Figure 1: Behavioural results.

(a) Experimental paradigm. The social rejection and somatic pain tasks each consisted of two consecutively administered runs of eight trials (that is, 16 total trials). The order of the two tasks was counterbalanced across participants. (i) Social rejection task: each trial in the social rejection task lasted 45 s and began with a 7-s fixation cross. Subsequently, participants saw a headshot photograph of their ex-partner (‘Ex-partner’ condition) or a close friend (‘Friend’ condition) for 15 s. A cue-phrase beneath each photo directed participants to think about how they felt during their break-up experience with their ex-partner or a specific positive experience with their friend. Subsequently, participants rated how they felt using a five-point scale. To reduce carryover effects between trials, participants then performed an 18-s visuo-spatial control task in which they saw an arrow pointing left or right and were asked to indicate which direction the arrow was pointing. Ex-partner versus Friend trials were randomly presented with the constraint that no trial repeated consecutively more than twice. (ii) Somatic pain task: the structure of somatic pain trials was identical to rejection trials with the following exceptions. During the 15-s thermal stimulation period, participants viewed a fixation cross and focused on the sensations they experienced during a hot (painful) or warm (non-painful) stimulus that was delivered (1.5-s temperature ramp up/down, 12 s at peak temperature) to their left volar forearm at temperatures calibrated for each person (for details, see Methods). They then rated the pain they experienced using a five-point scale. (b) Behavioural data from trial-by-trial pain and emotion rating (n=60, eight trials for each condition). Error bars represent within-subject standard errors of the mean (s.e.m.). (c) Relative word frequency for negative emotion word categories among negative emotional words that participants used to describe the stream of thoughts while they were viewing the ex-partner’s photo in the scanner after the fMRI scanning. We used the Linguistic Inquiry and Word Count dictionary³³ (LIWC) to categorize emotional words. ***P<0.001, multi-level generalized linear model.