Daily life confronts us with information across multiple senses in parallel and we must somehow unite these sensations into a coherent interpretation of the world. The MULTISENSE project is examining how the human brain comes to develop this complex ability, and how certain genetically ‘pre-marked’ brains can come to experience multisensory integration in remarkable ways.

Implicit associations across the senses can have a profound and sometimes surprising effect on our experiences. In eating, for example, the subjective taste of food is significantly altered simply by changing its colour, its shape, or even its name. People with the neurological condition synaesthesia have cross-sensory interactions to an extreme degree: synaesthetes might experience tastes as colourful moving shapes in the visual field, perceive sounds as odours or flavours, or feel colours as tactile sensations against the skin. These unusual sensations have been traced to structural and functional differences in the brains of synaesthetes. Although relatively rare, synaesthesia can give profound insights into normal sensation because all people experience crossed sensations to an implicit degree, and often in ways that mimic synaesthetes. For example, rougher textures tend to be ‘seen’ as darker colours by synaesthetes, but are also paired to darker colours by nonsynaesthetes in sensory association tasks. In this ambitious proposal I will examine the lifespan development of multisensory integration in both synaesthetes and nonsynaesthetes, considering changes that occur throughout childhood, non-elderly adulthood, and older age. How do we develop a sense of unity in a multisensory world? How does this emerge in synaesthetes?  Are they predisposed from birth to map across modalities in specific ways? Do multisensory abilities decline in elderly synaesthetes? How might this inform us about multisensory decline in all people? By addressing these issues, our focus converges on one over-arching question: how does multisensory processing vary, both over time and across individuals (i.e., with and without synaesthesia)?

The MULTISENSE project is a 4-year reserarch project unfolding across four inter-related Work Programmes, in which we will develop a state-of-the-art assessment tool to identify child synaesthetes, and use behavioural tests and experimental techniques to evaluate multisensory functions in synaesthetes and nonsynaesthetes across the lifespan. Our questions stand at the frontier of scientific understanding about synaesthesia and our findings and tools will be fed back to both researchers and educational policy makers, and will frame this field of research for current and future academics.