The reticular activating system (RAS) is a network of nerve cells that starts in the brainstem and keeps you awake and alert. It sets your general level of arousal, meaning how switched on you are. You need that alertness to pay attention to anything, but it doesn't choose what you pay attention to.
That's where the popular version goes wrong. You've probably heard that once you want a certain car, your reticular activating system starts showing it to you on every street. The new-car effect is real. It's just pinned on the wrong part of the brain. What decides what you notice is your attentional set, which is what you're currently set to look for.
I believe what you focus on shapes your reality. I learned it on a snowboard. Stare at the tree and you hit the tree. But it isn't your RAS doing it. It's what you're set to look for, and what you then do. This page covers what the RAS does, what actually picks what you notice, and a practice you can run this week.
Where this started for me
I was a professional or semi-professional snowboarder all the way through college. When you're moving fast through the trees, you don't look at the trees you're trying to miss. You look at the path you want to hit, because when you train your eyes on the thing you want to avoid, that's where your eyes lead you. That's how I describe this to people, and I've walked a lot of people through changing what they look for.
The idea itself came to me from scripture: that we're transformed by the renewal of the mind. I believe it's in Romans. (Editor's note: Romans 12:2.) I came to it from a dark place. I started focusing on the positive things, and on solutions rather than problems, and that's where I really started to train my RAS.
I still believe in the practice. In my words, "whatever you focus on you manifest into reality", as long as you focus with the right kind of intention. That's my belief, and I'll keep it labelled as mine. The rest of this page is about the part the research can show you: how attention decides what you see.
What the reticular activating system actually does
The reticular activating system is a set of connected cell groups in the brainstem. They project up into the brain and keep it awake. StatPearls, a medical reference text, describes the RAS as a component of the reticular formation, the wider web of cells running through the brainstem, and lists attention, arousal and the ability to focus among the things its neurons are responsible for. So the RAS does matter for attention, the way a power supply matters to a search engine. It decides how much is running. It has no say in what gets searched for.
The idea goes back to 1949, when Giuseppe Moruzzi and Horace Magoun proposed that activity in an ascending brainstem system accounts for wakefulness. Modern imaging has filled in the map. A 2024 study in Science Translational Medicine mapped the connections of a proposed arousal network that "sustains wakefulness", using scans of three donated human brains plus brain-imaging data, and found its nodes in the brainstem, hypothalamus, thalamus and basal forebrain. That's one study, focused on anatomy.
Arousal is the difference between asleep, drowsy and wide awake. It isn't a goal list.
Does the reticular activating system filter for your goals?
The version you've probably heard says your reticular activating system filters what reaches your awareness, so once you decide on a goal, your brain starts showing you the opportunities that match it. Write the goal down and it gets to work.
It made sense for a good reason. The effect is real. Start a business and you notice other people's businesses. Focusing on something does change what you notice. The story just needed a part of the brain to credit, and the RAS sounded right.
Here's where it goes wrong. The reticular activating system sets general alertness. It doesn't match what comes in against your goals. Being more awake makes you notice more of everything, not more of the things on your vision board. The matching happens somewhere else, and it has a name.
Your attentional set decides what you notice
Psychologists call it attentional set. It's what you're currently set to look for. Your set comes from your task, your goals and what you expect, and it decides what grabs your attention and what slides past.
The lab basis goes back to 1992, when Charles Folk and colleagues found that what grabs your attention depends on the attentional control settings your task gives you. Then in 2005, Steven Most, Brian Scholl, Erin Clifford and Daniel Simons pulled together years of experiments on unexpected objects people fail to see. Their review, titled "What you see is what you set", concluded that "the most influential factor affecting noticing is a person's own attentional goals". That's established research, and it's the honest version of what the reticular activating system story was reaching for.
The famous demonstration came earlier. In 1999, Daniel Simons and Christopher Chabris had viewers count basketball passes while a person in a gorilla suit walked through the scene. Of the 192 viewers analysed, 46% missed the unexpected event. Whether you noticed depended on how similar the surprise was to what you were tracking and how hard the counting was. There's more on the test in how selective attention works and what the gorilla test shows.
So the chain looks like this:
- You're set to look for something (a car, a goal, proof that you always mess things up).
- Things that match the set grab your attention. Things that don't, you often miss.
- What you notice becomes the evidence you count, about the world and about yourself.
- What you count shapes what you do next, and what you do changes what happens.
Step 4 is the snowboard. Your eyes go to the tree, your body follows your eyes, and you end up at the tree. There's a driving version of this in the lab: a simulator study found steering drifts toward wherever drivers look. Nothing outside you had to deliver anything.
Why you suddenly see it everywhere
The new-car effect has a name: the frequency illusion, also called the Baader-Meinhof phenomenon. The linguist Arnold Zwicky coined "frequency illusion" on the Language Log blog in 2005 for the sense that once you've noticed something, it happens a whole lot. The car was always on the road at the same rate. What changed is that it's now in your set, so each one registers, and you also remember the hits and forget the days you saw none. There's a full piece on why you suddenly see it everywhere.
Focusing on avoiding a problem keeps you looking at it
This is the part of my belief that sits closest to the attention research. Focusing on avoiding the problem maintains that the problem exists, and you keep reaffirming that reality. On a board, the tree you're trying to avoid is the thing you're set to find, so it's the thing you see, and your line bends toward it.
The same thing happens with how you see yourself. If you're set to look for proof that you always drop the ball, you'll find it, and the week you handled well won't register. A lot of what you're set to look for comes from how you see yourself. That link is a practitioner model (Maxwell Maltz's Psycho-Cybernetics and the work that followed), not a lab finding, and it's the subject of how your self-image decides what you notice. Expectations work the same way, which is where confirmation bias and seeing what you expect come in.
When you set your eyes on the path, something else changes too. What would have looked like a blocker becomes part of the solution itself.
What attention can't do
Noticing more isn't the world changing. A new attentional set changes what you see and what you act on. It doesn't move the cars, the money or other people on its own. Focus without action is a picture on a wall, and there's more on that in what a manifestation vision board actually does to your attention. And this page can't tell you whether focus shapes reality beyond attention. I believe it does. The research here supports the attention part.
A one-week practice: change what you're set to look for
This takes about 10 minutes a day for 7 days. The time limit is on the practice. Nothing here promises how fast anything changes.
1. Name your current search (day 1, 5 minutes). Write one sentence you'd use to describe your week to a friend. Then write what that sentence is set to look for. "Everything's on fire at work" is set to find fires.
2. Count the misses (days 1 to 7, 5 minutes a night). Two columns. Left: what matched your sentence today. Right: what happened that didn't match, the things your set would have let slide. The right column is often longer than you expect.
3. Look at the path (days 2 to 7, 5 minutes). Pick one quality you want to see in yourself, stated as something you do ("I follow through on small promises"). Each morning, write two moments today where it could show up. Each night, log the examples you caught, including small ones. This borrows from Steve Andreas's Transforming Your Self (chapter 5, on adding future examples), where expected examples act like predictions that sharpen your attention to whether they show up. That's a practitioner model, not a lab finding.
At the end of the week, read the right-hand column from step 2 and the log from step 3 together. That's what you'd been missing, and it's what your new search found.
Your reticular activating system keeps you awake. Your attentional set decides what you notice, and you can set it on purpose, starting tonight with step 1.
Frequently asked questions
Where is the reticular activating system located?
The reticular activating system starts in the brainstem, the stalk at the base of the brain that connects to the spinal cord, and sends signals upward. A 2024 imaging study found nodes of the proposed arousal network in the brainstem, hypothalamus, thalamus and basal forebrain. Picture a brainstem network with long reach rather than a single spot.
What is the difference between the reticular activating system and the reticular formation?
The reticular formation is the wider web of nerve cells running through the core of the brainstem, and it does more than arousal. The reticular activating system is one component of it: the ascending part that keeps the brain awake and alert. Every part of the RAS sits in the reticular formation, but not every part of the reticular formation is the RAS.
What is the reticular activating system in AP Psychology?
For an exam, the plain answer is that the reticular activating system is a network of neurons in the brainstem that controls arousal, wakefulness and alertness. If a question asks what filters which stimuli you notice, the better answer is selective attention, which depends on what you're set to look for.
Is the reticular activating system the same as selective attention?
No. The reticular activating system sets how alert you are overall. Selective attention is the process that picks which things, out of everything in front of you, get processed. It's driven largely by your attentional set, meaning your task, goals and expectations. Alertness makes selection possible. Your set decides what gets selected.
Can you train your reticular activating system to manifest goals?
The RAS isn't the part to train. It sets how alert you are, and it doesn't know your goals. What you can train is your attentional set: what you look for, what you count as evidence and what you do about it. I believe focus with the right intention shapes your reality. The research supports the attention part, and the practice above works on that.
Is seeing something everywhere a sign or synchronicity?
If a repeat means something to you, this page isn't here to argue you out of it. People find real meaning in these moments. What the research can explain is why you notice the repeat: it matched what you were already set to look for. You can hold both. The useful question is what your set is tuned to right now, and whether that's what you want more of.
This page is about attention and doesn't diagnose anything. If you think ADHD is part of the picture, a clinician can assess it. If you're in a dark place, talk to a doctor or a therapist.
Sources
- Most, S. B., Scholl, B. J., Clifford, E. R., & Simons, D. J. (2005). What you see is what you set: Sustained inattentional blindness and the capture of awareness. Psychological Review, 112(1), 217–242. https://doi.org/10.1037/0033-295X.112.1.217. Established research.
- Simons, D. J., & Chabris, C. F. (1999). Gorillas in our midst: Sustained inattentional blindness for dynamic events. Perception, 28(9), 1059–1074. https://doi.org/10.1068/p281059. Established research.
- Edlow, B. L., Olchanyi, M., Freeman, H. J., et al. (2024). Multimodal MRI reveals brainstem connections that sustain wakefulness in human consciousness. Science Translational Medicine, 16(745), eadj4303. https://doi.org/10.1126/scitranslmed.adj4303. One study (anatomy of the arousal network).
- Moruzzi, G., & Magoun, H. W. (1949). Brain stem reticular formation and activation of the EEG. Electroencephalography and Clinical Neurophysiology, 1(4), 455–473. https://doi.org/10.1016/0013-4694(49)90219-9. Founding study.
- Arguinchona, J. H., & Tadi, P. (2023). Neuroanatomy, reticular activating system. In StatPearls. NCBI Bookshelf NBK549835. https://www.ncbi.nlm.nih.gov/books/NBK549835/. Reference text.
- Folk, C. L., Remington, R. W., & Johnston, J. C. (1992). Involuntary covert orienting is contingent on attentional control settings. Journal of Experimental Psychology: Human Perception and Performance, 18(4), 1030–1044. https://doi.org/10.1037/0096-1523.18.4.1030. Established research.
- Readinger, W. O., Chatziastros, A., Cunningham, D. W., Bülthoff, H. H., & Cutting, J. E. (2002). Gaze-eccentricity effects on road position and steering. Journal of Experimental Psychology: Applied, 8(4), 247–258. https://doi.org/10.1037/1076-898X.8.4.247. One study (driving simulator).
- Zwicky, A. (2005, August 7). Just between Dr. Language and I. Language Log. https://languagelog.ldc.upenn.edu/myl/languagelog/archives/002386.html. Origin of the term "frequency illusion".
- Andreas, S. (2002). Transforming your self: Becoming who you want to be. Real People Press. Chapter 5. Practitioner model.
- Maltz, M. (1960). Psycho-cybernetics. Prentice-Hall. Practitioner model.
- Romans 12:2 (ESV: "be transformed by the renewal of your mind"), named as the source of the author's own practice and not cited as evidence. https://www.biblegateway.com/passage/?search=Romans%2012%3A2&version=ESV
Written by Austin Santos from his own voice memos and notes. AI helped with research and drafting, and every source was checked against the original paper.