Opinion Herding Brains: A Core Neural Mechanism for Social Alignment Simone G. Shamay-Tsoory, 1, * Nira Saporta, 1 Inbar Z. Marton-Alper, 1 and Hila Z. Gvirts 1 When we clap our hands in synchrony, feel the sadness of a friend, or match our attitudes to peer norms, we align our behavior with others. We propose here a model that views synchronized movement, emotional contagion, and social conformity as interrelated processes that rely on shared neural networks. Building on the predictive coding framework, we suggest that social alignment is mediated by a three-component feedback loop – an error-monitoring system that reacts to misalignment, an alignment system, and a reward system that is activated when alignment is achieved. We describe herding-related syndromes (autism, loneliness) and call for innovative research to investigate the links between the levels of alignment. From Herds to Conformism Herding is ubiquitous throughout the animal kingdom. Birds fly together in flocks, schools of fish move in a coordinated manner, and swarming ants exhibit collective behavior [1]. Although group living has various benefits including foraging efficiency [2] and reduction of predation risk [3], individuals may benefit from sociality only if they remain connected to other members [4], indicating that achieving connectedness is a key motivator of behavior across species. In humans, collective action may be observed in various everyday situations including unintentional synchronized walking [5], rocking [6], and synchronized body-posture sway when conversing [7]. Notably, it is possible to observe diverse behavioral displays of group alignment that go beyond joint movement. These ‘higher-level’ behaviors may include emotional contagion and social conformity. Given these various forms of group alignment, it has been proposed that herding may be conceptualized as the tendency of an organism to align with other organisms in a group in terms of behaviors and cognitions [8]. Despite a long history of scientific investigation, we are only now beginning to decipher the different aspects of social alignment. We synthesize here disparate recent findings on movement synchrony, emotional contagion, and conformity under a single conceptual umbrella: a social alignment model. We propose that these seemingly different behavioral manifestations of herding are actually linked, influencing one another in a reciprocal manner and adhering to similar principles. We advocate in favor of a common set of brain networks underlying social alignment and hypothesize that, at its core, this system enables connectedness between individuals. The Various Levels of Herding are Behaviorally Linked Interpersonal motor synchrony involves the alignment in time of the behavior of two or more interacting individuals. Close to the constructs of mimicry or imitation, motor synchronization also introduces the importance of coordination in the timing of the action [9]. Synchronization can occur implicitly (coordination of walking pace in humans) but can also occur explicitly (soldiers marching [10]). Emotional contagion represents the alignment of one’s emotions with the emotions expressed by those around you, whether consciously or unconsciously [11]. Emotional contagion may Highlights Traditionally, the diverse behaviors that involve social alignment have been considered individually. We synthesize models of collective action across species with an emer- ging body of neuroscience, neurocom- putational, and psychology research to propose that different manifestations of social alignment are actually linked, with motor synchrony, emotional align- ment, and conformity influencing one another in a reciprocal manner. Building on the predictive coding fra- mework, we argue that these different levels of alignment reflect the workings of a prototype feedback-loop model. The social alignment feedback loop includes three core components. One system is in place to react to alignment, and another system reacts to misalignment. Based on the misa- lignment detected, a further system is responsible for aligning to the point of perceived alignment. 1 Department of Psychology, University of Haifa, Haifa 3498838, Israel *Correspondence: sshamay@psy.haifa.ac.il (S.G. Shamay-Tsoory). TICS 1879 No. of Pages 13 Trends in Cognitive Sciences, Month Year, Vol. xx, No. yy https://doi.org/10.1016/j.tics.2019.01.002 1 © 2019 Elsevier Ltd. All rights reserved.