Ivan Pavlov is best known for his work on “conditioned reflex”, typified by what is called the Pavlov’s Dog experiment.
What Pavlov did was very simple. He put a dog alone in a room and, whenever it was meal time, he would first ring a bell and then give the dog his food. The procedure was repeated day after day. Finally a point came when the dog would start drooling at the mere sound of the bell.
Now see how the wise men, of every hue, deployed this as a device.
The moment you light a candle or a lamp, the moment the aroma of incense sticks impacts your nose, the moment you lay down your meditation mat, the moment the sound of church and temple bells strikes your ears… some minds become ready for prayer.