Table 3.

Prevalence comparisons.

^aSimner and Holenstein, 2007: 78 out of 219 individuals initially reported “some type of OLP and/or grapheme-color synesthesia.” From this group, 21 (9.6%) scored higher than controls (2–3 week retest) 5 weeks later and 10 (4.6%) continued to score higher 1 year later. The strict estimates are derived from these 10 individuals: 2 with OLP, 7 with grapheme-color, and 1 with both.

^bSimner et al., 2006: For comparability with the current study, the proportion of individuals with letter- and/or number-color associations are reported from Simner et al.'s data; therefore this figure is slightly different than the 1.4% typically cited from the university study, referring to individuals with both letter- and number-color associations.

^cSeron et al., 1992: 194 individuals were recruited systematically to take a brief questionnaire. From this group, 27 individuals gave a positive response regarding “some particular number representation;” no breakdown was provided for group composition from the three measured types of associations: sequence-space, number-color/form, and simple analogical representations (“the quantity was directly represented by patterns of dots or other things such as alignment of apples, parts of a bar of chocolate, etc.”). An additional non-systematic, informal inquiry yielded 22 more positive responses. From the mixed group of 49 individuals, 26 agreed to answer a more detailed questionnaire; however, it is unknown how many of these verified associations came from the systematically-recruited group. The sequence-space prevalence is therefore less than or equal to 27/194. It should be noted that sequence-space composed 74% of positive responses from the detailed questionnaire and 68% of positive responses from the brief questionnaire. If the frequency found from the detailed questionnaire is accurate, one might speculate the sequence-space prevalence to be ~10% (0.74 × 13.9%).