Either way, cognitive approaches have helped to draw attention to the importance of non-state actors – pressure groups, the media, scientists – in affecting the inter-relationship between particular frames and the institutional frameworks described above. They do so by analysing EPI as the result of either circumstances external to the policy process (sudden, unforeseen crises; exogenous shocks from outside the policy system; the gradual accumulation of worrying evidence) or the guided accumulation of relevant knowledge (‘learning’) amongst decision makers.