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How Does the Brain Process Attraction?

A neurobiologist explains what’s going on in your head when beauty has mesmerized the eyes

We typically think of attraction as an impulse. This out-of-nowhere thunderbolt of electricity for another person. Its power is such that it’s seemingly inexplicable — the force of nature at play in all its glory. 

And yet, biology and the brain are never really inexplicable. They’re just incredibly complex. Our understanding of them is also ever-evolving. In particular, Tim Darlington, a postdoctoral associate in neurobiology at Duke University, looks for answers in our eyes, studying the dance between eye movement and brain function to better understand exactly what’s going on in our heads. 

I recently spoke with Darlington to get a better understanding of how the two tango in terms of attraction specifically, how much of what we see is perception versus reality and how we process the beautiful people across from us in much the same way as our primate ancestors.  

What are you hoping will come from your neurobiological research into eye movement?

I’m using eye movement as a window into how the brain controls movement. Eye movements are way simpler than most other body movements, which involve a ton of different muscles across several joints. Shifting the eye’s glance from one object to another essentially involves the activation of two muscles and the relaxation of two muscles. It’s a simple output, and you can easily control the input to the system during research. In an experimental setup, you can display stimuli on a screen, train people or animals to look at different spots on a screen, control the input and then measure the output with high precision because you can measure where the eyes are in space. Because you control the input and know the output, you can focus on what’s happening between the input and the output.

One day, I’d like to be able to apply what we learn from this clinically to help patients who are paralyzed, and also to be able to help patients who have movement disorders like Parkinson’s disease or Huntington’s disease, or who have traumatic brain injuries. There’s a lot of value in basic science in terms of understanding the general mechanisms of what happens in the normal brain. You have to understand that before you can go to the diseased brain and make that better. 

What tests are you performing when you do your research?

I’m specifically interested in how the brain uses sensory input relative to what direction something is moving in and how fast it’s moving, but also the expectation of where it’s going to move. If I put a dot on a screen and I ask you to keep track of the dot. It begins to move very fast, and your brain starts to develop an expectation that the dot is going to move in that one direction very fast. For one out of every 100 trials, we may slow down the speed of the dot, and your eyes will overshoot it because they expected it to be moving fast. 

What’s happening is that your brain is combining some element of expectation with the sensory input of what you’re seeing through your eyes to come up with the best estimate of where that thing is going to move so that your eye’s movement isn’t always a reflex. You can anticipate where something is going to be moving and prepare your eye-movement system to take in movement.

Smooth-pursuit eye movement would be like a sobriety test where you track the movement of a finger back and forth. The input is visual motion. There’s a visual signal moving across your retina in the back of your eye. It has a direction, and it has a speed. Your brain takes those visual signals and converts them into a motor command that generates contraction and relaxation of the appropriate eye muscles to match that direction and speed. 

Scientists in my field have done some really cool things with multiple stimuli. Someone from our lab got subjects to associate one color with a high-value reward and a different color with a lower-value reward. They had the objects of those colors start moving at the same time in different directions, and the subjects’ eyes would first deviate toward whatever object had the highest reward attached to it.

Speaking of associating eye movement with high reward values, how does this work with attraction?

Attraction is a very complicated thing. Humans are very visual creatures. Our visual system is way more developed when you compare it to that of lower mammals, and we rely on it heavily in a lot of situations. Well over 50 percent of our brain is dedicated to processing visual information in our environment, and we take in that information through eye movements. We make those eye movements because there’s a special region in the back of our eyes called the phobia. It’s the most refined area of visual acuity. It also has the types of receptors that are responsible for color vision. The whole point of eye movement is that if you catch a glimpse of something you want to look at, you want that object to fall on that spot in the back of your eye where your visual acuity is the best. That’s where you can take in that object in the highest quality, and it will send the most detailed information to the rest of the brain.

So if you see someone walking by you out of the corner of your eye who might be the physical type you’re attracted to, you may want to shift your gaze and move your eyes toward them to take in more information about their appearance to determine if they truly are your physical type. 

Studies show that you make three saccadic eye movements per second. Those are the jumpy eye movements. Studies have been done where they’ll put people in an apparatus to track their eye movements; they’ll display images and look at how the subject’s eyes move around the image to take in information. If you put someone they found attractive up there, most people will make the eye movements that are exactly what you’d expect. They’ll spend a lot of time looking at the face — the eyes, nose and mouth — and then inevitably they’ll start looking down at the chest and in the crotch area. 

Is this unique to humans, or is this how all mammals process attraction? 

This isn’t special to humans at all. Some mammals use their olfactory system — the smell system of their brain. Pheromones and smells are far more important for rodents, for example, than they are to humans. But they’ve tested monkeys, and the monkeys do the same thing: They’ll look at the face, and then they’ll start looking at the butt.