Projection bias
Assuming your future tastes, needs, and moods will look just like today's.
What it means
Projection bias is the tendency to project one's current preferences and states onto one's future self, underappreciating how much tastes, needs, appetites, and moods will change. The mechanism is a failure of perspective-taking across time: people anchor on their present state and adjust too little for the fact that the state itself is transient, so a hungry shopper imagines a hungry future and a calm planner imagines a calm execution. It is a close relative of the hot–cold empathy gap, but it is broader, covering the slow drift of tastes and the effects of adaptation as well as acute visceral states. Because the present state contaminates the forecast, people systematically mispredict their future satisfaction and make purchases and commitments that fit today but not tomorrow. It has been formalized in economics to explain over-buying durable goods in the mood of the moment and under-saving for a retirement self whose needs feel abstract. It matters because durable choices — homes, contracts, large purchases, even career moves — are made under the spell of a present state that will not last.
Examples
Shopping while hungry, you over-buy because you tacitly assume future-you will want this much food too.
Convertibles sell better on warm, sunny days and four-wheel drives just after a snowfall, as if today's weather were the weather the car will be driven in for years.
Booking the 6am flight because it is £40 cheaper: calm, rested you simply cannot imagine how much 4am you will resent the alarm.
First described in Loewenstein, O'Donoghue & Rabin (2003).