Table 1.
Summary of studies that have tried to induce an association between sensory features or dimensions comparable to synaesthesia.
| Study | N | Association (IM: intramodal; CM: crossmodal) | Number of trial (over what time period) | Behavioral/neural effect | Conscious concurrent |
|---|---|---|---|---|---|
| Kelly, 1934 | 18 | Tone-color (CM) | 320–3000 (7 weeks) | No effect | No |
| Howells, 1944 | 8 | Tone-color (CM) | 25,000 (12 h for first 5000) | Stroop-type | In the odd participant |
| Nunn et al., 2002 | 12 | Auditory words-colors (CM) | (<1 day) | No change in V4/V8 neural activity | No |
| Elias et al., 2003 | 1 | Digit-color (IM) | (8 years) | Synaesthetic Stroop effect | No |
| Ernst, 2007 | 12 | Visual luminance-haptic stiffness (CM) | 500 (1 h) | Enhanced multisensory integration | Not assessed |
| Cohen Kadosh et al., 2009 | 4 | Digit-color (IM) | Brief hypnotic suggestion | Impaired digit detection task performance | Yes |
| Meier and Rothen, 2009 | 20 | Grapheme-color (IM) | 10 min/day—3300 trials (7 days) | Synaesthetic Stroop effect | No |
| Rothen et al., 2011 | 20 | Grapheme-color (IM) | Non adaptive, 480 trials for 10 days | Priming task (stronger after adaptive training) | No |
| 20 | Grapheme-color (IM) | Adpative, 248 trials for 10 days | |||
| Kusnir and Thut, 2012 | 28 | Grapheme-color (IM) | 1620 trials | Synaesthetic Stroop effect | No |
| Colizoli et al., 2013a | 15 | Grapheme-color (IM) | 45 min (× 2–3 days) read, 49,000 word book (2–4 weeks) | Synaesthetic Stroop effect | Weak support |
| Rothen et al., 2013 | 1 | Swimming style (pictures)-color (IM) | 9600 trials (20 days) | Synaesthetic Stroop effect (no psychophysiological conditioning) | No |
N = Number of participants taking part in study.