He made use of the fact that a female grackle will go up to singing loudspeakers and adopt a soliciting posture as if waiting to be mated. Her tendency to do so declines, however, as she gets bored with the song. Only if the loudspeaker starts singing a new song will her soliciting start afresh. Such “habituation” is just a property of the way brains work; our senses, and those of grackles, notice novelty and change, not steady states.
