How does our brain form intentions and make decisions? Do we have free will?
A new study takes a fresh look at a classic Libet experiment to uncover new insights.
Key Facts:
- Researchers tested whether people can accurately report when they formed an intention to move.
- They compared brain activity to the timing people reported making a decision to move.
- The study found people can distinguish between intending to move and actually moving.
- But people unfamiliar with reporting decision times may mistakenly report them as happening earlier.
- The study adds to understanding how we experience intentions, but more research is still needed.
Source: Neuropsychologia (Vol. 185, July 2023)
When you make a choice to move, like pressing a button or picking up a glass of water, it feels like you consciously decided to do it.
But some famous experiments from the 1980s challenged this idea and suggested our brains make decisions before we’re even aware of them.
The New Experiment: Testing Free Will
Now, researchers have revisited those classic experiments using new methods to try to get a clearer picture of how we experience intentions.
Their results add some important new pieces to the puzzle.
The findings suggest that people can accurately tell when they formed an intention to make a movement.
However, people unfamiliar with reporting the timing of decisions may mistakenly think intentions happened earlier than they actually did.
Let’s look at what the researchers did step-by-step:
Measuring Brain Activity
The key experiment being re-examined was originally done by scientist Benjamin Libet in 1983.
In Libet’s study, participants had to flex their wrist whenever they felt like it while having their brain activity monitored.
They reported the time when they felt the intention to move by noting the position of a dot moving quickly around a clock face.
This allowed comparing the timing of their intention to the onset of brain activity called the “readiness potential” that happens before movement.
The readiness potential reflects the brain preparing for action.
Libet’s controversial finding was the readiness potential happened before people reported feeling the intention to move.
This led to the idea that unconscious brain activity causes our actions, before we’re even aware of deciding to move.
A new twist on Libet’s classic design
The recent study added an important new twist to Libet’s classic design.
The researchers split participants into two groups.
One group started by reporting the time when they actually moved their wrist.
The other group started by reporting the time of their intention to move.
After doing several trials of one type of report, they switched to the other.
This allowed the researchers to see if familiarity with reporting movement times affected how accurately people could distinguish between the intention to move and the movement itself.
What were the results?
The researchers looked at both the participants’ reports of their intention and movement times as well as recordings of their brain activity.
They found an interesting pattern in the results.
When the participants started by reporting movement times, they were later able to clearly distinguish between the intention and movement.
On average, they reported intentions happening about 150 milliseconds earlier than the actual movement.
But the participants who started by reporting intention times showed a much smaller difference between intention and movement times in their later reports.
This suggests that without first getting familiar with reporting the movement time, people have more difficulty accurately identifying when the intention occurred separately from the movement itself.
No Link Between Brain Activity and Intention Timing
The study also looked at whether the readiness potential in the recorded brain activity matched up with when people reported experiencing the intention to move.
If these two measures reflect the same decision process in the brain, they should closely align in time.
However, the researchers found no clear correlation between the start of the readiness potential and the reported intention times, regardless of which order participants performed the tasks.
This disconnect suggests the readiness potential may not directly reflect the formation of conscious intentions.
So it may not provide evidence our brains make decisions unconsciously.
Main takeaways from the study
What conclusions can we draw from these findings?
The results suggest a few key points:
- With practice, people can accurately distinguish when they formed an intention from when they actually moved.
- Without that practice, people may mistakenly report intentions happening earlier than they did.
- The readiness potential does not appear to directly reflect the start of conscious intentions.
More research is still needed to fully understand the processes involved in forming intentions.
But this study takes an important step forward in revealing how we experience making decisions.
It shows that familiarity with identifying the precise time movement starts makes a big difference in accurately pinpointing intentions.
This could account for some discrepancies in previous experiments.
The findings also reinforce that the brain activity and mental processes leading up to decisions are complex.
Simple explanations likely won’t capture the full picture.
There is still much more to learn about how intentions arise in the mind and their connection to motor preparation processes in the brain.
But the thought-provoking results move us one step closer to solving the mysteries of free will and conscious choice – some of the most fascinating frontiers in neuroscience today.
How the Experiments Worked: Details
The recent study testing how people experience intentions used classic experiments as a starting point.
Here’s a closer look at how these experiments work:
Reporting Movement and Intention Times
In the basic setup pioneered by Benjamin Libet, participants sit facing a special clock.
The clock has a dot rapidly rotating around the clock face, completing one revolution about every 2-3 seconds.
Participants are instructed to flex their wrist whenever they feel the urge to, and remember the clock position of the moving dot at the time they experienced specific events.
To report the time of the intention to move, they remember the dot position when they first felt the urge or inclination to flex their wrist.
To report the movement time, they remember the position when they actually started moving.
This allows researchers to compare the reported times of intentions and movements.
Recording Brain Activity
Along with reporting times, electrodes on the participants’ scalp record the electrical activity in their brain.
This lets researchers look at brain patterns leading up to the movement. The readiness potential is a slow buildup of electrical activity that starts about 1 second before movement.
It originates from brain areas involved in motor planning and preparation. Researchers can look at when this activity begins relative to the reported intention times.
Recent Advances
Modern experiments use more sophisticated analyses of brain activity than early studies.
This allows looking at patterns across many areas, not just limited measurements.
Researchers can also use calibration methods to help participants more accurately get a sense of the milliseconds timescale for reporting fast events.
These kinds of improvements provide additional insights beyond classic experiments alone.
Experiment (step-by-step):
- Participant sits facing clock with moving dot.
- Electrodes on scalp record brain activity.
- Participant flexion wrist spontaneously whenever they feel urge to.
- Participant remembers clock dot position at first urge to move (intention time).
- After moving, participant remembers position when movement began (movement time).
- Researchers compare intention and movement times.
- Researchers analyze brain recordings time-locked to movement for readiness potential.
- Onset of readiness potential compared to intention time.
- Analyze patterns across many trials and participants.
The Hidden Complexity of Simple Choices
Even simple acts like flipping a switch or pressing a button involve hidden complexity in how the brain forms intentions and executes actions.
Decades of research have probed the mysteries of how choices happen, but many questions remain unanswered.
Here are a few reasons why the process is so difficult to unravel:
The Mind-Brain Gap
Scientists can study correlated brain activity and behavior, but getting inside the “black box” of someone’s mind to experience decisions directly is impossible.
This means the connection between brain processes and subjective experience can’t be directly observed.
“The Big Picture” Problem
Experiments break actions down into discrete events with precise timings to analyze what leads to what.
But in real life, our brains operate as unified systems.
Isolating intention, preparation, and movement artificially may not reflect how it works within ongoing brain function.
It’s Complicated in There
Even simple acts require coordinated activity across extensive networks of brain areas.
Areas involved in intention, preparation, awareness, and movement are interlinked in complex ways.
Timing depends on interactions between many subcortical and cortical regions.
No Clear Line Between Unconscious and Conscious
Exactly when unaware processing becomes conscious intention is blurred.
Intentions likely gradually emerge from networks integrating information over hundreds of milliseconds or more.
There may not be a discrete point when unconscious processing switches to conscious intention.
Subjective Experience is Fleeting
We have a continual feeling of conscious control.
But pinpointing precise moments when an urge to act appears or a decision is finalized is difficult because specific events are ephemeral.
Our perception of seamless experience may not capture the underlying complexity.
Inventive New Research Methods
Progress requires moving beyond classic simple experiments by using new techniques to tap into the details while not losing sight of broader context.
Creative ways to monitor brain-wide activity and subtle aspects of awareness while people behave naturally are keys to advancing knowledge.
Though there are challenges, unraveling how intentions spring into our awareness and guide actions remains an exciting area to watch.
New findings will fundamentally shape our comprehension of one of the most profound aspects of human nature – the capacity to make choices.
A Look Behind the Scenes: How Intention Research is Done
Intention research using neuroscience methods involves a unique set of challenges not found in many other fields.
Here are some examples of what goes on behind the scenes:
Keeping Things Spontaneous
Participants need to spontaneously make decisions about when to move without external cues.
Repeating identical movements over and over becomes automatic, so encouraging natural variability is important.
Research assistants often monitor movements to make sure they remain spontaneous.
Monitoring Awareness
Researchers don’t want participants consciously strategizing about when to move or how to alter their decisions.
They monitor performance and check in with participants to make sure they remain engaged but act spontaneously during the experiments.
Reading Between the Scalp Lines
Though scalp recordings provide useful surface readings of brain activity, they miss all the important activity happening in subcortical structures beneath the cortex.
Researchers combine scalp data with other methods like functional MRI to infer the role of deeper brain areas.
Mastering the Mental Timescale
Reporting the precise millisecond time of intentions requires training so participants learn how brief time intervals translate into positions on the clock face.
Analog clocks work better than digital ones because they better represent the continuous flow of time.
Seeing the Forest and the Trees
Researchers analyze both aggregated data averaging across trials and individuals and detailed data from single trials to get both overall patterns and insights into variability.
Connecting both levels is important for getting a complete picture.
Keeping Participants in the Dark
Researchers don’t explain what concepts like readiness potential refer to so participants’ biases don’t influence results.
Objective self-reports of timing are needed, so keeping participants naive about expected outcomes is key.
A Dance Between Control and Naturalism
Researchers have to strike a delicate balance between experimental control and naturalistic conditions.
Highly controlled laboratory setups with strict parameters may not reflect real-world cognition, but completely natural settings come with other limitations.
The back-and-forth interplay between methods moves understanding forward.
Checkpoints on a Winding Road
There are few definitive “eureka” moments in intention research where new methods suddenly produce clear answers.
Findings gradually accumulate across replicated studies using different approaches to steadily but incrementally build understanding of this deep mystery of human behavior.
Though challenging, scientists are optimistic continued two-steps-forward-one-step-back progress will eventually unravel the puzzle of how intentions spring into awareness.
Each new experiment and observation provides a few more clues to how the mind shapes our actions.
References
- Study: (Non)-experiencing the intention to move: On the comparisons between the Readiness Potential onset and Libet’s W-time
- Authors: Dimitri Bredikhin et al. (2023)
