At Growth By Design, we believe intentional choices lead to impactful growth, whether you’re shaping a thriving organization or a meaningful life. Here, we provide the practical information, tools, and frameworks to get you there. Today we’re exploring the subtle yet powerful driver of our behaviors, the reticular activating system: what it is, why it is important, and most importantly how you can harness its power to move from reaction to proactive simply by thought alone.
Deep in your brainstem sits a network of neurons called the reticular activating system (RAS), part of the broader reticular formation that connects up into your thalamus and cortex. Where it sits is much less important than what it does. The primary function of the RAS is to regulate arousal and act as a gatekeeper for sensory information, deciding what you consciously notice and what gets filtered out. Let that sink in. A cluster of neurons is effectively responsible for what you perceive, which in turn creates your reality.
Because you’re constantly bombarded with sights, sounds, and sensations, the RAS keeps you from overwhelm by letting in only what seems relevant to your goals, concerns, and beliefs. That’s why you can hear your name across a noisy room, or suddenly notice your new car everywhere on the highway.
RAS is in the Driver’s Seat of Reality, Friends
You may be saying “yeah yeah Katie, I know my brain filters out a lot to find what is most important. What’s the rub here?” Here’s the punchline: the RAS doesn’t just filter the world; it filters it in line with what you expect to see. If you walk through life with a quiet belief that “people are generally kind,” your attention is primed to notice moments of generosity, friendliness, and care, reinforcing that story. If, instead, you carry “people are selfish,” your RAS will spotlight slights, insults, and disappointments and let the kind gestures slip into the background.
This is a lived version of confirmation bias: our brains preferentially register information that supports existing beliefs and discount disconfirming evidence. Even in simple tasks like judging which way dots are moving on a screen, people show a tendency to interpret ambiguous evidence in line with their first impression, especially when their attention is selectively tuned.
Two Everyday Examples of RAS in Action
So, to more simply state it, your RAS is the program through which every input is received or rejected in your mind. Take the following two general beliefs into consideration:
- “I’m not good enough.”
If you carry a belief that you’re inadequate, your RAS will zero in on hesitations in others’ feedback, small mistakes, or neutral expressions and interpret them as proof. Positive comments, small wins, and signs of progress get filtered out, so the belief feels more and more “true” over time. - “I always meet the right people.”
Hold a belief that opportunities and allies are everywhere, and your RAS will highlight introductions, events, and small cues (“sit here,” “talk to her”) that move you toward connection. You start to walk into rooms scanning for possibilities instead of threats, and your behavior shifts in the same direction.
In both cases, the RAS is doing its neutral job (i.e., running its program); it’s your underlying narrative that determines whether it becomes a quiet saboteur or an ally. These are two very simplistic examples, so I invite you to get curious about what beliefs you’ve programmed your RAS with. A good way to know what program your RAS is running is to start noticing your reactions to things. When someone cuts you off do you reflex in harsh judgment, or give grace thinking they may be in a hurry?
How to Start Rewiring Your RAS in Daily Life
You can’t flip a switch on the RAS, but you can train what it treats as important through consistent focus, language, and behavior. Think of it as giving that inner “bouncer” a clear guest list.
Visualize and feel the future state
- Vivid mental rehearsal, by seeing and feeling yourself acting in a new way, can prime the brain as if the experience were already real, biasing attention toward congruent opportunities. That’s why elite performers obsess over mental imagery: they’re training their RAS to recognize the path to the outcome they’ve rehearsed.
Set ridiculously specific intentions
- The RAS is exquisitely sensitive to specificity: “I want more connection” is vague; “I’m going to initiate one meaningful conversation today” is something it can tag and notice cues for.
- Quick tip: Writing those intentions down daily strengthens the filter. Larry Kendall, in Ninja Selling (one of my all-time favorites!), teaches that putting key goals on paper trains your RAS to notice opportunities that support them. I write mine every morning a whopping 25 times (don’t worry it takes only 5 minutes).
Use focused questions as mental GPS
- Questions aim your attention: “Why do I always mess this up?” makes your brain search for confirmatory evidence; “What’s one thing I did better today?” turns your RAS toward growth. Ask the same empowering question often enough and your brain starts answering it proactively, showing you data you used to miss.
Curate your inputs
- Your RAS learns from repetition. What you repeatedly hear, read, or talk about becomes “this matters.” When you surround yourself with stories of agency, resilience, and possibility (books, people, podcasts), you’re feeding your filter with a very different definition of “normal.”
Can people be trusted? Do things work out for you? Are you capable of learning anything if given reasonable time and resources? (these are some of my beliefs I use to program my RAS, and I can promise you they have helped me increase confidence and peace regardless of outcomes).
You are not controlled by your environment. You are controlled by what you notice in your environment.
For me, understanding the RAS and how to harness its power is the single most valuable knowledge I’ve gained. After feeling incongruence between what I want and what I’ve experienced at times, I have come to know that the privilege of living into your potential (a journey we are all on) starts with a strongly tuned RAS. It is my hope that even this brief review of such a crucial function we all share helps you on your way to fulfillment.
Onward and upward!
Katie
A few of my favorite resources on RAS for my fellow extra credit friends
- Books
- Videos
- Research
Growth By Design 
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