<p>In this paper, I propose an account of behavioral addiction in terms of what I call addictive motivational scaffolds (AMSs). Taking inspiration from recent work concerning psychiatric externalism and addiction, I propose and describe the concept of motivational scaffolding: external structure that enhances, supports, or regulates motivational processes in the mind-brain. I then argue that some motivational scaffolds are likely difference-makers in that they make an activity more addictive. The paper proceeds in three main parts. First, I describe the concept of a motivational scaffold and how it builds on recent literature in 4E cognition/psychiatric externalist accounts of addiction. Using gambling and gaming as paradigm cases of addictive activities, I then identify and empirically justify four addictive motivational scaffolds (AMSs): (1) quantified metrics, (2) reward uncertainty, (3) short time-horizon to reward, and (4) physically salient features. Finally, I apply my account to social media to showcase its philosophical usefulness: analyzing behavioral addiction in terms of AMSs uniquely elucidates the more <i>structural</i> aspects of the addictiveness of social media, which are undertheorized.</p>