What does the phrase of being on to something mean?

I googled it and then the page just directed me to a whole bunch of World of Warcraft game base websites,

and I'm sure that's not what I'm looking for.

The original sentence I saw which includes the phrase was "By regulating the magnitude and duration of serotonergic responses, the 5-HT transporter is central to the fine-tuning of brain serotonergic neurotransmission, I thought, as almost anyone would, 'Gosh, these fellows may be on to something.'"

And yes, as you may be thinking right now, it's an excerpt from an article about neurology.
be on to

  1. Be aware of or have information about, as in They can't pull that trick again; we're on to them now . [Colloquial; second half of 1800s]

  2. Discover something important or profitable, as in The researchers claim they are really on to something big . [Colloquial; mid-1900s]
chivalry... these fellows may be on to something.'
I would paraphrase this sentence in one of these ways:

They may be right.

They may have a valid argument.

They may be taking the correct approach to the problem.

They may have understood something about this phenomenon that no one else has understood, and their new way of looking at it may lead to very promising results.