Electromagnetic Signals Influencing Human Thought?

For a long time now* it has been perfectly intelligent, rational and
scientific to pose the question, "Would it be possible for the thought
processes of individuals to be influenced by electromagnetic signals
engineered by others?"

It is my belief that any intelligent, rational and scientific answer
to this question would have to be based on experimental evidence.

Can anyone offer any intelligent, rational and scientific explanation
as to why no such answer appears to have been established?

Keith P Walsh

* I'd say at least 75 years.