Tactile sensitivity in typical and atypical development

Abstract

The tactile sense is fundamental for typical development yet has been largely under studied in comparison to other sensory modalities of vision and audition. Some individuals exhibit unusual behavioural responses to sensory stimulation that would normally not be considered to be noxious. There has been an increase in research exploring these unusual sensory abnormalities over the last 10 years. Previously only reported anecdotally, some individuals are aversive to or withdraw from tactile stimulation. Referred to as tactile This thesis aims to explore tactile sensitivity in typically developing individuals and those individuals most likely to have sensory abnormalities, specifically Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD). Chapter one summarises literature on the importance of touch for development and introduces theories of tactile defensiveness. A questionnaire study explores texture preferences and aversions in Chapter two. Since little is known about texture preference in either typically developing children or those with ASD / ADHD the purpose of the questionnaire was to create a baseline of texture preference. A further study explored preference for texture complexity. Contrary to expectation, no differences in texture preference were found between comparison groups. Since no differences in texture preference were found, it was predicted that perhaps differences in unusual tactile response may be due to heightened sensitivity to texture for those individuals with sensory abnormalities. Chapter three investigated tactile sensitivity to fine texture and predicted that individuals with ASD would be more accurate at texture discrimination than typically developing individuals. No group difference was found in texture discrimination. In Chapter four, cross-modal matching of texture was explored. It was proposed that unusual tactile response observed in individuals with ASD may be due to difficulty matching visual and tactual information. In a series of studies, results found that individuals with ASD were impaired at matching texture information cross-modally. The inability to accurately match visual-tactual texture information may contribute to the negative tactile reactions observed in individuals with ASD and may provide insight into a possible contributing factor to tactile sensitivity in atypical development.defensiveness, this unusual tactile response has been explored primarily with the use of questionnaires. Literature reports both over-responsivity (hyper) and under-responsivity (hypo) to tactile stimulation in atypical development, for example exhibiting negative response to social touch or an extreme fascination with certain tactile stimulation. Tactile defensiveness affects many facets of behaviour, including motor development, learning and social interaction. In some extreme cases, individuals with tactile defensiveness will avoid human contact. To date, there is no systematic research examining tactile sensitivity in typical or atypical development despite these negative consequences for many aspects of development.