Just like us, our dogs are paying attention to what is happening around them all the time. They are reading the signals in order to determine what, if any, meaning those signals have for them and their well-being. From the moment of birth, all of us animals are interpreting the world around us for clues. What is that? Is this thing dangerous? Can I eat it? Does he like me? Is this event noteworthy? How does this relate to that?

Every time an animal makes a mental note about the meaning of something (angry owner with scowling face = dangerous to approach for petting), the brain is organizing information about the world into that which matters and that which does not, categorizing the event for future reference. This process of adding, sorting, or changing meaning is known in behavioral science as classical conditioning. Traditional behaviorists call an inherited meaning you were born with an unconditioned stimulus and a new one you pick up along the way a conditioned stimulus.

Russian physiologist Ivan Pavlov illuminated this process for the scientific community when he conditioned a dog to salivate in response to the sound of a bell that routinely predicted the presentation of food. He made a previously meaningless bell meaningful to the dog because he created a pattern between a random event and a really important one. The bell became something to pay attention to, when it had previously been meaningless to the dog.

This kind of learning by association happens in life all the time, outside of Pavlov’s laboratory. We flinch when something is thrown at our face, and feel queasy when we drive by the diner where we ate bad fish that time. We drool like Pavlov’s dog when we see the golden arches from the interstate as our stomach rumbles on a long road trip. The clinking sound of the leash being picked up wakes your dog from a dead sleep and readies her for adventure. You open a crinkly bag in the kitchen, and she is suddenly sitting at your feet. You pick up the nail trimmer, and she runs under the bed. These once-innocuous signals have taken on meaning because they relate to something else that is meaningful. And yet the new flowers on the kitchen table, or the beautiful dress you just put on for your date, or even the fact that you’re busy working on your résumé don’t seem to register at all to her. Why?

Nature is very efficient. There are not just dozens but literally millions of things happening inside and around us at any given moment. While some require our attention or a response, the vast majority of occurrences in the world around us must simply go by unnoticed. No creature can respond to every sight, smell, and sound in the world; any animal would die of neurological exhaustion if it did. So nature has filters, and it’s constantly improving them to help us sift through and sort things into categories without wasting precious time and energy on irrelevant information. It’s kind of like Google for the brain.