The World Happiness Report ranks nations based on their relative happiness and has considered some of the factors that may explain happiness differences between nations, such as trust between people (Martela et al., 2020). In addition to being a key factor affecting happiness, trust is also directly influenced by communication, with open communication promoting higher levels of trust (Ruppel & Harrington, 2000). Cross-linguistic research has also demonstrated that language affects cognitive processes (e.g., memory, perception; Boroditsky, 2001; Kirjavainen et al., 2020), and mental states (e.g., depression; Rude et al., 2004) affect language, but little is known about the effect of language on mental states, such as happiness. Specifically, the role that directness in language use (direct e.g., “I can’t join you” vs. indirect e.g., “I’ve already made plans for that day” vs. ambiguous e.g., “I’d love to come but I might be working that day”) plays in happiness is currently under-researched. The impact of directness may also vary in accordance with the valence – whether the response is positive or negative. Establishing this relationship is crucial, particularly in contexts such as the workplace, where happiness predicts an organisation’s performance and success (Walsh et al., 2018), employee co-operation and prosocial behaviour (Layous et al., 2017), higher goal setting (Baron, 1990), perseverance (Sarason et al., 1986), and proactivity (Bachrach & Jex, 2000). Organisations are also prime examples of well-defined social hierarchies, with differing levels of power, status, and social distance, all known to heavily influence the use of language directness (Brown et al., 1987; Linde, 1988). Thus, given the importance of promoting happiness in the workplace along with the prevalence of indirect speech within organisational hierarchies, it is important to establish whether there is a relationship between indirect communication and stress, the inverse correlate of happiness (Schiffrin & Nelson, 2010). Our study will test if language directness (direct vs. indirect vs. ambiguous) and valence (positive vs. negative vs. ambiguous) affect English speakers’ stress levels by measuring participants’ skin conductance (i.e., electrodermal response) whilst they read realistic WhatsApp conversations as they unfold. In each conversation, one interlocutor makes a request, and the other responds with one of five message categories: positive direct, negative direct, positive indirect, negative indirect, or ambiguous. To assess differences related to workplace conversations and organisational hierarchy (e.g., Linde, 1988), these five types of responses will be presented in four relationship contexts (one outside the workplace, three inside the workplace): a friend speaking to a friend, a colleague speaking to a colleague, an employee speaking to a manager, and a manager speaking to an employee. If participants react differently to replies differing in category and/or context, it will create a solid foundation for tapping into the mechanisms through which communication affects happiness in the workplace, as well as help inform interventions towards organisational cultures, shown to heavily influence styles of communication (Ruppel & Harrington, 2000). More generally, it will also inform the field of language and cognition as to whether language impacts mental states such as happiness. References Bachrach, D. G., & Jex, S. M. (2000). 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