There appeared to be a limited recognition amongst the participants of the specific psychological theories that can be seen to explain the beneficial outcomes of Intensive Interaction. The participants were found to differ in how they explained the approach and typically used everyday 'non-psychological' language or individual concepts/terms rather than clearly or extensively referencing particular theoretical models. The participants appeared to differ in the range of clients who they thought might benefit from Intensive Interaction. An Intensive Interaction Special Interest Group, which includes clinical psychologists, should be set up to instigate psychologically informed theory development and research with the broader aims of fostering greater understanding and adoption of Intensive Interaction within services for people with severe or profound intellectual disabilities and/or autism.