A hallmark of human behavior is the ability to choose from a set of available actions. According to one theory humans execute the task with the highest priority at each decision point Barabasi (2005); Vazquez et al. (2006). The easy access to smartphones forces us to decide between using the phone or performing some other activity that does not involve the phone. Here we show that the priority placed on the phone shapes the temporal dynamics of the behaviour across multiple time scales and we estimate the perceived importance of touchscreen actions in 84 individuals. Heavy-tailed power- law distribution of inter-event times emerged from repeating a simple decision process that decided between smartphone actions and all other actions. The shape of this distribution was determined by the allocated priority of smartphone actions such that the higher the priority on the smartphone over any other actions the fewer the longer gaps across multiple time scales. Quantification of real touchscreen activities showed a heavy-tailed power law distribution of inter-event times ranging from a second to several hours. Over the sampled population, the mean power-law exponent is 1.82 (+/-0.12) and we estimate that 4.8% of the population consider touchscreen tasks to be more important than any other activity.