A brain network that supports consensus-seeking and conflict-resolving of college couples' shopping interaction

Abstract

One of the typical campus scenes is the social interaction between college couples, and the lesson couples must keep learning is to adapt to each other. This fMRI study investigated the shopping interactions of 30 college couples, one lying inside and the other outside the scanner, beholding the same item from two connected PCs, making preference ratings and subsequent buy/not-buy decisions. The behavioral results showed the clear modulation of significant others' preferences onto one's own decisions, and the contrast of the "shop-together vs. shop-alone", and the "congruent (both liked or disliked the item, 68%) vs. incongruent (one liked but the other disliked, and vice versa)" together trials, both revealed bilateral temporal parietal junction (TPJ) among other reward-related regions, likely reflecting mentalizing during preference harmony. Moreover, when contrasting "own-high/other-low vs. own-low/other-high" incongruent trials, left anterior inferior parietal lobule (l-aIPL) was parametrically mapped, and the "yield (e.g., own-high/not-buy) vs. insist (e.g., own-low/not-buy)" modulation further revealed left lateral-IPL (l-lIPL), together with left TPJ forming a local social decision network that was further constrained by the mediation analysis among left TPJ-lIPL-aIPL. In sum, these results exemplify, via the two-person fMRI, the neural substrate of shopping interactions between couples.

Figure 1

Experimental design. Two types of shopping contexts were designed to examine how significant others’ preferences affect one’s own shopping decisions. After 1 s of fixation cross with arrows indicating alone/together shopping at the beginning of each trial, stimulus was presented with the price. During 6 s of evaluation time, participants give preference ratings from 1 (dislike most) to 4 (like most). Then the two screens would show either one’s own rating or own-plus-other ratings for a jittered interval (3–6 s). Subsequently, both a ‘checked’ and a ‘X’ mark would appear in the lowest part of the screen, cueing the beginning for response period (up to 2 s). Each participant’s responses would be recorded and displayed independently by a ‘purchased’ or ‘not-purchased’ sign.

Figure 2

Behavioral analysis results. The comparison of buying ratio between alone and together condition, the modulatory effect of significant other’s preference was observed by increasing one’s buying decision significantly when partner’s preference was high (3 or 4), and decreasing one’s buying decision when partner’s preference was low (1 or 2) compared to shopping alone. The two-way ANOVA showed significant differences between shop-alone vs. shop-together as follows: across other’s preference: 1 (F(4,171) = 3.85, p < 0.005); 2 (F(4,184) = 7.83, p < 10^–4); 3 (F(4,184) = 16.77, p < 10^–5); 4 (F(4,145) = 6.01, p < 10^–4. The female and male participants did not differ significantly in preference nor in shopping decisions (both p > 0.05).

Figure 3

GLM analysis results. The brain regions engaged in together > alone (left) and congruent > incongruent (right) contrasts. The bilateral TPJ, STG, ventral striatum, PCC, and dmPFC were commonly involved in shopping together than alone, in turn, ‘congruent > incongruent’ contrast defined by chosen preferences in two categories (high = 3,4/low = 1,2) revealed brain regions such as bilateral TPJ, insular, putamen, and PCC/precuneus for congruent (same rating categories), and SFG for incongruent (different rating categories) condition. The contrasts are thresholded at p < 0.01 (Left) and p < 0.05 (Right), and FWE corrected at p < 0.05.

Figure 4

Parametric modulation results. The parametric modulation of preference differences (left) and decision changes (right) in incongruent condition. The preference differences were parameterized by subtracting preferences between own and others in own-high/other-low, recruiting left anterior IPL, or own-low/other-high cases, in PCC. The decision changes were further encoded by multiplying the decision (buy/not-buy) toward own preference (insisting) or other preference (yielding) to preference differences, only the left lateral IPL activations were positively correlated. The trial estimate beta coefficient (β) extracted from the left IPL were averaged and plotted across insisting (− 3) to yielding (3) to show parametric relations (bottom right). The surface map of preference differences was thresholded at p < 0.05, FWE corrected and decision change was thresholded at p < 0.01, k = 20 (uncorrected).

Figure 5

PPI results. The functional connectivity of four different seed regions in ‘incongruent > congruent’ contrast. The left TPJ (pink) are connected to bilateral vmPFC, dmPFC, middle frontal gyrus (pink dotted line), the right TPJ (pink) are connected to bilateral STG/STS and right NAcc (violet dotted line), the left lateral IPL (yellow) are connected to bilateral mPFC, dmPFC, left superior frontal gyrus, insular. The anterior IPL (green) was connected to bilateral cuneus. All the surface brain map was shown in p < 0.05, FWE corrected. And the PPI was conducted separately for each seed region and overlaid later for visualization, the individual results are provided in supplementary information.

Figure 6

Mediation analysis results. The subject-level effective relationship during ‘together > alone’ between three ROIs, the left anterior IPL (l-aIPL, green), lateral IPL (l-lIPL, yellow), and TPJ (pink) (left), are shown in two different subsequent ways (right). In the causal model from l-aIPL to TPJ (c1, outward triangle denoted by lines), or from TPJ to l-aIPL (c2, inward triangle denoted by dotted lines), the total effect is significant (c1 and c2, ***p < 0.001) as well as the direct path of models (c1′ and c2′, *p < 0.028). However, the mediatory role of l-lIPL (a*b) was significant in only one way: from l-aIPL to TPJ (indirect path, a*b1 (a-lIPL to TPJ), **p = 0.002). Meanwhile, neither effects of mediation (indirect path, a*b2 (TPJ to a-lIPL), p = 0.301) nor path from l-lIPL to l-aIPL (b2, p = 0.309) was significant in the second causal model (TPJ–l-lIPL–l-aIPL).