Experiment rationale: - Habits are responses (R) that become independent of their original goals. Therefore, habits are controlled by their antecedent events (S) and not by their consequent outcomes (O). Learning theory establishes that habitual responses should be, by definition, insensitive to sudden changes in the value of the O. (Dickinson, 1985 [URL: http://rstb.royalsocietypublishing.org/content/308/1135/67]. - Although there is wide agreement about the relevance of studying habit learning and control, there are only a few studies actually trying to show evidence of habitual learning in humans. Notably, recently these results have received strong critics (see De Houwer et al, 2018 [URL: http://psycnet.apa.org/record/2017-38145-001]; de Wit et al.[preprint: https://osf.io/a62x5/]) - This series will investigate response habitualization in human reinforcement learning trying to overcome these critics. - Specificaly, we will investigate the effect of amount of training and outcome value over the formation of S-R habits. Habits will be assessed in outcome devaluation tests. - Dependent variables will be the number of persistent responses to devalued outcomes and, for the first time, response times for goal-directed reversal responses. - In addition, we'll also manipulate response time pressure: In the first of experiment half of the participants will have little pressure (4 seconds), the other half will have high pressure (just 0.5 seconds).