allowing my indoor cat to explore outside

Question
Is it bad or confusing to a cat to allow it to go outside from time to time?  AT first I would supervise her on the front lawn and she would never go beyond 10 yards or so. Now I am allowing her 20 minutes outside while I am in my apartment and she still stays close by. The other night she was out for an hour and when she came back she hissed at her sister cat, they have lived together since birth. Is this a natural reaction? She snapped out of it after 10 minutes or so but now I dont want to let her go back out fearing a personality change. She has always been so sweet with her sister and it broke my heart to see her act aggressively toward her sister. They are almost a year old.

Thanks!

~Greg

Answer
Greg,

It is good to let the cat outside to explore. They love it and it helps round them out mentally, especially if they are hunter type cats.

She may have hissed at her sister because for some reason she smelled different. Cats go by smell recognition and not by sight. She may have thought she was a different cat. It's possible that she was jumpy outside and the other inside cat startled her.

Are the cats spayed? If a tomcat bothered her, or bred her, that would cause that reaction too.

Tabbi