Teachers who use educational toys in classroom settings try to identify toys that will be appropriate to a child's developmental level, existing skills, and interests. They try to engage children with toys in ways that support cognitive development. Many educators emphasize the importance of open-ended imaginative play, exploration and social engagement. Toys with the quality of open-endedness can be used by children in a variety of ways and at different ages and developmental levels. Educational toys vary widely in terms of their open-endedness and their potential for exploration, imaginative play, and social engagement. Play theorist Brian Sutton Smith, who advocates for free play, has asserted that "the plans of the playful imagination dominate the objects or the toys, not the other way around." Toys whose design is more heavily specified and restricted may be less intuitive for children to use, and require more engagement and support from adults. Many studies of educational toys report that the effectiveness of a toy is more related to the involvement and guidance of adults, or to the child's intellectual level, than to the toy itself.