basic-superordinate, and subordinate-superordinate categorizations, p > 0.05 (one-way repeated-measures ANOVA). Bottom right: The accuracy of positive judgment in the conclusion items. The results revealed significant difference among the eight categorizations, p < 0.001 (one-way repeated-measures ANOVA). Note: In the bottom panel, *p < 0.05, **p < 0.01, and p < 0.001, respectively, N = 19. RT is response time; For each trial type, error bars represent ± SEM across all participants.

Figure 2

Group-level average ERPs, mean amplitudes, and scalp topographies of N400 and P300 waves. Panel A (Top): The grand-average ERP waveforms measured at the centro-frontal region [(Fz + F1 + F2 + FCz + FC1 + FC2)/6] for the subordinate-subordinate, basic-subordinate, superordinate-subordinate, subordinate-basic, basic-basic, superordinate-basic, basic-superordinate, and subordinate-superordinate categorisations. Note that when the conclusion items were subordinate categorisations, N400 amplitudes were modulated by the categorisations of premise items (subordinate, basic, and superordinate) in the time window from 0.29–0.41 s (outlined by the grey rectangle). Panel A (Bottom): The grand-average ERP waveforms measured at the centro-parietal region [(CP1 + CPz + CP2 + P1 + Pz + P2)/6] for the eight trial types. It is notable that when the conclusion items belonged to basic level categorisations, P300 amplitudes were modulated by the categorisations of premise items (subordinate, basic, and superordinate) in the time window from 0.24–0.41 s (outlined by the grey rectangle). However, when the conclusion items belonged to superordinate categorisations, neither N400 nor P300 amplitudes were modulated by the categorisations of premise item (subordinate and basic). X-axis, time (s); Y-axis, amplitude (μV). The vertical bars indicate the onsets of conclusion items. The inlayed histograms intuitively show the N400 and P300 amplitudes as indicated by the grey arrows. Error bars indicate ± 1 standard error of the mean (SEMs). Note: *p < 0.05 and **p < 0.01, respectively, N = 19. Panel B shows the scalp topographies of N400 (averaged within 0.29–0.41 s) and P300 (averaged within 0.24–0.41 s) for the eight trial types, respectively. Noteworthy was that the scalp topographies of N400 and P300 displayed clear centro-frontal and centro-parietal distributions (marked in white) for all trial types, respectively. Note: ‘Amp’ is amplitude.

Figure 3

Illustration of P300 amplitudes to reveal the direction effect of categorisations. It was notable that modulation of P300 amplitudes in the centrol-parietal region in the time widow of 0.24–0.41 s after the onsets of the conclusion items revealed the obvious direction effect in categorisations. Note: Error bars indicate ± 1 standard error of the mean (SEMs), *p*p < 0.05, **p < 0.01. N = 19.