Every few weeks, someone asks why we spell it "behavioural" instead of "behavioral." The honest answer: because we're building for India, and Indian English follows the British convention — the same reason SEBI's own regulation calls it an "Investment Adviser," not an "Investment Advisor."
But the spelling is a footnote. The discipline is the same wherever the extra "u" lands. Behavioural finance — or behavioral finance, if that's what you learned it as — starts from one observation: markets are not populated by perfectly rational actors optimising expected value. They are populated by people, and people are loss-averse, overconfident, anchored to the price they first paid, and prone to mistaking a recent trend for a permanent one.
Traditional finance asks what a rational investor should do. Behavioural finance asks what an actual investor will do, and designs around that gap. That is the entire premise Accrion is built on: a portfolio is not just a set of numbers, it's a set of numbers a specific, imperfect human has to hold through a specific, uncomfortable decade.
So call it what you like. The spelling is regional. The discomfort of watching a position fall 30% and wanting to sell is universal.