The roots of polarisation in the individual reward system

Polarization in modern societies has been widely studied in the last decades. Concerns about its potential threat to democracy only expanded in the internet era where (mis)information is ubiquitous, its transmission faster than ever, and the freedom and means of opinion expressions are limitless. In the present study, we show that polarization at the group level in humans is inevitable and is a byproduct of biased processing of new information in favour of choice-confirmatory evidence. Through agent-based simulations, we show that confirmation bias in individual learning is sufficient for creating polarization at group level independently of any additional assumptions about the opinions themselves, a priori beliefs about them, information transmission mechanisms, nor the structure of social relationship between individuals. This generative process, which is compatible with polarisation mechanisms described elsewhere, constitutes an entrenched, primeval biological tendency that helps explain the extraordinary resilience of polarisation against mitigating efforts such as dramatic informational change in the environment.