The Power of the Like in Adolescence: Effects of Peer Influence on Neural and Behavioral Responses to Social Media

Abstract

We investigated a unique way in which adolescent peer influence occurs on social media. We developed a novel functional MRI (fMRI) paradigm to simulate Instagram, a popular social photo-sharing tool, and measured adolescents' behavioral and neural responses to likes, a quantifiable form of social endorsement and potential source of peer influence. Adolescents underwent fMRI while viewing photos ostensibly submitted to Instagram. They were more likely to like photos depicted with many likes than photos with few likes; this finding showed the influence of virtual peer endorsement and held for both neutral photos and photos of risky behaviors (e.g., drinking, smoking). Viewing photos with many (compared with few) likes was associated with greater activity in neural regions implicated in reward processing, social cognition, imitation, and attention. Furthermore, when adolescents viewed risky photos (as opposed to neutral photos), activation in the cognitive-control network decreased. These findings highlight possible mechanisms underlying peer influence during adolescence.

Keywords: adolescent development; neuroimaging; open materials; risk taking; social cognition; social influences.

Fig. 1.

Two examples of stimuli presented during the imaging paradigm. Participants saw innocuous photos of adolescents or everyday objects (e.g., the coffee drinks on the left) or images of objects related to risky behavior (e.g., the marijuana cigarette on the right) or adolescents engaging in risky behaviors. Images appeared as they would have in the Instagram app on a smartphone in the year 2014: The number of likes was displayed underneath each photo next to a heart icon, and the Instagram menu buttons were displayed beneath the likes. Finally, there were two buttons allowing participants to like an image (“♥Like”) or to move on without liking the image (“→Next”).

Fig. 2.

Neural responses to Instagram photos with many likes compared with photos with few likes. The brain maps in (a) show neural regions with significant activity (z > 2.3, cluster corrected at p < .05) for the many likes > few likes contrast, for each of the three types of photos. The brain maps in (b) show neural regions with significant activity (z > 2.3, cluster corrected at p < .05) for the risky > neutral contrast and the risky < neutral contrast. Brain images are shown by radiological convention (i.e., left side of the brain is on the right). The brain map in (c) shows the location of the region of interest in the nucleus accumbens that was identified using a monetary-incentive-delay task in an independent sample of young adults (Tamir & Mitchell, 2012).