Final answer:
Pecking the keys by pigeons based on line angle or form as per the state of the houselight shows conditioned discrimination, a learned behavior developed through shaping and conditioning.
Step-by-step explanation:
When pecking the keys is based on line angle or form depending on the state of the houselight (on/off), we can say that the pigeon shows conditioned discrimination. This is a type of learning where an animal, such as a pigeon, can differentiate between stimuli based on certain conditions, in this case, the state of the houselight. It's a behavior shaped through the process of conditioning, where the pigeons learn to associate certain responses with specific outcomes under certain circumstances. This kind of behavior is often developed through training methods like those used by B.F. Skinner, known as shaping, to teach pigeons complex behaviors.