Superior Encoding Enhances Recall in Color-Graphemic Synesthesia

Abstract

Synesthesia is a phenomenon in which particular stimuli, such as letters or sound, generate a secondary sensory experience in particular individuals. Reports of enhanced memory in synesthetes raise the question of its cognitive and neurological substrates. Enhanced memory in synesthetes could arise from the explicit or implicit use of a synesthetic cue to aid memory, from changes unique to the synesthete brain, or from both, depending on the task. To assess this question, we tested nine color-graphemic synesthetes using standardized neuropsychological measures that should not trigger color-graphemic synesthesia (visuo-spatial tests) and measures that should trigger color-graphemic synesthesia (verbal tasks). We found a synesthetic advantage on both types of tests, primarily in the initial encoding of information. The pattern of results adds to existing evidence of advantages in synesthetic memory, as well as provides novel evidence that synesthetes may have enhanced encoding rather than superior recall. Synesthetes learn more initially, rather than forgetting less over time.

Are synesthetes exceptional beyond their synesthetic associations? A systematic comparison of creativity, personality, cognition, and mental imagery in synesthetes and controls

“…Follow‐up analyses on the divergent thinking subfactors, as well as specific cognitive subtests (those previously examined in the literature) for the current study and previous studies (Gross et al ., 2011; Rothen & Meier, 2010b), can be found in Supporting Information. Follow‐up analyses on the three WAIS‐III VCI subtests showed that synesthetes scored higher than controls at a large effect size level for information and a medium effect size level for vocabulary (with possible effects ranging from negligible to large).…”

“…(2013). Our cognitive results showed no association between synesthesia and a working memory index and, consistent with previous literature (Gross et al ., 2011; Rothen & Meier, 2009, 2010b), a subtest level examination revealed no group differences in memory for digits (see Supporting Information). This is corroborated by anecdotal reports from grapheme‐colour synesthetes in our study, many of whom said the numbers were read too quickly (one digit per second) to attend to the synesthetic colour.…”

“…Synesthetes showed a small advantage for associative learning; however, the CIs were too large to be meaningful, likely because fewer participants completed this test. Previous studies have found enhanced memory for word pairs in synesthetes (Gross et al ., 2011; Rothen & Meier, 2010b). This contrast from the null findings for digit span tasks may thus be due to the associative nature of the word‐pair task.…”

New insights into mechanisms of enhanced synaesthetic memory: Benefits are synaesthesia-type-specific

“…Rothen and Meier [17] for instance found that grapheme-colour synaesthetes outperformed their control participants in inducer- and concurrent-related as well as synaesthesia-unrelated tasks of the Wechsler Memory Scale. Gross, Neargarder, Caldwell-Harris and Cronin-Golomb[24] on the other hand found an advantage for grapheme-colour synaesthetes only for a part of the inducer-related verbal and synaesthesia-unrelated tasks. These results rather support a general benefit but indicate that a benefit may only occur under certain circumstances.…”

Correcting misconceptions about synaesthesia

“…Humphrey cites a case study describing extraordinary mnemonic abilities in a synaesthete (Smilek, Dixon, Cudahy, & Merikle, 2002), but such individuals are not representative of synaesthetes and seem to have developed their abilities through mechanisms independent of their synaesthesia, such as savantism (Bor, Billington, & Baron-Cohen, 2007). Indeed, group studies, such as the two cited by Humphrey (Gross, Neargarder, Caldwell-Harris, & Cronin-Golomb, 2011;Yaro & Ward, 2007), have revealed that synaesthetes' mnemonic advantage over nonsynaesthetes is statistically robust, but by no means does it reach a level that would sufficiently support Ayumu's performance (Rothen et al, 2012). The cumulative evidence strongly indicates that synaesthesia is not responsible for Ayumu's mnemonic abilities.…”