Why do people fail to follow through on their own intentions? Often, the answer isn't motivation, knowledge, or willpower. It's friction—the small efforts, delays, and obstacles that stand between a decision and its execution.

Behavioral research has consistently shown that even trivial barriers produce outsized effects on behavior. Adding a single step to a process can cut participation by half. Removing one can double it. This sensitivity to effort is both a vulnerability and an opportunity.

For intervention designers, friction is among the most reliable and cost-effective levers available. Understanding when to add it, when to remove it, and when to leave it alone separates effective programs from well-meaning failures.

Humans are cognitive misers. We conserve mental energy by defaulting to the path of least resistance. This isn't laziness—it's efficient resource allocation in a world of competing demands.

The implication is that behavior follows the contours of effort. Economists call this a transaction cost. Psychologists call it response cost. Whatever the label, the pattern is consistent: as effort increases, behavior decreases, often in nonlinear ways.

Classic experiments demonstrate this. In one study, moving a candy dish from desk to drawer—a difference of six feet—reduced consumption by 50%. In another, requiring employees to actively enroll in retirement plans dropped participation from over 80% to under 50%, compared to automatic enrollment with an opt-out.

The mechanism operates through multiple channels. Friction increases the time required, which competes with other activities. It increases cognitive load, making the behavior harder to remember and execute. And it disrupts momentum—each interruption is an opportunity to reconsider, abandon, or forget. These effects compound. What seems like a negligible barrier becomes a behavioral wall.

Takeaway

Small barriers don't just slow behavior—they often stop it entirely, because effort costs are psychologically amplified beyond their objective size.

If friction suppresses behavior, then introducing it strategically can reduce harmful actions without prohibition or punishment. This is the logic behind cooling-off periods, warning labels, and multi-step verification.

Consider suicide prevention. Research on means restriction—making lethal methods slightly harder to access—shows remarkable effects. When the UK replaced coal gas with less toxic natural gas, suicide rates dropped by a third and stayed down. The additional effort of finding alternative methods was enough to save lives.

Similar principles apply to impulsive purchases. Studies on online shopping find that adding a brief delay before checkout—even 24 hours—reduces spending without reducing satisfaction with eventual purchases. The friction doesn't prevent buying; it filters out regretted decisions.

Effective friction additions share common features. They're targeted—affecting impulsive or harmful behavior more than deliberate choices. They're proportionate—enough to trigger reconsideration without creating resentment. And they're transparent—people accept friction better when they understand its purpose. Adding steps randomly or excessively backfires, breeding frustration and workarounds.

Takeaway

Strategic friction acts as a filter, not a wall—it disrupts impulsive mistakes while letting considered decisions pass through.

The default intervention in behavioral design is to simplify—fewer steps, shorter forms, faster processes. This works beautifully when the target behavior is unambiguously beneficial. But frictionless design has a shadow side.

Removing barriers can enable impulsive errors. One-click purchasing and instant credit approvals have fueled debt crises. Frictionless sharing on social media accelerates misinformation. Speed and ease eliminate the pause where judgment operates.

Friction can also serve as a commitment device. Gamblers who voluntarily self-exclude from casinos are using friction against their future selves. Some savings programs build in deliberate withdrawal barriers to protect long-term goals from short-term temptation.

Perhaps most importantly, some friction provides informational value. The effort required to complete a complex form may be the only moment when someone fully processes what they're agreeing to. Medical informed consent processes, though cumbersome, exist precisely because the friction forces engagement with risk information. The intervention question isn't simply 'how do we make this easier?' It's 'what cognitive work does this friction perform, and what happens if we remove it?'

Takeaway

Not all friction is waste—some barriers serve as commitment devices, error-catchers, or attention-forcing mechanisms that protect people from themselves.

Friction is neither inherently good nor bad. It's a design variable—one that intervention researchers can manipulate with unusual precision and effect.

The evidence points toward a nuanced approach: remove friction from beneficial behaviors people struggle to perform, add friction to harmful behaviors people struggle to resist, and preserve friction when the effort itself serves a protective or informational function.

Behavior change programs often focus on motivation, education, and incentives. These matter. But the path-of-least-resistance principle means that small structural changes in effort requirements can outperform elaborate persuasion campaigns. Sometimes the most powerful intervention is simply making the right thing a little easier—or the wrong thing a little harder.