I came across the RAS while reading about neuroplasticity. Until that moment, I had never even heard of it. But what I learned changed my thoughts about what I see, miss, and why.
You think you see the world. But you only see what your brain has decided is worth seeing. That comes down to your RAS.
Your RAS (Reticular Activating System) is located low in your brainstem. It connects your spinal cord, cerebrum, and cerebellum. It plays a crucial role in arousal, sleep, wakefulness, and, more relevantly, in filtering attention.
It acts like a nightclub bouncer. Every second, your senses feed it more than you could ever consciously process. But the bouncer only lets in what you have told it, consciously or unconsciously, is “important”.
You hear a new word. You are sure you have never come across it before. Then, within days, you start hearing it on the radio, seeing it in articles, and catching it in conversations. That word didn’t suddenly flood the world. Your RAS simply decided it mattered.
You do not notice things because they are new or everywhere. You see them because they have been made relevant. You start training for a marathon, and suddenly, every shop window seems to be selling running shoes. That is not a coincidence. That is your RAS doing its job.
This is not a quirk. This is how your reality is constructed. Your RAS sorts your inputs. It promotes the things that align with your beliefs, fears, or desires and quietly bins the rest. So when someone says, “I never saw it that way,” they really mean, “My RAS never let it in.”
The dangerous part is that your RAS is not filtering based on truth. It is filtering based on attention. If your mind has been tuned to threat, outrage or scarcity, your RAS will serve you more of that. And it will feel real.
This means your perception of the world is not neutral. It is algorithmic, internal, not external. Your feed is not just online; it is neurological, and the feed manager is your RAS.
So, the uncomfortable truth is this: If you want to change what you see, you have to change what you tell your RAS to look for. Otherwise, you will keep living inside the same loop, mistaking the filter for the whole picture.