How can you be sure that there is an actual person at the other end of the chat line?

With today's high technology, it's really hard to tell if you are chatting with a computer or a real person.

However, it is distinguishable. You can tell that you are chatting with a computer if one or more of these thing are happening.

1) repetition of same phrases

2) quick reply

3) irrelevant answer to a question
4) random irrelevant phrases