Wishful thinking that gets in the way of reality and smart decision-making as policy makers who believe something to be true (like the presence of weapons of mass destruction) start acting like they have evidence to prove it true. Closely associated with faith-based decision-making and "in your dreams" thinking.
Even though casualties and the level of violence both escalate in Iraq, members of the Bush Administration keep making optimistic forecasts about freedom and democratic prospects since they are captives of the Tinkerbell Effect. If you believe in fairies, maybe the war in Iraq will turn out well after all!
just after you meet a girl that is so special like the pixie tinkerbell, and you feel happy and peaceful, as if her magic and sparkle has rubbed off on you. a very good feeling of endorphins and love.
"mate you've gone soft"
"nah its the tinkerbell effect, it will wear off in a bit... i hope"