Hmm. I will say from past experiences I've only found the 'valley girl' accent to be in certain parts of California, and not representative of Californians. Growing up I remember when my sister and her friends adopted this style of speaking for a time. Usually at school, this was (from my perception) to project an air of being disinterested in bored in conversation toward authority figures. I also found it when someone wasn't capable of demonstrating a deep knowledge of something (where the bias comes into effect). I know it's incorrect, but I have many friends that think Californians don't have an innate accent and I've often thought this about how I sound when going elsewhere.

I think your comment makes sense, and I appreciate the way you detailed this.