Is "Jumpiness" in Evidence Accumulation a Personality Trait? Cross-task Correlations and Retest Reliability of the Parameters of the Lévy Flight Model

The Lévy flight model of decision making has been suggested as a modification of the well-known diffusion model. Due to the assumption of a more heavy-tailed, non-normal noise distribution of the information accumulation process, the new model is able to account for fast error responses in two alternative forced choice tasks. Compared to the standard diffusion model, the Lévy flight model contains an additional free parameter, 𝛼, that describes the heaviness in the tails of the noise distribution. Alpha determines the amount of jumps in evidence accumulation. In this paper, we address the crucial question whether stability parameter 𝛼 meets essential preconditions that are necessary for an interpretation as a trait-like measure: We test stability of 𝛼-values across tasks and across time. Study 1 assesses correlations between 𝛼 across a letter-number-discrimination, a lexical decision and a color-discrimination task. In Study 2, data from two sessions – separated by one week – were reanalyzed to calculate retest reliability of 𝛼 in a recognition-memory and a lexical-decision task. Medium to high correlations of 𝛼-values across tasks and acceptable retest reliabilities of 𝛼provide initial evidence for a trait-like measure. Possible psychological interpretations of 𝛼 are discussed.