Roley et al (2007) explained the SI theories and approach, and reviewed the work of its originator, A. Jean Ayers PhD, OTR.  Drawing on motor control theories, Ayres proposed these hypotheses that underscored her treatment approaches:
- Perceptual awareness supports and facilitates occupational engagement.
- Motor learning is influenced by, if not dependent upon, incoming sensation.
- Body awareness creates a postural model to develop visual-motor skills.
- Postural control is essential for skilled academic and motor performance.
- Tactile, vestibular, PPC, and visual systems are key contributors to the development of reading and writing skills.
- The ability to focus and maintain attention and to keep a steady level of activity is related to the way in which the nervous system responds to tactile sensation.
- The sensory systems develop in an integrated and dependent manner.
- Visual and auditory processing depend on foundational body-centered senses.
The SI approach requires that qualified professionals implement these principles (among others): 
- Therapy takes place in a safe environment that includes equipment that will provide vestibular, PPC, and tactile sensations and opportunities for developing coordinated movements.
- Activities are rich in sensation (especially vestibular, tactile, and PPC sensation), and offer opportunities for integrating that information with other sensations, such as visual and auditory.
- Activities promote optimal postural control in the body, oral-motor, ocular-motor areas, and bilateral motor control, including maintaining control while moving through space and adjusting posture in response to changes in the center of gravity.
- Intervention strategies provide the “just-right challenge.”
- Opportunities exist for the client to make adaptive responses to changing and increasingly complex environmental demands. Highlighted in the Ayres Sensory Integration intervention principles is the “somatomotor adaptive response,” which means that the person is adaptive with the whole body, moving and interacting with people and things in the three-dimensional space.
Evidence supporting SI Therapy:
May-Benson TA, Koomar JA. 2010. Systematic review of the research evidence examining the effectiveness of interventions using a sensory integrative approach for children. Am J Occup Ther. 64(3): 403-14.
Lane SJ, Schaaf RC. 2010. Examining the neuroscience evidence for sensory-driven neuroplasticity: implications for sensory-based occupational therapy for children and adolescents. Am J Occup Ther. 64(3):375-390.
Obstacles to research on SI Therapy:
Paucity of doctorate trained clinicians and researchers in occupational therapy, and the inherent heterogeneity of the population of children affected by sensory integrative dysfunction. Schaaf RC1, Miller LJ. 2005.
Occupational therapy using a sensory integrative approach for children with developmental disabilities. Ment Retard Dev Disabil Res Rev. 11(2):143-148.
 Roley SS, Mailloux Z, et al. 2007. Understanding Ayers Sensory Integration. OT Practice. 12(17): CE-1 – CE-7.