Enhanced Memory Ability: Insights from Synaesthesia

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Consider the following quote from a synaesthete participant in our studies:"My coloured letters and numbers are for me wonderful memory aids and reminders. Not only are telephone numbers and dates, such as birthdays and anniversaries, made up of beautiful combinations of colours, they can also have shapes.... Units of time are visible to me too; sometimes they are three-dimensional, coloured or textured in appearance... This system helps me to plan my year". Synaesthesia is a remarkable way of perceiving the world. For some people, such as the person quoted above, letters, numbers and words may have colour (grapheme-colour synaesthesia) and sequences, such as years and months, are 'seen' as a three-dimensional figure in space (time-space synaesthesia). We have shown that synaesthesia runs in families and is present from a young age. The experiences are elicited (i.e. triggered by particular stimuli), automatic (i.e. occur involuntarily), and are often reported to have qualities of perceiving. To those who have synaesthesia it feels perfectly normal: that is, it is impossible to imagine what it is like to have, say, colourless numbers. On formal testing, however, synaesthetes have an unusual cognitive profile of strengths and weaknesses. In this research programme we will investigate enhanced memory in synaesthesia.Our general approach is to treat synaesthesia as a 'test case' to address other important research questions. For instance we consider how synaesthesia can inform general theories of memory. Importantly, not all aspects of memory are enhanced in synaesthesia and this can provide insights into how the memory system is structured. Indeed it is not trivially the case that material that elicits 'extra' sensations are better remembered: some material that does not evoke extra sensations (such as abstract figures) are also better remembered by synaesthetes. We suggest that synaesthetes have widespread changes in their perceptual systems (including but not limited to their extra experiences) and that systems supporting perception can also be engaged in memory. This approach makes contact with a much wider contemporary literature on memory including those arguments derived from animal models and patients with amnesia. In principle, studies of superior ability can be just as informative to models of memory as studies of impaired ability, even though the latter approach predominates. Moreover, cognitive psychology as a discipline has historically tended to dismiss rather than embrace individual difference (classifying it as 'noise' in the data). As such, we seek to tackle important questions relating to memory from a novel angle. An understanding of individual differences in memory functioning, derived from our research on synaesthesia, will have significant impact on other areas. For instance, one claim is that enhanced functioning in general may be protective against pathology or cognitive decline in ageing. We will test whether synaesthesia is a protective factor against age-related memory decline. Another claim is that the kind of 'low level' or 'visualising' cognitive style that we hypothesise to give rise to enhanced memory in synaesthesia may support enhanced memory in other special populations (e.g. savant memory abilities such as those sometimes found in autism). Although we do not test this directly in our main proposal, our findings will be relevant to those working in this domain and will be explored in a linked PhD.To tackle these questions we draw on a wide range of methods in cognitive psychology/neuroscience. We use both standard and bespoke tests of memory to explore which aspects of memory are enhanced. We explore how individual differences in perception (in non-synaesthetes) may relate to performance on certain memory tasks. Finally, we explore how the brain supports enhanced memory in synaesthesia using neuroimaging and non-invasive brain stimulation methods