Verbal tones in sustainability assurance statements

Purpose - This paper aims to examine, through the lens of language expectancy theory (LET), how sustainability assurors use optimism and certainty in possible persuasion attempts. The paper also explores a number of explanatory variables that could offer insights into the use of these verbal tones in sustainability assurance reports. Design/methodology/approach - First, the paper relies on DICTION standard normalised optimism and certainty ranges in conjunction with descriptive statistics to analyse how sustainability assurors use optimism and certainty. Second, the paper uses quantile regression with robust standard errors to investigate the association between the measures of verbal tone used in this study and several possible explanatory variables. Findings - Consistent with LET, the study documents that sustainability assurors exercise caution in using both certainty and optimism in persuasion attempts. The paper also finds that possible explanatory variables significantly associated with optimism include praise, assurance level, legal system and report location. However, reference to sustainability management control (SMC), status of assurance providers, praise, legal system and financial performance appear to explain the use of certainty. Research limitations/implications - The paper does not, at this stage, claim causality between the two measures of verbal tone, on the one hand, and the possible explanatory variables explored, on the other hand. It rather reports their possible associations. Furthermore, the study only measures reference to management control system and not reliance on it. Practical implications - The main findings of this study imply that the use of optimism and certainty exhibits likely cautious practice by assurors. Nevertheless, assurors are more likely to use certainty more flexibly and appear more discreet when using optimism. Social implications - The findings of this paper also indicate how societal expectations play an important role in ensuring cautious persuasive behaviour by sustainability assurors in using verbal tones within sustainability assurance statements. This suggests that stakeholders may place reliance on attestations expressed in these statements. Originality/value - The paper represents the first attempt to test LET in sustainability accounting by analysing verbal tones used by sustainability assurance providers. It contributes to the sustainability assurance literature in that it empirically demonstrates how sustainability assurors, as expert communicators, use optimistic tone and verbal certainty in careful persuasion attempts.