Making decisions is such a regular activity that it is mostly taken for granted. However, damage or abnormality in the areas of the brain involved in decision-making can severely affect personality and the ability to manage even simple tasks. Here, Barbara Sahakian and Jamie Nicole LaBuzetta discuss the process of normal decision making - our strategies for making decisions, biases that affect us, and influential factors - and then describe the abnormal patterns found in patients with conditions such as severe depression, Alzheimer's, and accidental brain damage. Using striking examples and...