Friendship was important to Stalin, and he used it to gain and maintain power. Kotkin observed that Stalin "generally gravitated to people like himself: parvenu intelligentsia of humble background". He gave nicknames to his favourites, for instance referring to Yezhov as "my blackberry". Stalin was sociable and enjoyed a joke. According to Montefiore, Stalin's friendships "meandered between love, admiration, and venomous jealousy". While head of the Soviet Union he remained in contact with many of his old friends in Georgia, sending them letters and gifts of money.