Gaining a deeper understanding of the psychology underpinning significance judgements in environmental impact assessment (EIA)

Significance judgements lie at the heart of EIA and provide the basis and justification for overall decision-making. Although the subjective nature of significance judgements is widely recognized, there has been limited research aimed at gaining a deeper understanding of its implications. This paper builds on the growing tradition of exploring learning from psychology in dealing with challenges in EIA practice, in this case, significance judgements. The aim of this research is therefore, to gain a deeper understanding of the psychology underpinning significance judgements. This is achieved by applying 10 concepts from psychology to the four steps in the ‘significance spectrum model’, namely: decide thresholds, make predictions, judge acceptability and consider mitigation. The results suggest that significance judgements should (with underpinning concepts from psychology provided in parentheses) aim for a limited number of key thresholds (paradox of choice); design thresholds with future gains in mind (loss aversion), reconsider probability scoring (possibility and certainty effect); avoid judgements based on limited information (What You See Is All There Is, WHYSIATI); utilise statistical prediction over expert opinion (expert fallacy); communicate carefully (priming, framing and cognitive ease); and consider personal attitudes and biases (affect heuristic).