Often referred as being unable to “think outside the box”, functional fixedness describes the difficulty of using an object differently from how it is normally used. This has negative effects on a person’s problem solving skills. Functional fixedness causes a person to look at a problem in one specific way. Interestingly, this bias does not appear to exist in very young children (5-year-olds); it starts to develop later in childhood (around age 7).
Karl Duncker discovered this tendency when he asked his participant to mount a candle on a wall, using only a candle, thumbtacks, and a box of matches. Most people tried to nail the candle onto the wall or wax the candle onto the wall. Only a few people used the box of matches as a recipient for the nails, tacked the box onto the wall and set the candle upright in the box to light it up.