See A Fish Think

In Japan, a group of researchers found out how to know what the fish thinks. They thought the could see a fish think. They used zebra fish as an example. They used a special machine that shows the brain. Although their test was unsuccessful, they have found out about the fish's neural link. It connects to all the body, including the fins and the tail. They also got the DNA in the neural links. They consider this a big finding.

Question
1. How come they only used zebra fish instead of other types of fish?
2. How can they improve on this experiment?
3. If they could improve on this experiment, what would they improve on.

(2013). See a fish think. Japan: Retrieved from http://discovermagazine.com/2013/september/07-see-a-fish-think