Board Thread:Questions and Answers/@comment-16103541-20141018235515/@comment-2143393-20141019004120

It actually kinda makes sense. Mikey is by far the most social out of his brothers, so he would have the best 'people skills' out of all the turtles. That would making him good at 'reading' people persay, concluding things about their actions, words, expressions, etc. Whenever his brothers are angry or sad, Mikey is usually the first to realize their emotions. Therefore, he would be the first to realize something was wrong with April's mother.

Another possibility is that ever since the whole incident with Chris Bradford, he's trained himself to develop a talent for figuring out people's intentions, as he wouldn't want to be made a fool of again.

And on a totally unrelated note, Mikey being able to realize when his brothers have strong emotions and knowing how to help them would be a possible reason why Raph seems to have the strongest brother-connection with Mikey.