People aren't as rational as we would like to think.

From attentional bias — where someone focuses on only one or two of several possible outcomes — to zero-risk bias — where we place too much value on reducing a small risk to zero — the sheer number of cognitive biases that affect us every day is staggering.

Understanding these biases is key to suppressing them — and needless to say, it is good to try to be rational in most cases. How else can you have any sort of control over investments, purchases, and all other decisions that you make in your life?

To convey the breadth of cognitive biases, we've picked out 57 of the most notable ones from a much longer list on Wikipedia. [Aimee Groth contributed to an earlier version of this article.]