“…Social networks are crucial for the sharing of information and the spread of learned behaviours (Coleman, Katz & Menzel, 1957;Jackson, 2008;Jippes, Achterkamp, Brand, Kiewiet, Pols & van Engelen, 2010). However the ability to distinguish between peer influence and homophily becomes important when trying to measure accurately how much similarity on specific outcomes such as smoking behaviour (Mercken, Snijders, Steglick, Vartiainen & de Vries, 2010), obesity (Christakis & Fowler, 2007), happiness (Fowler & Christakis, 2008), loneliness (Cacioppo, Fowler, Christakis, 2009) or academic grades is due to the influence of peers.…”