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Available online at www.sciencedirect.com
ScienceDirect Journal homepage: www.elsevier.com/locate/cortex
Letter to the Editor
Stimulus-parity synaesthesia (1893, 2014): Introducing a ‘forgotten’ subtype Rebekah C. White a,c,* and Anna Plassart b,c a
Department of Experimental Psychology, University of Oxford, United Kingdom Faculty of History, University of Oxford, United Kingdom c Christ Church, University of Oxford, United Kingdom b
article info Article history: Received 16 July 2014 Reviewed 13 August 2014 Revised 9 September 2014 Accepted 15 September 2014 Published online 27 December 2014
When an individual with synaesthesia listens to a piece of music, she may see the notes as a kaleidoscope of colours dancing before her eyes, feel each note brushing against her skin, and swirl the notes around her mouth appreciating the rich flavours (Cytowic & Eagleman, 2011). The term synaesthesia e from syn- (joining) and -aesthesia (sensation) e conjures images of cross-sensory experience, but many subtypes involve higher-order cognitive constructs as the inducing stimulus or concurrent experience (Simner, 2012). For example, in sequence-space synaesthesia, ordinal sequences (e.g., letters, months) are perceived as having an idiosyncratic two- or three-dimensional structure (Eagleman, 2009) in the mind's eye or the space around the body (Jonas, Taylor, Hutton, Weiss, & Ward, 2011); and in ordinal linguistic personification (OLP),1 letters and numbers are experienced as
having animate properties, such as gender and personality (Calkins, 1893; 1895; Simner & Holenstein, 2007). As of September 2014, at least 63 subtypes of synaesthesia have been identified (Day, 2014). Here we present a new subtype, in which a range of stimuli involuntarily elicit strong feelings of oddness or evenness. In our review of the contemporary literature, we did not find any references to this phenomenon, which we have tentatively termed “stimulusodore parity synaesthesia”. However, on examining The Flournoy's 1893 book Des phenomenes de synopsie [“Of synoptic phenomena”] e which details findings from a questionnaire completed by 371 synaesthetes e we discovered that he also encountered individuals who experienced many stimuli (e.g., weekdays, faces, types of food, “everything in the world”, p. 223) as odd or even. In a chapter dedicated to personification phenomena, Flournoy presented a footnote in which he noted that for such individuals: … some weekdays appear as even, and the others as odd, even though opinions disagree about the specific attribution …. This is not about the oddness or evenness being attributed to days according to their number of appearance in the week, but about perceived qualities. What I wrote earlier about numbers also applies to oddness and evenness: there is, in these apparently abstract notions, something perceptual. It is too vague and indefinable to be noticed by most people, but some perceive it very clearly not only in the days of the week, but in everything in the world, even in faces and… vegetables. Thus a subject who displays many phenomena of this kind, used to see all the faces he encountered as odd or even, according to the length of the nose,
* Corresponding author. Department of Experimental Psychology, University of Oxford, United Kingdom. E-mail addresses: [email protected]
(R.C. White), [email protected]
(A. Plassart). 1 € rtner, and Taylor (2011) suggest an alternative nomenclature e sequence-personality synaesthesia. Simner, Ga
http://dx.doi.org/10.1016/j.cortex.2014.09.023 0010-9452/© 2015 Elsevier Ltd. All rights reserved.
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Table 1 e Examples of odd and even stimuli. Synaesthete R
Letters Numbers Weekdays Months Colours
a, b, d, f 1, 9, 11, 14 Tuesday, Thursday January, March black, blue, grey
c, e, g, o 2, 3, 4, 5 Sunday, Monday February, June bronze, gold, red
N all ‘teen’ numbers Tuesday, Thursday January, February black, silver, yellow
A, C, D, E 5 Wednesday, Saturday March, May white, gold, red
Note. R's odd-even associations are strongest for lower-case letters, and M's for upper-case letters.
etc., and still finds that lettuce and rhubarb are even, rice and pasta even, and so on.2 We present two contemporary cases.
R is a 32 year-old right-handed female. She has sequencespace synaesthesia, with numbers, letters, time, weekdays, and months occupying 3-dimensional shapes in the mind's eye and around the body. She reports that some numbers and letters have colours, as do weekdays and months. For as long as R can remember, many stimuli e letters, numbers, weekdays, months, colours, shapes, and words e have elicited very strong feelings of oddness or evenness (for examples, see Table 1). R explains that when she encounters a stimulus, she generally gets a sense of the shape of the stimulus and a feeling of oddness or evenness. This feeling is immediate and, in the case of numbers, R reports that the feeling arises “before I have a chance to work out whether the number is actually odd or even”. R elaborates that numbers with several digits have “more of a shape, which gives a stronger feeling”. R's subjective impression is that her odd-even associations have largely stayed the same throughout her life. M (R's father) is a 62 year-old right-handed male. He has sequence-space synaesthesia for numbers, letters, months, years, time, currency and temperature, with most spatial forms experienced in the mind's eye. Weekdays have colours, and some sounds and tastes have a form. M explains that when he encounters certain stimuli e letters, numbers, weekdays, months, colours, cars, words, buildings, and people e “I get a ‘feeling’ of odd or even”. However, the intrinsic value of numbers “gets in the way of my odd/even feelings”, with the exception of 5 which is experienced as even, and ‘teen’ numbers which are experienced as odd. Although M's odd-even feelings were strongest when he was very young, his subjective impression is that most odd-even associations have stayed the same. An objective marker of consistency was obtained by assessing R and M at two time points, separated by 3 months. A stimulus list was generated by the experimenters. The list comprised 78 stimuli: letters (26), numbers (20), weekdays (7), months (12), and colours (13). R and M were asked to write ‘odd’ or ‘even’ beside each item. However, on viewing the list, 2 This passage represents the only discussion of the odd-even phenomenon in the book, and Flournoy does not specify how many individuals he encountered with this type of synaesthesia.
R asked whether it was possible to have the stimuli presented verbally. R explained that her odd/even associations are strongest when she hears a word, and are sometimes affected by the format in which a stimulus is presented; for example, a ‘typically’ even stimulus may elicit an odd feeling if written with a particular font.3 At Time 1, R indicated that 61 stimuli on the list were odd or even, and M indicated that 63 stimuli on the list were odd or even. The Time 2 task was identical, but R and M's lists comprised only stimuli that elicited a response at Time 1. R responded to all 61 stimuli, and 59 responses were identical at the two time points (letters ¼ 20/21; numbers ¼ 16/ 17; weekdays ¼ 6/6; months ¼ 8/8; colours ¼ 9/9), giving an overall consistency of 97%. M left 15 letters blank, explaining that he did not have “strong feelings” for most letters, and had responded to only those letters for which he experienced a compelling odd/even association. M thus provided a response for 48 stimuli at both time points, and 45 responses were identical (letters ¼ 10/11; numbers ¼ 8/8; weekdays ¼ 7/7; months ¼ 11/12; colours ¼ 9/10), giving an overall consistency of 94%.
Two related individuals report that a range of stimuli elicit feelings of oddness and evenness. To the best of our knowledge, this is the first presentation of this phenomenon in the contemporary literature. R admits that she is not sure why she uses the terms odd and even, rather than another contrasting pair e male/female, left/right, ying/yang e it is simply that things “feel odd or even”. Labelling non-numerical stimuli as odd and even may seem incomprehensible to a nonsynaesthete, but R and M cannot imagine thinking about the world in any other way. They have both used odd-even labels for as long as they can remember, without having discussed it with one another.4 3 Some individuals with ordinal linguistic personification report that personality attribution varies depending on contextual factors such as the style, size and font of letters (Amin et al., 2011). 4 Prior to participating in this research, R did not realise that her ‘odd-even’ attributions were unusual. After describing the phenomenon to RCW, she briefly mentioned it to her family members, saying something to the effect “What would you say if I said that Tuesday was odd?” Whereas her mother, sister and brother were bemused and perplexed, R's father indicated that he understood precisely what she meant by this. They did not discuss oddness and evenness in any further detail, until we had collated full case descriptions.
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At the end of the 19th Century, Flournoy (1893) remarked that the attribution of oddness or evenness to weekdays is “even more common” than the attribution of gender to weekdays. The latter phenomenon, a type of OLP, went relatively unexplored in the 20th century (although see Luria, 1968) but has generated research interest in the last 8 years (e.g., Simner & Holenstein, 2007; Simner & Hubbard, 2006; Vijayasree & Rajasekhar, 2013). There are notable parallels between the odd-even phenomenon and OLP, in which (a) stimuli are frequently assigned to one of two conceptual categories (i.e., male/female), and (b) triggering stimuli include letters, numbers, weekdays and months (Simner & Holenstein, 2007).5 However, it is not the case that R and M use the labels odd and even to denote particular personality types. R says that odd things give a dark feeling, whereas even things give a warm and light feeling, and M says that odd things are intricate, whereas even things are full and wellrounded, but neither R nor M experience inanimate stimuli as human-like. As an interesting aside, M does say that a person's personality and appearance determine whether he or she is perceived as odd or even; thus a man may elicit an even feeling based on the man's extroversion. But this does not mean that the colour gold, which M also experiences as even is ascribed an extroverted personality. For M, personality can be an inducer, but it is not a concurrent! Simner and Holenstein (2007) have argued that OLP constitutes a subtype of synaesthesia, and we believe the same can be said for the odd-even phenomenon. Early onset is a characteristic of synaesthesia, and our cases report that they have experienced stimuli as odd or even for as long as they can remember. Synaesthetic associations tend to be consistent across time, and our cases demonstrate highly consistent odd-even attributions. Individuals with one form of synaesthesia are likely to have another (Simner, 2012), and our cases report multiple other subtypes. Concurrent experiences in synaesthesia are perceived as involuntary, and our cases report that stimuli elicit an immediate feeling of oddness or evenness that, in the case of numbers, can interfere with actual odd-even judgements. It will be important to verify this subjective impression of immediacy in empirical work. Many questions remain. How do prevalence rates for stimulus-parity synaesthesia compare with OLP? Does it cooccur with particular subtypes of synaesthesia? Is there a connection with personality traits, memory abilities, or other personal qualities, as has been documented for some other subtypes of synaesthesia? We hope that this Letter will rekindle interest in this phenomenon, inspiring further investigations.
Ordered linguistic sequences such as these are known to trigger 82% of synaesthetic experiences (Simner et al., 2006).
Acknowledgements We wish to thank R and M for participating in this study, and Dr Rob McIntosh and an anonymous Reviewer for exceptionally helpful comments on the manuscript.
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