Individuals diagnosed with Parkinson's Disease consecutively recruited at the beginning of rehabilitative treatment at the Istituto Auxologico Italiano, IRCCS, San Giuseppe Hospital (Italy). Concurrent neurological, neurodevelopmental (e.g., autism), motor or psychiatric disorders were exclusion criteria.

Age-matched healthy individuals recruited outside the hospital through personal contacts of the researchers and word-of-mouth.

All participants were asked to complete the Counterfactual Inference Test - CIT (McNamara et al., 2003), a neuropsychological test that measures the ability to produce counterfactual-derived inferences. Moreover, the decision-making ability will be specifically tested through ad-hoc questionnaire (i.e., the Decision-Making Questionnaire). Finally, all participants will be screened with an extensive neuropsychological assessment, particularly on executive functioning.

Score at the Counterfactual inference test (CIT). The questionnaire is a four question forced choice test based on past research regarding factors that enhance counterfactual thinking. For each of the four questions, events experienced by two individuals are presented, and three response options are given. Only one option is the valid: the score is 1. For the not valid options, the score will be 0. Overall, the score range for the questionnaire is from 0 (worse performance) to 4 (best performance).

Score at the Decision-Making Questionnaire. The self-report questionnaire assesses the decision making ability according to 7 questions, with a 5-item Likert's scale. The overall score (i.e., the sum of the scores at all questions) can range from 7 (worse decision making strategy) to 35 (best decision making strategy).