An exceptional demand curve can result from a change in the taste of consumers. When there is a shift in consumer preferences or a change in their tastes, it can lead to a significant and sudden change in the demand for a particular product. This can result in an exceptional demand curve, where the quantity demanded at each price point differs significantly from the previous demand curve.
For example, if a new trend or fashion becomes popular among consumers, the demand for related products may increas dramatically, causing an exceptional demand curve. Similarly, if there is a sudden decline in the popularity of a product due to changing tastes, it can result in an exceptional demand curve with lower quantities demanded at each price level.