Visual symmetry is fundamental to how we organize and recognize objects in our environment. Our brains can quickly and accurately detect symmetrical patterns, even when they appear at the periphery of our vision. In a new study published in Psychophysiologyresearchers found that although alcohol influences certain brain activities related to visual perception, the ability to detect symmetry remains largely intact even under the influence.
Previous studies have shown that our brains can detect symmetrical patterns quickly and efficiently, even in difficult conditions like visual noise or peripheral presentation. This ability is rooted in extrastriate visual areas, specialized in recognizing and processing symmetrical patterns, contributing significantly to our perception of the order and structure of our environment. However, most of these studies were conducted in controlled laboratories.
The researchers sought to determine whether pharmacological changes, including alcohol consumption, could disrupt this perception of symmetry. Since alcohol inhibits the central nervous system and affects various cognitive and perceptual processes, they hypothesized that it might also impact how extrastriate visual areas perceive and process visual symmetry.
“We were interested in the robustness of our symmetry network in the visual system. Previously, we tried to disrupt it by trying to overload the visual system with a memory task. In the present study, we tried a psychopharmacological disruption,” explained study author Elena Karakashevska, a postgraduate researcher and statistics tutor at the University of Liverpool.
In a pilot study involving 13 social drinkers, researchers were surprised to find that alcohol seemed to improve the brain’s response to symmetry. This unexpected finding suggested that alcohol might disinhibit the visual cortex, making it more sensitive to symmetry, a result that warranted further investigation and replication.
“With our pilot study, we observed that alcohol increases the perception of symmetrical images,” Karakashevska said. “This could have explained the ‘beer glasses effect’ or why people seem more attractive to us after having a few drinks. As good and sober scientists, we replicated the study.
To verify the results of the pilot study, the researchers conducted two new experiments with larger samples. The first, called the Oddball task, involved 26 participants who discriminated colors in symmetrical and random patterns. The second, the regularity task, involved another group of 26 participants who distinguished between regular (symmetrical) and random patterns without regard to color.
Participants were recruited from a college campus and were screened to ensure they had no history of alcohol or substance use disorders. They consumed a low-fat meal before each session and refrained from consuming caffeine. Breathalyzer readings guaranteed zero alcohol consumption before the study. The alcoholic drinks contained vodka equivalent to 0.65 g/kg body weight, while the placebo drinks contained a non-alcoholic substitute. Blood alcohol concentration (BAC) was measured throughout sessions to monitor alcohol levels.
Participants sat 57 cm from a monitor displaying the visual patterns and completed the tasks while their brain activity was recorded using electroencephalography (EEG). Stimuli consisted of patterns with either 100% symmetry or random arrangements. Participants in the Oddball task indicated the color of the patterns, while those in the Regularity task indicated whether the patterns were regular or random.
The researchers found that, unlike in the pilot study, alcohol slightly reduced the brain’s response to symmetry in the Oddball task, rather than enhancing it. In the regularity task, alcohol had no significant effect on the symmetry response. Despite these differences, all conditions produced a significant symmetry-related brain signal, known as sustained posterior negativity (SPN), indicating that the visual system’s response to symmetry was robust in moderate alcohol intoxication.
Additionally, the study found that the N1 component of the brain response, which occurs earlier than the SPN, was consistently reduced by alcohol in both tasks. This reduction in the N1 component suggests that alcohol primarily affects early stages of visual processing rather than later stages associated with symmetry perception. These results indicate that although alcohol may slightly influence early visual processing, the overall perception of visual symmetry remains largely unchanged.
“It turned out that the initial results were a fluke and that alcohol does not impact our perception of symmetry, at least not in moderate doses in people who do not have addiction problems to alcohol. The two main take-home messages are 1) always reproduce unexpected results and 2) moderate doses of alcohol do not impact our perception of symmetry,” Karakashevska told PsyPost.
Interestingly, heavy drinkers showed an enhanced symmetric response under alcohol, while lighter drinkers showed a reduced response.
“Individual differences may partly explain the effects of alcohol on symmetry processing in the brain,” Karakashevska explained. “In our study, people who did not drink alcohol very often were more resistant to disruptions in visual processing caused by alcohol than heavy drinkers. Despite this, we can confidently confirm that both light drinkers and heavy drinkers have symmetry-related event potential.
Future research could further explore these individual differences and study other types of visual regularities beyond symmetry, such as rotational or translational patterns. Additionally, studies could examine the effects of different levels of alcohol and other substance use to understand their broader impacts on visual and cognitive functions.
“In the long term, we aim to expand the Liverpool EEG data catalog and systematically test the robustness of the visual system, as well as promote open research and conduct high-powered experiments,” Karakashevska said.
“I am a strong advocate for practicing open and transparent science and measuring real effects,” she added. “This involves recruiting large samples and pre-registering predictions and analyses. Our study is an example of why this is important. We could have used headline-grabbing results from the pilot, like “EEG brain recordings explain why we find people more attractive when we’re drunk,” but we knew that good science trumped catchy headlines, which is why we replicated the experience.
The study, “The extrastriate symmetry response is robust to alcohol intoxication,” was authored by Elena Karakashevska, Yiovanna Derpsch, Andrew Jones and Alexis DJ Makin.
News Source : www.psypost.org
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