Your brain can't process everything at once, so it filters ruthlessly. Users only notice what they're looking for — or what is designed to demand their attention. Everything else gets tuned out.
In 1999, psychologists Christopher Chabris and Daniel Simons ran a study that became one of the most famous in cognitive science. They asked participants to watch a video of people passing a basketball and count the number of passes. Midway through, a person in a gorilla suit walked through the scene, stopped, thumped their chest, and walked off. About half of all participants never saw the gorilla.
They weren't distracted. They were focused — just focused on the wrong thing. Because their attention was locked on counting passes, the gorilla didn't register at all. This is selective attention: the mind processes only a fraction of what the eyes see, filtering everything else out in order to stay focused on the current task.
In interface design, this plays out constantly. A user looking for the checkout button won't notice the promotional banner at the top of the page. A user reading a form won't notice a small notice buried in the footer. A user focused on filling in their email address won't notice an error message that appeared elsewhere on the screen. Selective attention doesn't mean users are careless. It means they're human.
“We experience far less of our visual world than we think we do. We believe we see everything, but we're actually only ever seeing a small part of it.”
— Christopher Chabris & Daniel Simons, The Invisible Gorilla, 2010
Here's one of the most common selective attention failures in form design. A user fills in a long form and hits submit. There's an error. The error message appears — but it appears at the top of the page, while the user's attention is focused at the bottom where they just clicked the button. They see no feedback, assume nothing happened, and click again. Or they give up.
The fix is simple: put the error message where the attention is. Inline errors, right below the field that needs fixing, work because they appear inside the user's active focus zone. A general error banner at the top of the page fails because it's outside it.
The error banner is at the top. The user just clicked “Create account” at the bottom. Their eyes are down there — not up where the error appeared.
Errors appear directly below the fields that need fixing — inside the user's active focus zone. No need to scroll or look away.
This is selective attention exploited as a dark pattern. A user at checkout has one thing on their mind: completing the purchase. Their attention is locked on the product, the total, and the confirm button. They are not reading every line of text. They are not examining every checkbox.
Some checkout flows exploit this by placing unwanted add-ons where attention is lowest — pre-ticked checkboxes in small print near the summary, fees in light grey text, auto-enrolled subscriptions tucked below the fold. The user isn't stupid. They're just focused — exactly as human attention works.
The user's attention is on the product, the total ($79), and the button. The two pre-ticked add-ons are in 10px light grey text — exactly where attention is lowest. Next month the total is $93.98.
The design works against the user because it's built around selective attention. The important things (product, price, button) are visually dominant. The costly extras are placed in the attention shadow. The user isn't tricked — they “agreed” to both checkboxes. But the design was explicitly built to ensure they wouldn't notice.
The honest version of working with selective attention is about placing information where the user's focus actually is — not exploiting where it isn't.
Put error messages next to errors. Put warnings near the action they warn about. Put fees near the total. If something is important enough to affect the user's decision, it should be in their focus zone when the decision is being made — not technically on the page somewhere they're unlikely to look.
Chabris, C., & Simons, D. (2010). The Invisible Gorilla. Crown Publishers. · Simons, D. J., & Chabris, C. F. (1999). Gorillas in our midst. Perception, 28(9), 1059–1074. · UK Competition and Markets Authority (2022). Online choice architecture: how digital design can harm consumers.