Getting the finger

The first time I ever got the finger in America I was in Texas in the 80's. I was at a stop sign and the car in front of me has this finger sticking out of the sun roof. I think to myself, "hum! why is she sticking her finger out of the roof, how strange?" I wonder to myself if she is perhaps drying her nail (she had the most fascinatingly beautiful long nail with pink nail polish) or testing