A new study suggests that our hearts slow down when we make visual mistakes, providing evidence that our bodies respond to perceptual mistakes even before we realize we’ve made them. Published in biological psychologyresearch shows that conscious perception emerges from a constant dialogue between the brain and the body.
Historically, cognitive neuroscience has focused on the brain to understand how we perceive the world. However, the brain is constantly communicating with the peripheral nervous system, the neural network that connects the brain and spinal cord to the rest of the body. Scientists wanted to understand how this body-brain connection affects conscious cognition.
“My (and my colleagues’) main motivation was to better understand perceptual consciousness, a concept with many branches and no single, universally accepted definition,” said study author María I. Cobos Martin, a cognitive neuroscience researcher at the University of Granada.
“When we try to explain how we perceive the world and how conscious experience is formed, we often think almost exclusively in terms of brain activity. But humans are more than just brains. We show that the brain is in constant communication with the organs of the body. There is growing evidence, one of which is the heart. This raises an important question: If our heart beats continuously send signals to the brain, and the brain sends signals to the heart, then isn’t it reasonable to think that the way our heart beats contributes to the formation of consciousness? ”
“Ultimately, the heartbeat is the way the heart sends messages to the brain. In this study, we wanted to examine exactly how the heart (along with brain signals) is involved in the moments when perception is accurate and the moments when perception fails. Understanding this interaction is essential to seeing consciousness not as a purely cortical process, but as something that emerges from the whole body.”
To test this, the researchers recruited 30 healthy undergraduate students, but due to equipment malfunctions and excessive eye movements, the final data analysis included between 24 and 26 participants. The team used eye-tracking cameras to monitor where participants were looking and electrocardiograms to measure their heartbeats.
During the experiment, participants looked at a computer screen and were briefly shown a series of letters. The target letter was “L” and the distractor letter “O”, and both letters were always presented in different colors. Participants were asked to identify the color of the target letter.
The researchers tailored the difficulty of the task to each subject so that they could get it right about 70% of the time. The remaining 30% of the time, participants were expected to make a specific type of error called an illusion. This occurs when the brain incorrectly blends features, such as assigning the color of a distracting letter to it, even though the target letter is visible.
To test the effects of attention, the scientists also played short bursts of loud sound through headphones during half of the trials. At the end of the experiment, we introduced an unexpected change by making the target letters white from time to time so that we could later check whether participants noticed the visual change.
Behavioral data showed that although the alert made participants respond faster, it did not improve their ability to accurately match colors or shapes. People also responded faster when they answered correctly compared to when they experienced the optical illusion.
When researchers looked at physiological data, they found a consistent pattern of lower heart rates during work. Most notably, heart rates slowed more when participants experienced the visual illusion compared to when they correctly identified the target color.
“We were really surprised,” Cobos Martin said. “Initially, we expected to replicate one of our earlier findings, in which the heart slows down when very weak stimuli reach consciousness. But the pattern here was different.”
It was not possible to directly compare the stimuli in both studies because they included targets that were sometimes completely missed in previous studies. In the current study, targets were always consciously seen, but not always accurately perceived.
“This led us to explore alternative interpretations,” Cobos Martin explained. “The decrease in heart rate that we observed may reflect an internal salience signal, the body’s marking that something unexpected or important has happened, such as a perceptual error.”
This internal alert is associated with the salience network, a brain system specialized in detecting unexpected or important events. When a person makes a mistake, this network sends a signal to the body that can temporarily slow down the heart. This suggests that the body tends to provide negative feedback about errors through changes in cardiac activity.
Additionally, unexpected white text revealed hidden differences between participants. Those who did not consciously notice the white text had a greater drop in heart rate during the mistake than those who noticed the change.
“For the general public, the message is simple: your body is constantly influencing the perceptions and interpretations of those around you, often without you even being aware of it,” Cobos Martin explained. “Conscious experience is not created by the brain alone, but from an ongoing conversation between the brain and the body.”
As with all studies, there are some limitations to keep in mind. Scientists caution against assuming that the heart actually controls what we see.
“The effects we observed are very small, operate on a millisecond time scale, and do not determine what someone sees,” Cobos-Martín said. “Instead, they show that the body is subtly involved in perceptual processes that we normally attribute to the brain alone.”
“Another important caveat is that these results reflect a correlation between cardiac dynamics and perceptual outcomes. Further research is needed to understand the underlying mechanisms and to know whether cardiac activity plays a causal role. Ideally, we need a method that allows us to directly manipulate the heart-brain interaction. So the message is not that the heart controls perception, but that perception emerges from the dialogue between the brain and the body.”
Expanding this field of research could help researchers understand how the nervous system and internal organs work together to create human consciousness.
“My next goal is to go beyond finding correlations and test whether heart-brain communication plays a causal role in conscious perception,” Cobos-Martín told SciPost. “This is a difficult question, but an important one if we want to understand consciousness as an embodied process.”
“I have already applied to several funding schemes to pursue this direction. For example, my Marie Skłodowska-Curie proposal received a very high score (93.6) but could not be funded for budget reasons. Nevertheless, that evaluation, along with new unpublished data suggesting that messages from the heart to the brain differ as a function of perceptual accuracy, gave me the courage to continue.”
“Proving a causal relationship between heart and brain dynamics will take time, but every step is important,” Cobos-Martín continued. “And we believe this research can also inform ethical discussions about artificial intelligence systems that lack a physiological basis.”
“Finally, I think the main message of our research is that human behavior and conscious cognition cannot be understood by studying the brain in isolation. The brain is constantly interacting with the body, receiving signals from the heart, gut, breathing, and many other physiological rhythms. Our findings suggest that the whole organism plays a role in how we process the world around us, even in very fast perceptual decisions.”
“I would like to go beyond that and add a broader consideration,” Cobos-Martín said. “Neuroscience and AI research is beginning to explore hybrid biological and computational systems, such as brain organoids connected to computers. These organoids can already perform simple tasks, although we don’t yet know how to effectively train or optimize them. Their existence prompts us to rethink what we think is necessary for conscious processing.”
“At the same time, it is surprising that we spend so much effort trying to imagine whether artificial systems might one day become conscious, while we tend to overlook that many living things around us – animals with emotions, sensory worlds, and adaptive behaviors – may already have forms of consciousness different from us.”
“For me, all of this highlights the importance of adopting an embodied perspective. Consciousness emerges from the dynamic interaction between the brain and the body, and understanding that relationship is key both to neuroscience and to the ethical development of future AI systems.”
The study, “The Heart Knows You’re Wrong: Heart Rate Changes Associated with Perceptual Errors,” was authored by Maria I. Cobos, Pedro M. Guerra, and Ana B. Chica.
