Pro-environmental behaviours are behaviours which are thought to benefit the natural environment (including personal buying behaviour, travel behaviour, recycling, and active participation in pro-environmental organisations). People differ in the degree to which they exhibit these behaviours. Various models have been used to explain pro-environmental behaviours, with varying degrees of success. One model proposes that environmental concerns are determined partly by three types of value: egoistic, or self; altruistic, or other people; and biospheric, or other species. A comparison of environmental concern scales, and of whether the three-value structure holds in a UK population, has recently been published. That research is continuing. Other research with respect to pro-environmental behaviour includes gender differences, self-identify, attitudes, and beliefs.