How does your brain make split second decisions?

Researchers explore the "complex web of connections" in your brain that allows you to make split second decisions.

person at turn in the road
Credit: encierro on Adobe Stock
  • Researchers at the University of Colorado discovered the cerebellum's role in split-second decision making.
  • While it was previously thought that the cerebellum was in charge of these decisions, it's been uncovered that it is more like a "complex web of connections" through the brain that goes into how you make choices.
  • If the decision is made within 100 milliseconds (of being presented with the choice), the change of mind will succeed in altering the original course of action.

You are driving down the highway listening to music and thinking about a beach vacation in Hawaii when you realize your exit is sooner than you thought. Do you quickly change lanes to try to make your turn or do you keep going and take the next exit?

This is a split decision. Researchers at the University of Colorado Anschutz Medical Campus wanted to explore how the brain makes these quick "go---no go" decisions. Previous research on this same topic is discussed in this article of Medical News Today.

"We wanted to know how this kind of decision making takes place," said the study's senior author Diego Restrepo, Ph.D., professor of cell and developmental biology at the University of Colorado School of Medicine.

    While it was previously thought that the cerebellum was in charge of these decisions, it's been uncovered that it is more like a "complex web of connections" through the brain that goes into how you make a quick decision or choice.

    Susan Courtney, a professor of psychological and brain sciences, found in her 2017 study that these quick decisions involve extremely fast coordination between an area of the premotor cortex and two areas in the prefrontal cortex.

    Restrepo's team looked at the cerebellum's molecular layer interneurons (MLIs). In a Pavlovian twist, mice were rewarded with sugary water after smelling a "rewarded odorant." When an "unrewarded odorant" was released into the air, they were taught to avoid licking the spout. If they took a lick, they were sent to mouse timeout. After a few rounds, the mice learned the trick: lick to this smell, scurry away at that smell. Then Restrepo messed with their brains by throwing in chemogenetic agents that threw off their olfactory sense.

    The cerebellum, or "little brain," sits just above the brainstem. Traditionally, it is responsible for the coordination of voluntary movements as well as motor functions like balance, posture, and coordination. It has also been linked to emotional control, such as in our fear and pleasure responses, and is associated with non-motor conditions such as autism spectrum disorders.

    Research on cerebellum damage results in a variety of issues, including difficulty with balancing, errors in the force and speed of movement, gait impairment, and even decreased muscle tone. As the cerebellum changes with age, it's especially important to exercise in order to keep that region functioning optimally for as long as possible.

    Photo: StunningArt / Shutterstock

    This understanding of the cerebellum's role in decision-making is new. Because the mice became less confident in their choices after the release of those agents, it appears the cerebellum is partly responsible for quick decision-making responses.

    Restrepo notes that the cerebellum is responsible for a lot of learning—perhaps unsurprisingly, given its proximity to the spinal cord and its influence on motor patterns. Split-second decisions are an old evolutionary necessity and would have started evolving quite early on. As he says,

    "We found an entire subset of brain cells that change after learning. It sheds further light on how the cerebellum functions and the complex web of connections that go into quick decision making."

    How long does it take to make a split decision and have good results?

    The researchers in Susan Courtney's study highlighted that timing is everything when it comes to these quick decisions. If the decision to change is made within 100 milliseconds (of being presented with the choice), the change of mind will succeed in altering the original course of action. However, if it takes at least (or more than) 200 milliseconds, the chances of the change succeeding are significantly less.

    This is what aliens would 'hear' if they flew by Earth

    A Mercury-bound spacecraft's noisy flyby of our home planet.

    Image source: sdecoret on Shutterstock/ESA/Big Think
    Surprising Science
    • There is no sound in space, but if there was, this is what it might sound like passing by Earth.
    • A spacecraft bound for Mercury recorded data while swinging around our planet, and that data was converted into sound.
    • Yes, in space no one can hear you scream, but this is still some chill stuff.

    First off, let's be clear what we mean by "hear" here. (Here, here!)

    Sound, as we know it, requires air. What our ears capture is actually oscillating waves of fluctuating air pressure. Cilia, fibers in our ears, respond to these fluctuations by firing off corresponding clusters of tones at different pitches to our brains. This is what we perceive as sound.

    All of which is to say, sound requires air, and space is notoriously void of that. So, in terms of human-perceivable sound, it's silent out there. Nonetheless, there can be cyclical events in space — such as oscillating values in streams of captured data — that can be mapped to pitches, and thus made audible.


    Image source: European Space Agency

    The European Space Agency's BepiColombo spacecraft took off from Kourou, French Guyana on October 20, 2019, on its way to Mercury. To reduce its speed for the proper trajectory to Mercury, BepiColombo executed a "gravity-assist flyby," slinging itself around the Earth before leaving home. Over the course of its 34-minute flyby, its two data recorders captured five data sets that Italy's National Institute for Astrophysics (INAF) enhanced and converted into sound waves.

    Into and out of Earth's shadow

    In April, BepiColombo began its closest approach to Earth, ranging from 256,393 kilometers (159,315 miles) to 129,488 kilometers (80,460 miles) away. The audio above starts as BepiColombo begins to sneak into the Earth's shadow facing away from the sun.

    The data was captured by BepiColombo's Italian Spring Accelerometer (ISA) instrument. Says Carmelo Magnafico of the ISA team, "When the spacecraft enters the shadow and the force of the Sun disappears, we can hear a slight vibration. The solar panels, previously flexed by the Sun, then find a new balance. Upon exiting the shadow, we can hear the effect again."

    In addition to making for some cool sounds, the phenomenon allowed the ISA team to confirm just how sensitive their instrument is. "This is an extraordinary situation," says Carmelo. "Since we started the cruise, we have only been in direct sunshine, so we did not have the possibility to check effectively whether our instrument is measuring the variations of the force of the sunlight."

    When the craft arrives at Mercury, the ISA will be tasked with studying the planets gravity.

    Magentosphere melody

    The second clip is derived from data captured by BepiColombo's MPO-MAG magnetometer, AKA MERMAG, as the craft traveled through Earth's magnetosphere, the area surrounding the planet that's determined by the its magnetic field.

    BepiColombo eventually entered the hellish mangentosheath, the region battered by cosmic plasma from the sun before the craft passed into the relatively peaceful magentopause that marks the transition between the magnetosphere and Earth's own magnetic field.

    MERMAG will map Mercury's magnetosphere, as well as the magnetic state of the planet's interior. As a secondary objective, it will assess the interaction of the solar wind, Mercury's magnetic field, and the planet, analyzing the dynamics of the magnetosphere and its interaction with Mercury.

    Recording session over, BepiColombo is now slipping through space silently with its arrival at Mercury planned for 2025.

    Learn the Netflix model of high-performing teams

    Erin Meyer explains the keeper test and how it can make or break a team.

    • There are numerous strategies for building and maintaining a high-performing team, but unfortunately they are not plug-and-play. What works for some companies will not necessarily work for others. Erin Meyer, co-author of No Rules Rules: Netflix and the Culture of Reinvention, shares one alternative employed by one of the largest tech and media services companies in the world.
    • Instead of the 'Rank and Yank' method once used by GE, Meyer explains how Netflix managers use the 'keeper test' to determine if employees are crucial pieces of the larger team and are worth fighting to keep.
    • "An individual performance problem is a systemic problem that impacts the entire team," she says. This is a valuable lesson that could determine whether the team fails or whether an organization advances to the next level.
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