Face learning via brief real-world social interactions induces changes in face-selective brain areas and hippocampus

Abstract

Making new acquaintances requires learning to recognise previously unfamiliar faces. In the current study, we investigated this process by staging real-world social interactions between actors and the participants. Participants completed a face-matching behavioural task in which they matched photographs of the actors (whom they had yet to meet), or faces similar to the actors (henceforth called foils). Participants were then scanned using functional magnetic resonance imaging (fMRI) while viewing photographs of actors and foils. Immediately after exiting the scanner, participants met the actors for the first time and interacted with them for 10 min. On subsequent days, participants completed a second behavioural experiment and then a second fMRI scan. Prior to each session, actors again interacted with the participants for 10 min. Behavioural results showed that social interactions improved performance accuracy when matching actor photographs, but not foil photographs. The fMRI analysis revealed a difference in the neural response to actor photographs and foil photographs across all regions of interest (ROIs) only after social interactions had occurred. Our results demonstrate that short social interactions were sufficient to learn and discriminate previously unfamiliar individuals. Moreover, these learning effects were present in brain areas involved in face processing and memory.

Keywords: fMRI; face perception; perception; perceptual learning.

Figure 1.

Examples of the photographs used in the study. The four photographs on the left show one of the actors. The four photographs on the right show the foil for that actor. Note that distinguishing these two people is a difficult task for unfamiliar viewers (Hancock et al., 2000; Young & Burton, 2017).

Figure 2.

The experimental timeline. Testing took place on four separate days. During session one, participants completed the first behavioural task. During session two, participants were scanned using functional magnetic resonance imaging (fMRI). When the scan was complete, participants interacted with actors for 10 min immediately after leaving the scanner. During session three, participants interacted with the actors for 10 min and then completed the second behavioural task. During session four, participants interacted with the actors for 10 min and then completed the second fMRI scan.

Figure 3.

The timeline of the behavioural task procedure (left). Participants had to judge whether the two simultaneously presented photographs depicted the same identity or not. The presented trials represent “no”, “yes”, “no”, and “yes” trials. The timeline of the functional magnetic resonance imaging (fMRI) task procedure (right). Participants were scanned while photographs of actors or foils were presented for 3 s each. Participants were not given any instructions about the photographs. To ensure they pay attention to the stimuli, they were asked to press a response button every time the black fixation cross turned red (this occurred 30% of the time).

Figure 4.

Mean accuracy data for the behavioural face-matching task before and after social interactions had occurred. Results showed that social interactions improved performance accuracy for the actor/actor trials only. There was a significant two-way interaction between session and trial type (p < .0001). Error bars show SE of the mean across participants. *Denotes a significant difference (p < .001).

Figure 5.

Mean accuracy data for the behavioural face-matching task before and after social interactions had occurred.

Figure 6.

Percent signal change data for the actor and foil photographs before and after social interaction in the face-selective areas and the right hippocampus. We observed a significant two-way interaction (p = .012; partial η² = 0.26) between photograph type (actor and foil) and session (pre-interaction and post-interaction). This was driven by a reduction in the neural signal to foil photographs across all regions of interest (ROIs) in scan two after the real-world social interactions had occurred.