Hello, happy new year, I've noticed that native english speaker using ''can'' and ''can't'' with the same pronunciation, how can I understand this and use as well.
I have a London accent so I don't have this problem! However, here are some ideas:
a) pay attention to the context - which one makes more sense?
b) what is the feeling? positive or negative?
c) try to identify the /t/ sound at the end - sometimes it is like the airflow has suddenly stopped in the throat
Don't worry if someone speaks fast and you can't hear exactly if it's supposed to be <em>can </em>or <em>can't. </em>It's normal to ask people to repeat and emphasize on which word they're saying.
I agree with Stephanie. If you're familiar with IPA, I usually hear <em>can </em>being spoken with the ə sound (like the 'a' in 'about') in American English. <em>Can't </em>sounds more like the word <em>can </em>(the tin container, not the verb) or <em>tan</em>.