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How Light Affects the Brain

When it comes to our decision-making skills, there are so many different variables that can affect our brains; it’s a bit overwhelming to consider. One of the most vital and yet overlooked conditions, however, is light. We are bombarded by light rays all the time, every day, and the kind of light we’re exposed to can have a massive effect on our cognitive abilities.

In this article, we want to dive deeper into the physiology of light and the brain and how they are related.

Why Light is Crucial For Humans

In the modern era, we are inundated with light from an incalculable number of sources. For most of human history, people adapted to a standard 24-hour light cycle, with the sun as the primary source. While fire could provide some illumination at night, it wasn’t reliable enough to be considered disruptive to this cycle.

These days, however, light is everywhere. Lamps, headlights, street lights, computer screens, TVs – everything is lit up.

However, although we have all grown up in an era where light is an abundant resource, our bodies are still hard-wired for a traditional 24-hour day/night cycle. This means that by adding so much artificial light, we are adjusting the way our brains process information.

Visual vs. Non-Visual Centers

When talking about light, the most apparent effect it has on humans is our ability to see. Light particles hit photoreceptors in our eyes, which give us the right conditions to visualize the world and environments around us.

Beyond visibility, though, light can also impact non-visual centers in the brain. The most notable is our circadian rhythm. In case you’re unfamiliar with the term, circadian rhythm refers to the sleep/wake cycle to which our bodies are accustomed. As a general rule, we enter periods of wakefulness and tiredness based on chemical reactions in the brain, which are guided by the hypothalamus.

The brain uses environmental conditions to determine when to release chemicals to make us tired and to make us more awake. One of the most potent ecological factors is light. As it gets dark, our brains think that it’s time to go to sleep, so we start to feel tired. When it’s bright outside, we are more awake.

Although light is critical in maintaining this rhythm, it’s not the only factor. Because our brains are wired for a 24-hour day, they use additional triggers to tell us when to sleep and when to wake up.

As you can imagine, having so much light around us at all times can throw this rhythm out of whack. While we may be in a brightly-lit room or space, our hypothalamus can still release sleep hormones at a particular time. For example, if you usually go to bed around the same time every night, you’ll start to feel tired at that time, regardless of other factors.

Unfortunately, artificial light is just as powerful of a trigger as sunlight, which can be enough to disrupt our sleep cycle. Even worse, circadian rhythms affect more than only our sleep/wake cycle – they can impact our health in a variety of ways too.

How Light Affects Our Mood and Decisions

Outside of our circadian rhythms, light can influence a lot about how we think and how we receive the world around us. Light can make us feel tense or relaxed, and it can impact our decision-making abilities.

Because our brains are such complex organisms, moods and emotions can vary wildly from person to person, and there can be a wide array of triggers that can set them off. When it comes to light, it can affect us in a few ways, including:

Bright Light = Intense Emotions

You may think that the way you feel is more internal than external. While that’s mostly true, it appears that light can strengthen or weaken the intensity of those emotions on a subconscious level.

According to recent research by the University of Toronto Scarborough, bright light can intensify your feelings, no matter what they are. If you’re feeling sad or depressed, being in a bright space can amplify it. If you’re angry, you’ll be even madder.

The test illustrated this phenomenon by having participants rate and provide feedback on a variety of topics. For example, they were asked to rate the aggressiveness of a fictional character. When the lights were brighter, the perceived aggression was heightened. Other factors included the attractiveness of individuals, the spiciness of chicken wings, and even the flavor of a particular juice.

Low Light = Relaxed

On the other end of the spectrum, when participants of the same study were tested in low-light conditions, they were much more casual and relaxed about everything. The wings weren’t as spicy, and they rated characters are more calm and sensible.

Overall, the study does confirm how our brains react to different lighting conditions. In brighter environments, our minds are more awake, since it seems like it’s the middle of the day when we have to be as alert as possible. In darker scenarios, our brains believe that we need to get ready for sleep, so we start to feel more relaxed and serene.

Light and Color Influences

While the intensity of light can affect the way we think, the color can also influence our decision-making habits. Usually, we don’t encounter colored lights in most situations, but knowing how each hue can impact our brain can provide further context to the nature of how we think.

So, with that in mind, let’s break down the effects of each color on our brains.


These days, it seems that blue lights are everywhere. Almost all electronics utilize a blue indicator light to signal that it’s on or functioning. This prevalence means that our eyes are bombarded by this color, even if it doesn’t feel that way.

Unfortunately, blue light can affect our sleep patterns quite significantly. The hormone melatonin makes us tired, while cortisol makes us more alert. According to research, blue light activates cortisol production while limiting melatonin. The reason for this is that the sun emits blue light rays, which are undetectable to the naked eye. As you can imagine, exposure to blue light at night makes us less likely to fall asleep.

So, if you have blue-light electronics in your bedroom, it’s best to unplug them before going to sleep. Even a tiny indicator can be enough to trigger cortisol production, making you less sleepy and less likely to feel rested.

There is an upside to blue light, though. For those suffering from seasonal affective disorder (SAD), exposure to blue light in the morning can alleviate symptoms brought on by the condition. Since blue light is so effective at waking us up, it can mitigate feelings of sadness and lethargy that come from the darker months of the year.


Typically speaking, the only time we see green light is when we’re zooming through an intersection. However, it has the opposite effect of blue light on our sleep patterns, according to the same research. Apparently, if you are exposed to green light when trying to fall asleep, you feel more tired and can doze off much faster.

A study done on mice showed that they could drift off to green light in less than five minutes, while it took almost 20 minutes when they were exposed to blue light.

Other effects of green light include the creation of growth hormones and muscle rebuilding. These claims are mostly circumstantial, but the fact is that green light can have a powerful impact on both the brain and the body.


When you imagine a bright, cheery color, you most likely picture yellow. Yellow light is ideal for bringing joy and a sense of well-being. As with green, this hue is perfect for creating a calm environment for both relaxation and sleeping. Part of the reason yellow is so vibrant is that we mostly associate it with the sun. It’s also eye-catching, making it the go-to choice for items that need to get noticed immediately (i.e., a school bus).


There’s a reason red is the color of passion. Limited studies have shown that red can increase one’s heart rate, as well as a person’s intimate desires. Red light can also stimulate hunger, which is why so many food brands use red in their logos and product designs.

When it comes to other physiological effects of red light, it’s been shown to help alleviate muscle and joint pain and stiffness. Red light is also beneficial for mental stimulation, and could theoretically assist with repairing brain tissue. More studies need to be done to determine the effectiveness of red light therapy, but it looks promising.


Psychologically speaking, white light is associated with purity and new beginnings. Sterile rooms, for example, are bathed in pristine white light.

For our brains, however, this hue is almost as effective at suppressing melatonin production. Simply put, if you’re trying to sleep with white light, it will be much more of a challenge.

Overall, light can affect our brains a lot more than you may realize. The impact of the color and intensity of different lights can be powerful tools if you know what they can do. As an individual, it helps to recognize how light affects your thinking and decision-making capacity. With the right tools, you can “hack” your brain by using the right combination.


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