In the originally published version of this manuscript, descriptive statistics are incorrectly reported on page 5, column 2, paragraph 1 (under the heading ‘Test/retest reliability’): ‘However, there was a strong correlation between mean retest subjective score, M?=?3.1 (SD?=?1.9) and the original subjective score of those taking part in the retest (M?=?3.4, SD?=?1.6)’ Corrected text: ‘However, there was a strong correlation between mean retest subjective score, M?=?1.6 (SD?=?1.0) and the original subjective score of those taking part in the retest (M?=?1.8, SD?=?0.9)’ These details have been corrected only in this corrigendum to preserve the published version of record.