
I finally figured out the essential difference between Penny and Tasha.
When Penny was taken for a ride in the car-car, she managed to leap from the front seat to the back over and over again without so much as jogging the driver's elbow. She understood the basic workings of an automobile and would never have considered interfering with the vehicle's operator.
When we had no other choice than to take Tasha for a drive, she was certain that her rightful place must be in the operator's lap, and not even the most vicious elbow driven into her chest could even slightly dent her determination to become co-occupant of the driver's seat.
Tasha was a good doggie, but not a bright one.