The spotlight of attention is more like a strobe

August 22, 2018, Princeton University
Credit: CC0 Public Domain

You don't focus as well as you think you do. That's the fundamental finding of a team of researchers from Princeton University and the University of California-Berkeley who studied monkeys and humans and discovered that attention pulses in and out four times per second.

"Our subjective experience of the visual world is an illusion," said Sabine Kastner, a professor of psychology and the Princeton Neuroscience Institute (PNI). "Perception is discontinuous, going rhythmically through short time windows when we can perceive more or less."

The researchers use different metaphors to describe this throb of attention, including a spotlight that waxes and wanes in its intensity. Four times per second—once every 250 milliseconds—the spotlight dims and the house lights come up. Instead of focusing on the action "onstage," your brain takes in everything else around you, say the scientists.

Their work appears as a set of back-to-back papers in in the Aug. 22 issue of Neuron; one paper focuses on , the other on .

"The question is: How can something that varies in time support our seemingly continuous perception of the world?" said Berkeley's Randolph Helfrich, first author on the human-focused paper. "There are only two options: Is the data wrong, or is our understanding of our perception biased? Our research shows that it's the latter. Our brains fuse our perceptions into a coherent movie—we don't experience the gaps."

Perception doesn't flicker on and off, the researchers emphasized, but four times per second it cycles between periods of maximum focus and periods of a broader situational awareness.

"Every 250 milliseconds, you have an opportunity to switch attention," said Ian Fiebelkorn, an associate research scholar in PNI and the first author on the macaque-focused paper. You won't necessarily shift your focus to a new subject, he said, but your brain has a chance to re-examine your priorities and decide if it wants to.

Brain rhythms have been known for almost a century, since electroencephalograms—better known as EEGs—were invented in 1924. "But we didn't really understand what these rhythms are for," said Kastner, who was the senior author on both papers. "We can now link for the first time to our behavior, on a moment-to-moment basis. ... This is a very surprising finding, more since these rhythmic processes are evolutionarily old—we find them in non-human primates as well as in our own species."

This pulsing attention must present an evolutionary advantage, the researchers suggest, perhaps because focusing too intently on one subject could allow a threat to catch us by surprise.

"Attention is fluid, and you want it to be fluid," said Fiebelkorn. "You don't want to be over-locked on anything. It seems like it's an to have these windows of opportunity where you're checking in with your environment."

"It's an elegant way to allocate brain resources—to sample the environment and not have any lapses," said Robert Knight, a professor of psychology and neuroscience at Berkeley and a co-author on the human-focused paper.

Kastner's lab focuses on macaque research, so she reached out to Knight's lab, which does similar studies on humans. The resulting papers are unprecedented, Knight said.

"This is cross-species validation of a fundamental aspect of human behavior," he said. "I have not seen any back-to-back human and monkey papers appear anywhere ... and these are in the same issue of Neuron, a preeminent journal."

Fiebelkorn agreed: "We have an assumption that what we find in the monkey will hold up in humans, but it's rarely checked as carefully as it is here."

"Originally, we wanted to study something very different," said Kastner. "We wanted to ask how we can select objects from our cluttered visual environments. ... We were particularly looking at how the intake of visual information unfolds over time—something that is rarely done in behavioral studies—and this revealed the rhythmic structure of perception. It was a complete surprise finding."

Explore further: Pay attention – how the brain performs a background scan to help focus

More information: "A dynamic interplay within the frontoparietal network underlies rhythmic spatial attention" by Ian Fiebelkorn, Mark Pinsk and Sabine Kastner, DOI: 10.1016/j.neuron.2018.07.038

"Neural mechanisms of sustained attention are rhythmic" by Randolph Helfrich, Ian Fiebelkorn, Sara Szczepanski, Jack Lin, Josef Parvizi, Robert Knight and Sabine Kastner, DOI: 10.1016/j.neuron.2018.07.032

Related Stories

Pay attention – how the brain performs a background scan to help focus

July 13, 2018
Research reveals that vision and brain circuits perform a regular background scan, making neurons available in case they are needed to focus on a task – enabling us to pay attention.

Rhesus monkeys sense isochrony in rhythm, but not the beat

July 16, 2018
Although monkeys seem to notice regularity in rhythmic sounds, they are not able to detect the actual beat. This is the finding of a new study by researchers from the University of Amsterdam (UvA) and the National Autonomous ...

Study validates monkey model of visual perception

August 25, 2015
A new study from The Journal of Neuroscience shows that humans and rhesus monkeys have very similar abilities in recognizing objects "at a glance," validating the use of this animal model in the study of human visual perception. ...

'Mind's eye blink' proves 'paying attention' is not just a figure of speech

November 27, 2017
When your attention shifts from one place to another, your brain blinks. The blinks are momentary unconscious gaps in visual perception and came as a surprise to the team of Vanderbilt psychologists who discovered the phenomenon ...

Neuroscience research provides evidence the brain is strobing, not constant

November 17, 2017
It's not just our eyes that play tricks on us, but our ears. That's the finding of a landmark Australian-Italian collaboration that provides new evidence that oscillations, or 'strobes', are a general feature of human perception.

Findings yield better understanding of visual processing of human faces

January 25, 2017
When we are walking down a crowded street, our brains are constantly active, processing a myriad of visual stimuli. Faces are particularly important social stimuli, and, indeed, the human brain has networks of neurons dedicated ...

Recommended for you

How the brain switches between different sets of rules

November 19, 2018
Cognitive flexibility—the brain's ability to switch between different rules or action plans depending on the context—is key to many of our everyday activities. For example, imagine you're driving on a highway at 65 miles ...

Mutation that causes autism and intellectual disability makes brain less flexible

November 19, 2018
About 1 percent of patients diagnosed with autism spectrum disorder and intellectual disability have a mutation in a gene called SETD5. Scientists have now discovered what happens on a molecular level when the gene is mutated ...

Signal peptides' novel role in glutamate receptor trafficking and neural synaptic activity

November 19, 2018
Glutamate is the major excitatory neurotransmitter in the brain, and the postsynaptic expression level of glutamate receptors is a critical factor in determining the efficiency of information transmission and the activity ...

Exploring the genetic contribution to suicide risk

November 19, 2018
Researchers at University of Utah Health identified four gene changes that occur more frequently in people who died by suicide that may point to increased risk in vulnerable individuals.

'Boomeranging' back to a parents' home negatively affects young adults' mental health

November 19, 2018
The number of young adults living in their own household has dropped dramatically in the last decades in the United States for a number of economic and social reasons. In a study that will soon be published in the peer-reviewed ...

Study explains behavioral reaction to painful experiences

November 19, 2018
Exposure to uncomfortable sensations elicits a wide range of appropriate and quick reactions, from reflexive withdrawal to more complex feelings and behaviors. To better understand the body's innate response to harmful activity, ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

RobertKarlStonjek
not rated yet Aug 22, 2018
This was known from eye saccades (which we do not perceive) for over a century.
thingumbobesquire
not rated yet Aug 23, 2018
The issue of perception as a discrete phenomenon has far reaching consequences. In the revolutionary mathematical work of Bernhard Riemann's Hypothesen, the distinction of a discrete versus a continuous manifold was paramount. It is the human imagination that projects continuity in spatial relationships. This is a unique quality of the human mind that is at the basis of a principle of universal communication. The ability to conceive of a concrete infinity that subsumes the discrete is central to our creative power. That is the true source of scientific progress.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.