Agency is about acting and doing, so effectors are cues to agency. Effectors are active or changeable body parts that move, influence, or otherwise affect the external world, and include humanlike hands, arms, legs, and tongues, and nonhumanlike wings, tentacles, claws, glowing abdomens (in lightning bugs), squirting ink sacs (in octopi), and on and on.

Experience is about sensing and feeling, so sensors are cues to experience. Sensors are body parts that are involved in conveying sensations to a mind. Eyes, ears, nose, antennae, and feelers are all routes through which minds learn about the world around them.

As sensations happen only inside minds, we use reactions as proxies for experience. When a dog gives a series of little sniffs followed at the end by a big shnoof, it seems to be reacting to a smell. Movements such as changing gaze direction, perking up the ears, orienting the body, and reaching to touch are apparent reactions to stimuli.

Reactions are indicators of what it is like to be inside another animal’s mind.

Dan Wegner & Kurt Gray, Mind Club