Large, macroeconomic shocks in the past have been shown to influence economic decisions in the present. We study in an experiment with 743 subjects whether small-scale, seemingly negligible, events also affect the formation of risk preferences. In line with a reinforcement learning model, we find that subjects who won a random lottery took significantly more risk in a second lottery almost a year later. The same pattern emerges in another experiment with 136 subjects where the second lottery was played more than three years after the first lottery. So, small-scale, random, events affect the formation of risk preferences significantly.