A member walks up to you after class. “I’ve hit a plateau,” they say. “What should I add?” More cardio? An extra session? A new supplement? You’ve heard this question a hundred times. What you’ve probably never heard? “What should I take out?”

That’s addition bias at work. Addition bias is the human tendency to solve problems by adding something rather than removing something, even when subtraction would be the simpler, cheaper, or more effective fix. Most people don’t even consider taking things away as a viable option. The instinct is to stack, layer, and bolt on. Strip back? That barely registers as a choice.

The Psychology Behind Addition Bias

  • What it is: Addition bias, also called additive bias or subtractive neglect, is a cognitive blind spot. When solving a problem, most people default to adding components rather than removing them, and crucially they don’t even consciously consider subtraction as an option. It isn’t that people weigh adding against removing and pick adding. Removing never makes the mental shortlist in the first place. That distinction matters because it changes how you fix the bias: the answer is not better decision-making, it’s prompting people to see subtraction as a choice at all.
  • Who found it: The seminal research is Adams, Converse, Hales and Klotz (2021), published in Nature. The collaboration started with Leidy Klotz, a structural engineer at the University of Virginia who had spent years noticing his architecture and engineering students always wanted to add features to designs rather than carve them away. He partnered with three behavioural scientists, Gabrielle Adams, Benjamin Converse and Andrew Hales, to test whether the pattern held outside engineering. It did. The resulting paper pulled decades of scattered hints into one clean, replicable finding, and Klotz later expanded the research into the popular book Subtract (2021).
  • The psychology: Three mechanisms drive the bias. The first is cognitive load. Subtraction is genuinely harder mental work than addition. To subtract well, you have to inventory what’s already there, evaluate each component on its merits, predict what happens when each one is removed, and pick the removal that produces the cleanest result. Addition skips most of those steps. You see a problem, you reach for a solution, you bolt it on. One move, done. The second is search and salience. When you look at a problem, the things you could add tend to be more cognitively available than the things you could remove. Adding draws on imagination, which the brain does eagerly. Subtracting draws on critical evaluation of what already exists, which the brain does reluctantly. The third is social and cultural signalling. Adding demonstrates effort and produces visible output. Subtracting can look like neglect or laziness, even when it’s the smarter move. From school onwards we are rewarded for “showing our working” and for producing more. The cultural defaults all push in one direction.
  • The pivotal study: In the headline experiment, participants were given a Lego structure: a small platform held up by a single corner pillar, with a figurine on top. The pillar was unstable and the platform would topple under load. Participants could either pay 10 cents per brick to add support pillars at the other corners, or remove the single problem pillar for free, after which the platform sat flat on the table and held the figurine without issue. Most participants added, even though removal was both cheaper and faster. Across eight experiments covering Lego structures, grid patterns, written essays, recipes, schedules, organisational charts and travel itineraries, the same pattern held. The most useful finding came from the priming conditions. When researchers gave participants an explicit reminder that they could also remove pieces, performance improved dramatically. People weren’t choosing addition over subtraction. They simply weren’t generating subtraction as an option in the first place. The fix is awareness, not willpower.

How Addition Bias Shows Up in Your Gym

  • In Programming & Class Design: Look at most gym programmes and you’ll see exercise lists that have grown over months and years without anyone questioning whether everything still earns its place. A new movement gets added because it’s trending. A finisher gets bolted on because someone read about it. Pretty soon, your hour-long session is trying to deliver eight different goals. The fix is rarely “add a recovery block.” It’s usually “cut three exercises.” Members training with focused, simpler programmes often progress faster than those grinding through bloated ones.
  • In Marketing & Sales: Your homepage has six call-to-action buttons. Your sales conversation covers eleven membership benefits. Your monthly email contains four offers. Each addition feels like more value. To the prospect it reads as noise. Apple sells one phone with three buttons. Your gym sells fifteen membership tiers with thirty add-ons. Subtraction in marketing is brutal because every removed feature feels like a sacrifice, but cluttered offers convert worse than focused ones every single time.
  • In Personal Training & Coaching: Watch a new coach teach a deadlift. Brace your core. Breathe in. Lats tight. Knees out. Chest up. Eyes forward. Drive through the heels. The cue list keeps growing because adding cues feels like good coaching. The client, meanwhile, has stopped processing anything. One well-chosen cue almost always beats five competent ones. The same applies to programme feedback, exercise selection and goal-setting. The best coaches subtract.
  • In Business Operations & Staff: Retention is dropping, so you add a new class. Sales are slow, so you add a new pricing tier. Members are confused, so you add a new induction process. Your team is overwhelmed, so you add a project manager to coordinate the chaos. None of these solutions starts with “what should we stop doing?” The result is a business that gets steadily more complex, more expensive to run, and harder to deliver consistently. Most gyms don’t have a marketing problem. They have an addition problem.

Real-World Examples from Other Industries

  • In-N-Out Burger: While every other major fast-food chain has expanded its menu year after year, In-N-Out has kept its menu almost identical for over seventy years. Burger, fries, shake. That’s basically it. Competitors have piled on breakfast, salads, plant-based options, limited editions, and entire seasonal ranges. In-N-Out subtracts the temptation to add. The result is faster service, simpler operations, fanatical customer loyalty, and a brand that means one specific thing in customers’ minds. Their resistance to addition bias is their entire competitive advantage.
  • Apple Under Jony Ive: When Jony Ive ran Apple’s design team, he famously approached every product by asking what could be removed rather than what could be added. The original iPod removed buttons. The iPhone removed the keyboard. Later iPhones removed the home button, the headphone jack, and the bezel. Each removal triggered controversy and complaints. Each one stuck because the product was simpler to use afterwards. Apple built a trillion-dollar company on the principle that the best feature is often the absent one.
  • Marie Kondo and the Decluttering Industry: Marie Kondo built a global empire by selling people on the idea of removing things from their lives. Her message ran directly against decades of consumer marketing telling people to add more stuff. The KonMari method became a Netflix series, a bestselling book translated into more than forty languages, and a multi-million-dollar brand. The product she sold wasn’t a thing. It was permission to subtract. Addition bias is so strong that an entire industry now exists just to help people overcome it.

Related Biases & Mental Shortcuts

  • The IKEA Effect: When you’ve personally added something to your gym, your programme, or your business, you tend to overvalue it. That makes subtracting it feel like destroying something you built, even when removal would clearly help.
  • Sunk Cost Fallacy: The more you’ve invested in adding a feature, class, or service, the harder it becomes to remove it. The investment locks you in, even when subtraction is the right call.
  • The Endowment Effect: Once something exists in your business, you feel ownership over it. That ownership inflates its perceived value and makes removal feel like a loss rather than a clean-up.
  • Doubling-back Aversion: Subtracting something you previously added can feel like admitting you were wrong. Doubling-back aversion makes it psychologically easier to keep adding rather than reverse course.

The “BS” Takeaway

The fitness industry has an addition problem. Every year brings new equipment, new methodologies, new supplements, new tech, new certifications, new metrics, and new marketing channels. Coaches keep stacking. Members keep stacking. Gyms keep stacking. The people who win usually aren’t the ones with the most. They’re the ones with the least clutter.

Next time something isn’t working in your business, your programme, or your training, resist the reflex to add. Ask the harder question first. What’s already in there that I could remove? What if the problem isn’t that there’s too little. It’s that there’s too much.

You’re not in the business of giving members more things to do. You’re in the business of helping them get a result. Sometimes that means handing them another exercise. More often, it means taking three away.

The best programmes, the cleanest businesses, and the sharpest brands all share one trait. Someone, somewhere, had the discipline to subtract.

Bibliography & Further Reading