Table 1.
Experimental conditions and statistical contrasts. SP is speech production, OBM is one-back matching. Contrast (a) is the main effect of Auditory > Visual conditions. The reverse of this contrast is the main effect of visual input which was not of interest. Contrast (b) is the main effect of speech production compared to one-back matching on exactly the same stimuli. The reverse of this contrast is the main effect of one-back matching which was not of interest. Contrast (c) identified areas where the main effect of speech production (contrast b) was greater than the main effect of auditory input (contrast a) (contrast c = b - a). This is only reported in auditory processing areas (i.e. significant in contrast (a) that also showed an effect of speech production (i.e. significant in contrast (b)), so controlling for all other variables. (c2) is the reverse of contrast (c) and identified areas where the main effect of auditory input (contrast a) was greater than the main effect of speech production (contrast b). Contrast (d) identified the main effect of semantic content (Sem) by comparing pictures, sounds and names of objects to the other conditions. We also tested the reverse of this contrast, (d2). Contrast (e) identified the main effect of sublexical phonological cues to speech production (Phon) by comparing words and pseudowords to all other conditions. We also tested the reverse of this contrast, (e2). Contrast (f) identified whether the effect of words/pseudowords (phonological inputs) was greater in the written domain (orthographic) compared with the auditory domain. The reverse of this contrast (phonological content in the auditory > visual domain) tests for activation related to auditory speech sounds.
| Conditions |
Statistical contrasts |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| a |
b |
c |
c2 |
d |
d2 |
e |
e2 |
f |
|||
| Task | Input | Stimulus | Aud | SP | SP-Aud | Sem | Phon | Orth | |||
| SP | Visual | Pictures of objects | −1 | 1 | 2 | −2 | 1 | −1 | −1 | 1 | −1 |
| Words | −1 | 1 | 2 | −2 | 1 | −1 | 1 | −1 | 1 | ||
| Pseudowords | −1 | 1 | 2 | −2 | −1 | 1 | 1 | −1 | 1 | ||
| Coloured non-objects | −1 | 1 | 2 | −2 | −1 | 1 | −1 | 1 | −1 | ||
| Auditory | Sounds of objects | 1 | 1 | 0 | 0 | 1 | −1 | −1 | 1 | 1 | |
| Words | 1 | 1 | 0 | 0 | 1 | −1 | 1 | −1 | −1 | ||
| Pseudowords | 1 | 1 | 0 | 0 | −1 | 1 | 1 | −1 | −1 | ||
| Baseline (Humming) | 1 | 1 | 0 | 0 | −1 | 1 | −1 | 1 | 1 | ||
| OBM | Visual | Pictures of objects | −1 | −1 | 0 | 0 | 1 | −1 | −1 | 1 | −1 |
| Words | −1 | −1 | 0 | 0 | 1 | −1 | 1 | −1 | 1 | ||
| Pseudowords | −1 | −1 | 0 | 0 | −1 | 1 | 1 | −1 | 1 | ||
| Coloured non-objects | −1 | −1 | 0 | 0 | −1 | 1 | −1 | 1 | −1 | ||
| Auditory | Sounds of objects | 1 | −1 | −2 | 2 | 1 | −1 | −1 | 1 | 1 | |
| Words | 1 | −1 | −2 | 2 | 1 | −1 | 1 | −1 | −1 | ||
| Pseudowords | 1 | −1 | −2 | 2 | −1 | 1 | 1 | −1 | −1 | ||
| Baseline (Humming) | 1 | −1 | −2 | 2 | −1 | 1 | −1 | 1 | 1 | ||