Wiktionary
pick up on
vb. 1 (context transitive idiomatic English) To notice, observe, learn, or understand, especially something otherwise overlooked. 2 (context transitive idiomatic English) To continue or build upon (for example, a task, analysis, or narrative), beginning from a point at which someone has previously stopped. 3 (context transitive idiomatic English) To adopt a practice in which others already engage.
Usage examples of "pick up on".
Or possibly give anything more for him to pick up on with his crazy spidey senses.
Sammy just hoped that Claire did not pick up on this with her magic perception.
It wouldn't be a whisper, would it, Tom, something you needed all this fiddly technology to pick up on?
She didn't tell him the rest of it, and he didn't pick up on the omission.