What Did I Just Do?

When I was about 20 years old I had a summer job as a courier at a car repair shop. My job was to drive around the town and fetch spare parts from different forge shops and retailers. All these places had something in common: the calendars of half-naked girls were hanging everywhere I went. Once, on a hot summer day I was again driving somewhere. The lights turned red, and a young woman walked past the street wearing a miniskirt and a tight top. Suddenly I noticed myself whistling out loud, alone in my car. I experienced my behavior really surprising, taking on account that I am a heterosexual woman.