Question

read the passage.
fast or slow?
the human brain can be thought of as having two different modes. daniel kahneman, an influential psychologist, labels one the \fast\ mode of thinking and the other the \slow\ mode. in the fast mode, according to kahneman, we make decisions using our intuitions and emotions. the sight of a spider may activate the fast mode and lead a person to scream. the same persons slow mode might decide (after a moment) that the spider is not actually a threat. in the slow mode, we make decisions using reason and logic. the slow mode is helpful in complex situations where the right choice is not always clear. however, because the slow mode uses more mental resources than the fast mode, our brains cant rely on it all the time. the instincts that drive the fast mode of thinking save us a great deal of time and energy.
what is the main, or central, idea of the passage?
the brains \fast\ mode often uses emotions, not logic, to guide its decision - making.
the sight of a spider would trigger different responses from the brains \fast\ mode and from its \slow\ mode.
the \fast\ mode of thinking is helpful for reacting quickly, while the \slow\ mode is helpful for analyzing complex situations.

Explanation:

The passage first introduces the two - mode thinking concept by Daniel Kahneman. Then it gives an example of a spider to show how the fast mode uses intuitions and emotions and the slow mode uses reason and logic. It also mentions the advantages of each mode: the fast mode for quick reactions and the slow mode for complex situations.

Answer:

The "fast" mode of thinking is helpful for reacting quickly, while the "slow" mode is helpful for analyzing complex situations.