The choice between enjoying meals at McDonald’s and a fit physique, between smoking cigarettes and healthy lungs or between scrolling through social media and finishing a dissertation - all these ubiquitous decision tasks require humans to trade off costs and benefits at different points in time and are referred to as intertemporal choices. Economists started investigating these trade-offs as early as in the 18th century, yet focussing on the impact of intertemporal choices on economic prosperity instead of on diet, health or academic achievement. Despite early differentiated considerations, a simple theory of intertemporal choice was introduced and quickly adopted in the first half of the 20th century, namely Discounted Utility theory. At its core lies a model which posits that humans choose the option which maximizes the sum of discounted utility flows associated with that option. The explicit and implicit assumptions of the Discounted Utility model, which was not founded on empirical evidence, were finally subjected to scrutiny by psychologists by means of field studies and experiments in the second half of the 20th century. Numerous behavioral anomalies were discovered, which resulted in the development of alternative models, such as hyperbolic discounting, which have markedly higher descriptive validity. Since then, research on intertemporal choice has flourished and produced many valid accounts for various behavioral phenomena. For instance, more often than typically desired, a so-called impulsive choice is made in favor of a smaller but sooner reward (e.g. a Big Mac), thereby forgoing a larger but delayed reward (e.g. a flat belly). Behavioral economists have proposed a key process underlying this decision: delay discounting, i.e. the tendency to discount future rewards depending on their delay. Delay discounting, often simplistically referred to as impulsivity, has been shown to have both trait- and state-like characteristics; people have a stable, partially genetically determined baseline tendency to discount future rewards that may adapt slightly depending on the decision context. Furthermore, neuroscientists have recently begun to investigate the neural mechanisms underlying delay discounting and currently propose the valuation of rewards, cognitive control and prospection as relevant subprocesses. Another finding of high clinical relevance is that delay discounting is associated with numerous problematic behaviors, which include substance abuse but also behavioral addictions.
In parallel, digital devices, such as smartphones, tablets and laptops/PCs, have permeated societies worldwide. Notably, adults’ and even children’s usage of these technologies is often characterized as excessive or, as some researchers propose, addictive. This has begged the question if there is a link between digital device use and delay discounting, i.e. to what extent may smartphone, tablet and laptop/PC use be considered an impulsive choice? The research within this dissertation has contributed three empirical investigations to this young literature. In study 1, we sought to replicate initial findings of a link between smartphone use and impulsivity using more reliable and nuanced methods. Following recent insights on the neural mechanisms underlying intertemporal choice, we also analyzed the role of reward responsiveness, self-control and consideration of future consequences. We found that students’ actual smartphone use was correlated with delay discounting and that this relationship was driven by social media and gaming applications. Furthermore, neither psychological variable mediated the relationship between use of smartphones and the degree of discounting. Study 2 investigated the link between delay discounting and children’s addictive use of digital devices, i.e. use with negative social, psychological, physical and educational consequences. Associations with children’s self-control as well as academic performance were also analyzed. The results showed that children’s preference for smaller, immediate rewards was related to a greater degree of addictive digital device use, but that this relationship was confounded by children’s ability to control their thoughts, emotions and behavior. Additionally, self-control and screen time predicted children’s most recent grade average. Examining delay discounting in the context of a central aspect of digital device use, namely social media rewards, was the goal of study 3. We found that the magnitude effect of delay discounting, i.e. delay discounting decreases with increasing reward magnitude, also applies to Instagram followers and likes. Moreover, the degrees of discounting of money, followers and likes were correlated, providing further evidence for the trait component of delay discounting. Taken together, this research has demonstrated a significant albeit weak association between digital device use and impulsive choice. The causal direction of this relationship remains unresolved, but self-control seems to promote avoidance of harmful outcomes associated with use of digital devices, particularly in children. The studies have also pointed out the importance of adopting a nuanced view on digital device use in future research, with a particular focus on its reward mechanisms.
