Response

There is this Zen story about a student who goes to his Guru and says, "I finally understand. The outer world is illusion. A dream."  

Whereupon the Guru punches him in the nose.

A punch in the nose does much to dispel the idea of the world as a dream. The student had it wrong, obviously. 

The Guru's physical communication to the student demonstrated:

The world is not a dream. 

It is an interaction.

Lots of animals communicate with force. Like fiddler crabs. The crabs use their big claws to signal threats to other males and also as come hither signals to females. And if other males don't pay attention and get the message wrong, the crab claws are used more forcibly. 

We wrongly suppose responses to be physical, even though they have physical results.

Response is also a perception. Muscle cells perceive the signals from neurons and respond to these by activating a molecular pump that ratchets muscle fibers together, opening and closing the claw and swinging the crab arm into play. The whole process of gnashing claws or punching students involves a tidal wave of perception, memory and response as the attacker takes aim, begins the movement, adjusts for the opponent's  sudden move to the left, and connects with the target.

Responses, like perceptions, move both inward and outward from interface between the being and its surroundings. Inward responses include a resetting of the web of memory and this results in an outward signal of this change.

Responses set the stage for re-evaluation by observation and this, in turn, results in the next phase of resetting the molecular structure of memory. Learning.