How to tell whether or not a security is traded by a machine?

[jacknapier]

I just read this article saying that most of the time you are trading against a computer. I'm wondering if there is a way to determine whether or not a particular symbol is not being traded by a machine? I know that low volume would be an indicator. I couldn't imagine a computer trading a symbol with 50k shares traded a day.

 

[new_trader]

I just read this article saying that most of the time you are trading against a computer. I'm wondering if there is a way to determine whether or not a particular symbol is not being traded by a machine? I know that low volume would be an indicator. I couldn't imagine a computer trading a symbol with 50k shares traded a day.

What exactly does "trading against a computer" mean? There are possibly 1000's of traders each making decisions about whether they go long or short at any particular time. Yet this article claims that each of them is assigned a computer that trades against them? The whole notion of 'Man Vs Machine' is pure B.S.