Group Behaviour : Generally to avoid the huge losses in competitions the firms in oligopoly market forms group. So generally we saw a group behaviour in the market but if any of the firm try to earn more profit and leave this group by decreasing the prices, then there is a possibility of the price war in the market (because the other firms will also react in the same manner in order to save their share in the market). But as the firms receives huge losses from price-war, they again unites and forms group.
Interdependence of Firms : All the firms operating in oligopoly market are interdependent on each other. Every firm can affect the other firm and can be affected by other firms. Therefore every firm studies the policies of other firms and then decides their price and output policies according to it (whether it is price policy or product policy or stock policy or sale promotion policy, etc.). For example if any firm changes their price policy then other rival firms will also changes their price policy accordingly.
