From Wikipedia:

Daniel Todd Gilbert (born November 5, 1957) is Professor of Psychology at Harvard University. He is a social psychologist known for his research (with Timothy Wilson of the University of Virginia) on affective forecasting, with a special emphasis on cognitive biases such as the impact bias. He is the author of the international bestseller Stumbling on Happiness, which has been translated into more than 25 languages and which won the 2007 Royal Society Prizes for Science Books.

His ted talk on happiness is a classic: