Hey man! Thank you for the good questions! Yes, screaming and appear big is usually what you should do in case the animal looks like it is not going to run away.

As for eye contact, you should not look at wolves or bears in the eyes. Why? Because they do not see you as a prey. They see you as a threat. Keeping eye contact with them is like challenging them. It will only make them more aggressive as it will confirm their beliefs that you are an aggressive threat.

As for cougars, and most felines, you should look at them in the eye at all times because they do think of you as a prey. Making sure to keep eye contact make them think that you are confident in your chance of wining the confrontation and therefore that you will not go down without inflicting injuries to the animal yourself.