Cognitive load
Etymology
Central to "cognitive load theory," developed by educational psychologist John Sweller in the late 1980s, drawing on the long-standing finding that working memory can hold only a few items at a time. "Cognitive" comes from Latin cognoscere, "to get to know," and "load" carries the plain engineering sense of a burden placed on a limited system — here, attention and working memory.
noun · /KOG-nih-tiv lohd/
The total amount of mental effort being used in working memory at a given moment.
What it names
The real bottleneck behind confusion, mistakes, and decision fatigue — the mind’s limited capacity to hold and juggle information at once.
Example
The form failed not because it was hard but because it asked for twelve things at once, pushing cognitive load past the point where people finish.
Related idea
Decision fatigue is what happens when sustained load depletes you over time; cognitive load is the momentary weight on working memory right now.