Voters rating politicians’ personality: Evaluative biases and assumed similarity on honesty-humility and openness to experience

The recent rise in controversial politicians has garnered substantial interest in the assessment of their personality. Observer ratings of politicians’ personality, however, may suffer from evaluative and value-related biases. Evaluative biases are likely to differentially affect personality ratings of preferred and non-preferred politicians, whereas value-related biases are likely to affect ratings of honesty-humility and openness to experience of preferred politicians in line with the self-based heuristic or assumed similarity effect. In a stratified sample (final N = 203) of the Dutch population, respondents/voters provided self-ratings and observer ratings of the political leaders of the seven largest political parties on the HEXACO Simplified Personality Inventory (HEXACO-SPI). Findings showed evaluative biases on honesty-humility, extraversion, conscientiousness, and openness to experience. Furthermore, observer ratings of politicians were generally lower than self-ratings on honesty-humility and higher on extraversion, suggesting high perceived politicians’ narcissism. Findings on the value-related bias showed that assumed similarity was higher for honesty-humility and openness to experience among politicians of a preferred party than among politicians of non-preferred parties. Additionally, assumed similarity effects were also present for emotionality among preferred politicians and for extraversion and conscientiousness among both preferred and non-preferred politicians, suggesting a self-based prototypicality effect.