Research participants were asked to identify a word that could be associated meaningfully with each of three other words. Solutions that occurred with sudden insight were accompanied by a burst of activity in the brain's lobe.

left temporal

Explanation:

Based on the information provided within the question it can be said that these solutions were accompanied by a burst of activity in the brain's left temporal lobe. That is because the left temporal lobe is responsible for controlling memory for verbal material as well as the ability to recognize faces and objects. Therefore associating words with their meaning would fall under memory for verbal material .

b) to encourage free trade