The Neuroscientist http://nro.sagepub.com/ Exceptional Abilities in the Spatial Representation of Numbers and Time: Insights from Synesthesia Roi Cohen Kadosh, Limor Gertner and Devin Blair Terhune Neuroscientist 2012 18: 208 originally published online 12 May 2011 DOI: 10.1177/1073858411402835 The online version of this article can be found at: http://nro.sagepub.com/content/18/3/208 Published by: http://www.sagepublications.com Additional services and information for The Neuroscientist can be found at: Email Alerts: http://nro.sagepub.com/cgi/alerts Subscriptions: http://nro.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav >> Version of Record - May 22, 2012 OnlineFirst Version of Record - May 12, 2011 What is This? Downloaded from nro.sagepub.com at Oxford University Libraries on October 31, 2013 NRO18310.1177/107385841 4028351402835Kadosh et al.The Neuroscientist Hypothesis The Neuroscientist 18(3) 208 –215 Exceptional Abilities in the Spatial © The Author(s) 2012 Reprints and permission: http://www. sagepub.com/journalsPermissions.nav Representation of Numbers and DOI: 10.1177/1073858411402835 Time: Insights from Synesthesia http://nro.sagepub.com Roi Cohen Kadosh1, Limor Gertner2, and Devin Blair Terhune3 Abstract In the study of basic and high-level cognitive functions, neuroscientists, psychologists, and philosophers have tended to focus on normal psychological processes and on deficits in these processes, whereas the study of exceptional abilities has been largely neglected. Here the authors emphasize the value of researching exceptional abilities. They make the case that studies of exceptional representations, such as of time, number, and space in synesthesia, can provide us with insights regarding the nature of the neurocognitive mechanisms of these dimensions, as well as their developmental, evolutionary, and cultural origins. Keywords synesthesia, exceptional abilities, development, evolution, neuronal specialization, cognitive cost Studies on psychological processes such as perception, conclude by discussing why this exceptional binding occurs emotion, cognition, and action have provided considerable and suggest plausible developmental and evolutionary understanding of these faculties in the average human, origins at the brain level. whereas neuropsychological research has focused on acq- uired and congenital deficits in humans and lesion studies in animals. In contrast, relatively little attention has been TNS Synesthesia devoted to the mechanisms underlying the exceptional Do you see numbers vividly in certain locations in space? exp ression of human abilities, such as superior mathemat- For example, do you see the numbers 1 to 10 running from ical or language abilities. In this article, we focus on such the right to the left and then exhibiting an upward 30° enhanced abilities. We attempt to demonstrate how the trajectory? Do you disagree with this description because study of enhanced abilities can advance our knowledge you see numbers in another shape? Perhaps you can see about psychological processes and brain function and org- instead numbers, different units of time, such as hours, anization, using the examples of time, number, and space. days of the week, months, or even years in a specific spatial By providing a window onto a wider spectrum of human location (Figure 1)? If yes, you are probably one out of abilities, such research will allow us to examine questions approximately five people who possesses a distinct condi- pertaining to cognitive and neural processes in a more tion in which numerical sequences are represented as spa- comprehensive fashion that moves away from a categori- tial arrays (Mann and others 2009; Sagiv and others 2006), cal design (impaired abilities in function X normal abil- ities in function X) toward a parametric modulation (low 1 Department of Experimental Psychology and the Centre for abilities in function X average abilities in function X Functional Magnetic Resonance Imaging of the Brain, high abilities in function X) and, in turn, provide a finer University of Oxford, Oxford, England understanding and characterization of human abilities. 2Department of Psychology and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel We start by introducing the phenomena of explicit vis- 3 ualization of time and/or number in space (henceforth, Department of Experimental Psychology, University of Oxford, Oxford, England TNS synesthesia), a neurological condition with a genetic basis that leads to an overbinding of different features Corresponding Author: (Asher and others 2009). This is followed by an overview Roi Cohen Kadosh, Department of Experimental Psychology, University of Oxford, Tinbergen Building, South Parks Road, of its cognitive and neural mechanisms, together with Oxford, OX1 3UD the gains and costs of such exceptional experiences. We Email: [email protected] Cohen Kadosh et al. 209 Box 1. (continued) idiosyncrasy of synesthesia (but see Cohen Kadosh, Henik, and Walsh 2007; Rich and others 2005; Simner and others 2005; Ward and others 2006), stimulated little scientific interest. With the recent adoption of behavioral research methods together with rigorous neuroscientific techni ques, synesthesia research has gained a greater empirical footing and undergone a revival in the past 15 years. Nevertheless, the study of synesthesia has been biased toward specific types of synesthesia, such as sound-color or grapheme-color synesthesia (Hochel and Milan 2008; Hubbard and Ramachandran 2005; Rich and Mattingley 2002; Figure 1. An example of three-dimensional representations Robertson 2003; Ward and Mattingley 2006), a trend of time units (months, days of the week) and numbers in that has been somewhat reversed in the recent years with mental space, as depicted by different time, number, and space a multitude of studies published on TNS synesthesia (TNS) synesthetes. Modified from Cohen Kadosh and Gertner, (e.g., Eagleman 2009; Gertner and others 2009; Hubbard 2011, with permission from Elsevier. 2009; Mann and others 2009; Piazza and others 2006; Price 2009; Price and Mentzoni 2008; Sagiv and others an ability that is implicit in the average population (Bueti 2006; Simner 2009; Simner and others 2009; Smilek and Walsh 2009; Cantlon and others 2009; Walsh 2003). and others 2007; Tang and others 2008; for an excep- This phenomenon of overbinding different features is tion, see Seron and others 1992). termed synesthesia (Box 1). Recently, a number of studies have investigated TNS synesthesia (e.g., Eagleman 2009; Cognitive Processes of Time, Gertner and others 2009; Hubbard 2009; Mann and oth- Number, and Space ers 2009; Piazza and others 2006; Price 2009; Price and Mentzoni 2008; Sagiv and others 2006; Simner 2009; Can synesthesia inform cognitive processes and neural Simner and others 2009; Smilek and others 2007; Tang mechanisms in nonsynesthetes? Many studies have ans- and others 2008). These studies provide important insights wered this question positively by showing that the synes- into the ways that time, number, and space are represented thetic experience is quantitatively, rather than quali tatively, by TNS synesthetes and nonsynesthetes. different from that of nonsynesthetes. That is, the processes underlying synesthesia appear to be present in all people Box 1. Synesthesia to varying extents, albeit at a different level of awareness (Cohen Kadosh and Henik 2007), but may result from Synesthesia is not restricted to TNS and is present for a different factors in synesthetes such as the magnitude of wide variety of psychological processes (e.g., listening to cortical inhibition and/or white matter brain connectivity music, seeing a grapheme) that automatically trigger (Bargary and Mitchell 2008; Cohen Kadosh and Walsh ancillary, exceptional experiences (e.g., color, taste, 2008; Grossenbacher and Lovelace 2001; Rouw and Scholte smells, pain) in the absence of any direct stimulation 2007; Weiss and Fink 2009). pertaining to the secondary experience (Cohen Kadosh For example, there is a striking resemblance between and Henik 2007; Cytowic and Eagleman 2009; Hochel the explicit representation of number and space in TNS and Milan 2008; Hubbard and Ramachandran 2005; synesthetes and their implicit representation in nonsynes- Rich and Mattingley 2002; Robertson 2003; Robertson thetes. Studies from different countries and educational and Sagiv 2004; Ward and Mattingley 2006). For exam- systems have shown that between 62% and 66% of TNS ple, for some people who see digits in colors (termed synesthetes report representing small numbers on the digit-color synesthesia), an achromatic 7 will appear in left side and large numbers on the right side (Eagleman a distinct color such as turquoise (Cohen Kadosh, 2009; Sagiv and others 2006; Seron and others 1992). This Cohen Kadosh, and Henik 2007). pre valence is similar to the percentage of nonsynesthetes Reports on TNS synesthesia already had appeared at (65%) who similarly represent numbers implicitly from left the end of the 19th century by scholars such as Galton to right as the numbers increase, as indicated by the spatial- (1880a, 1880b) and Flournoy (1893). These studies numerical association of response codes (SNARC) effect were based on introspection and, together with the (Wood and others 2006). Yet, TNS synesthetes are singled out by their enhanced ability to consistently and automat-