If you search for the definition of decision making here are some samples of what you'll find:
Other disciplines may have a slightly different definition of decision making, for example, games theory or computer programming have variations in their uses for the terminology. And even if you compare models there are variations in each models definition.
And when people ordinarily consider their own definition of decision making, it is typical that they consider that somehow it is a thinking process, with lots of mental activity involved in choosing between alternatives.
But this doesn't include the way some people make decisions. You may have heard people saying
So how do we explain this?
This particular definition of decision making is more useful:
The process of selecting from several choices products or ideas, and taking action.
Because when people make decisions, they actually use their whole organism, not just their thinking abilities. This whole system approach is considerably more effective than simply 'thinking it through'.
Consider, for example, when somebody uses a phrase such as "I knew at the time that I probably shouldn't have chosen this one, but I did it anyway". Usually what happens is that their system is making one choice, and mentally they choose something else. There are basically ignoring their own body wisdom. And later, of course, the bad decision comes back to haunt them!
The way around this so that you make good decisions is obviously to learn your own signals in your body so that you recognize them when they occur. And the most important thing then, of course, is to pay attention to the signals!
There are many approaches and they include the idea of 'sleeping on it', where someone delays making a decision until the following day. This can be very useful in allowing somebody's whole system to align to one particular choice. But even if people sleep on the decision they are still prone to overriding the body signals, because in our culture more emphasis is put on the cognitive aspects of decision making.
The evidence for this lies not just in the definition of decision making (see above) but the emphasis in most of the decision making models is on the strategies for making the most rational, logical and sensible choice. And then there is satisficing!
You can read an overview of decision making here with a brief description of models, styles and evaluating decisions.