The Massim hold animistic beliefs believing that spirits inhabit trees, rocks, or areas of swamp, unusually rocky areas or springs. This is consistent with the rest of New Guinea. One difference that does stand out is the fact that the Massim area is matrilineal. The yam is the most important agricultural crop and the women continue to have a right to their family line's share of the crops coming from their families' land. This right continues even after the women marry and leave their village to live in the villages of their husbands.

      The Massim area is probably most known for a intricately developed system of exchange referred to as the "Kula". It consisted of a complicated trade system that was part ceremonial and part practical. In these island groups each important man had Kula partners. These were usually lifelong partnerships and the trading was done annually. The valuable pieces traded were extremely highly regarded and some even had personal names. No one person could accept an object of importance and take it out of the trading cycle for long - if they did they would be shunned by the rest of society. This trade cycle had numerous social benefits and is said to have replaced warfare on many occasions by creating an interdependence between groups which would most likely otherwise be at war. Shell ornaments were central in the exchange as well as stone blades. The stone blades had wooden shafts intended to set off the qualities of the blade and were of aesthetic use only. These blades and shell ornaments, some important enough to have personal names, were only owned by the most important men. These items were the most persuasive items a person could use to persuade his Kula partner to part with the objects he may want. These items were also part of a wealth display and were carried by women in ceremonial dances.

      Massim art objects emphasize two-dimensional space. From canoe prows to lime spatulas, flat decorated surfaces predominate. The strict symmetry found throughout New Guinea also exists in the Massim area, but in a more relaxed version.