Okay, my latest attempt at cooking burgers worked perfectly. I guess 12 minutes on medium heat is what I need to do. Thanks to everyone for all the help!
My mistakes were using cooking spray--maybe my pan is no-stick to begin with?--and setting it on maximum heat. I was sort of imitating my mother, there. When Mom is in the car, she always cranks the AC to the maximum setting of 4. She never sets it to 1, 2 or 3. Likewise, with cooking, she always puts the stove on the highest setting, unless it's a recipe that specifically calls for the lowest-possible setting.
What's the difference between the various settings, I wonder. I'm told that if you cook on low, it takes longer to cook the food, but it is cooked more thoroughly.
This week, I'm only cooking food I cooked before (minus pork chops--I have no idea what I'll do with those). On Saturday, I cooked spaghetti for the first time. Water bubbled up from the pot and coated the entire stove top. And the sauce smelled like vinegar. I'm not sure what went wrong.