Some people, including me, cannot have imagined visual experiences. We cannot close our eyes and conjure an experience of seeing a loved one's face, or imagine our lounge room layout — to consider if a new piece of furniture might fit in it. This is called "aphantasia", from a Greek phrase where the "a" means without, and "phantasia" refers to an image. Colloquially, people like myself are often referred to as having a "blind mind."

While most attention has been given to the inability to have imagined visual sensations, aphantasics can lack other imagined experiences. We might be unable to experience imagined tastes or smells. Some people cannot imagine hearing themselves speak.

A recent study has advanced our understanding of people who cannot imagine hearing their own internal monologue. Importantly, the authors have identified some tasks that such people are more likely to find challenging.

What the study found

Researchers at the University of Copenhagen in Denmark and at the University of Wisconsin-Madison in the United States recruited 93 volunteers. They included 46 adults who reported low levels of inner speech and 47 who reported high levels.

Both groups were given challenging tasks: judging if the names of objects they had seen would rhyme and recalling words. The group without an inner monologue performed worse. But differences disappeared when everyone could say words aloud.

Importantly, people who reported less inner speech were not worse at all tasks. They could recall similar numbers of words when the words had a different appearance to one another. This negates any suggestion that aphants (people with aphantasia) simply weren't trying or were less capable.

A welcome validation

The study provides some welcome evidence for the lived experiences of some aphants, who are still often told their experiences are not different, but rather that they cannot describe their imagined experiences. Some people feel anxiety when they realise other people can have imagined experiences that they cannot. These feelings may be deepened when others assert they are merely confused or inarticulate.

In my own aphantasia research I have often quizzed crowds of people on their capacity to have imagined experiences.

Questions about the capacity to have imagined visual or audio sensations tend to be excitedly endorsed by a vast majority, but questions about imagined experiences of taste or smell seem to cause more confusion. Some people are adamant they can do this, including a colleague who says he can imagine what combinations of ingredients will taste like when cooked together. But other responses suggest subtypes of aphantasia may prove to be more common than we realise.

The authors of the recent study suggest the inability to imagine hearing yourself speak should be referred to as "anendophasia," meaning without inner speech. Other authors had suggested anauralia (meaning without auditory imagery). Still other researchers have referred to all types of imagined sensation as being different types of "imagery."

Having consistent names is important. It can help scientists "talk" to one another to compare findings. If different authors use different names, important evidence can be missed.

We have more than 5 senses

Debate continues about how many senses humans have, but some scientists reasonably argue for a number greater than 20.

In addition to the five senses of sight, smell, taste, touch and hearing, lesser known senses include thermoception (our sense of heat) and proprioception (awareness of the positions of our body parts). Thanks to proprioception, most of us can close our eyes and touch the tip of our index finger to our nose. Thanks to our vestibular sense, we typically have a good idea of which way is up and can maintain balance.

It may be tempting to give a new name to each inability to have a given type of imagined sensation. But this could lead to confusion. Another approach would be to adapt phrases that are already widely used. People who are unable to have imagined sensations commonly refer to ourselves as "aphants." This could be adapted with a prefix, such as "audio aphant." Time will tell which approach is adopted by most researchers.

Why we should keep investigating

Regardless of the names we use, the study of multiple types of inability to have an imagined sensation is important. These investigations could reveal the essential processes in human brains that bring about a conscious experience of an imagined sensation.

In time, this will not only lead to a better understanding of the diversity of humans, but may help uncover how human brains can create any conscious sensation. This question — how and where our conscious feelings are generated — remains one of the great mysteries of science.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

"The more often a population experiences disturbances or downturns, the more likely it is to be able to recover faster the next time around," study leader Philip Riris, an archaeologist at Bournemouth University in the U.K., told Live Science.

This seesaw between vulnerability and resilience was particularly strong among early farmers and herders, Riris and his colleagues found. Agricultural communities throughout history experienced more downturns overall than other societies, such as hunter-gatherer groups, but they also recovered from these downturns more quickly than other groups. 

"It's an important paper," said Dagomar Degroot, an associate professor at Georgetown University who studies how climate change influenced human history and who was not involved in the research. "There is a lot of really influential work on the collapse of societies faced with climate change," Degroot told Live Science, "but a focus on resilience and only resilience is significantly rarer."

Historians and archaeologists have published many case studies on individual societal crises, Riris agreed. But it's hard to compare these experiences across space and time. He and his team pulled together data from 16 separate archaeological sites around the globe, spanning from South Africa to Canada, with data stretching back as far as 30,000 years ago. 

Related: What's the deadliest month of the year?

To determine downturns and recoveries, the researchers used a method called "dates as data." Each site had records of radiocarbon dating, which gives an age for organic materials based on the decay of carbon-14, a radioactive form of carbon. Previous studies have established that the number of carbon-14 dates available for a certain time and place is correlated with population. When there are more people, it means more activity, buildings, trash heaps and firepits to excavate and date. 

Most of the downturns in the study took place on decades-plus timescales and had a variety of causes, ranging from environmental change to societal upheaval. In some cases, the researchers had specific historical or climatological information about what those crises were, such as a cold snap in Norway that led to crop loss. Farmers and herders may be inherently more vulnerable to disaster, Riris said, since one bad growing season or a drought can mean immediate famine. But agricultural and herding societies also may be well positioned to recover from disaster. 

"The winners [after a disturbance], either they're just lucky or they have some sort of technology or practice or behavior or social institution that means that they did better during the crisis," Riris said. "As a result, they're more likely to pass down that learning, that aspect of culture that will enable their descendants to do better down the line." 

The archaeological findings mesh well with historical case studies, said Degroot, who has researched resilience in the Dutch Republic in the face of the Little Ice Age in the 17th century. "I had found those things for a very narrow case study," he said, "and here the authors find them for a much broader set of case studies." 

Whether modern humans can pull directly from these lessons is less certain, Degroot said. All of the societies in the study were preindustrial and might have little in common with today's global order. However, Riris said, the ability to compare societies and look for patterns is important. 

"It provides that overarching framework that will allow resilience to be tackled systematically," he said. 

No, we’re not talking about the next instalment of James Bond, but the incredible female scientists in the "Curie Society" series of YA graphic novels.

Following the exploits of teen science prodigies Simone, Maya and Taj, the two books in the series are action-packed adventures where the main protagonists learn how to use their gifts to become the next secret agents in The Curie Society — a secret organization formed to support exceptional female scientists around the world (and save it at the same time).

Ahead of the second book's launch, we spoke to MIT professor Ritu Raman, one of the lead science advisors on the series, about how graphic novels can help promote STEM education, why diversity is so important and what it's like to be immortalized in comic book form.

Alexander McNamara: How did you get involved in the making of the Curie Society books?

Ritu Raman: I met Heather and Adam [Einhorn and Staffaroni, authors of the books] several years ago when I was postdoc at MIT, and we were talking about how there's a lack of content for preteen and teenage girls that shows science in both an exciting way, but also an accurate way. Something that motivates people, but then also shows them, within reason, what's going on in the world of STEM today.

When Heather and Adam did the first book, they talked to a bunch of different scientists and engineers from a variety of different perspectives. There was a huge collaborative effort to put the first story together, which I think was particularly important when they're fleshing out the three main characters and their origin story.

AM: What was your role in the series and how did you help in its creation?

RR: It changed between books. In the first, they talked to a lot of different scientists who do different kinds of work and had different paths to science. I think that was really important for them to take bits and pieces of people's authentic experiences and weave them into the characters.

Part of my story is moving around a lot growing up, and as a result I skipped a lot of grades bouncing between different schools. And so of the three characters, Simone's experience of being younger and not necessarily emotionally matched in maturity to the place that she is, while being matched scientifically, comes from me. 

Then in the context of Maya, who is supposed to be South Asian or Indian, the cultural exploration of science and other things, I think come a little bit from myself. The third character [Taj], is polar opposite from me, but honestly, reminds me of one of my close friends.

In the first book I shared my experience and provided feedback on a little bit of the science, but actually we talked more about depictions of bioethics and how scientists do or don't think about the consequences of their work. Who should be in the room when these decisions are being made? How do we portray a villain who starts off sort of as a good scientist and maybe things go wrong? I was providing feedback more at that level.

In the second book, they decided to pursue a strategy of having one main scientist to work with, and so I got to see the story and help craft it from very early visions. I did a lot more accuracy checking, but also if we needed a technology that would, say, paralyze somebody but not hurt them forever, I was brainstorming the different tools and technologies that could be highlighted.

We also decided to do a longer feature of the work that we do in our lab. Sometimes, when you want to make something super cool and exciting to read, you're depicting technologies five or 10 years from now, right? So we also wanted to give folks something that's happening in labs right now, and that people might be like, "Wow, I would have thought that that didn't exist yet." 

We wanted to show myself, as well as the women working with me in my lab and the kinds of things that they do. It was really cool to be able to highlight some real students at MIT in the context of the Curie Society.

AM: How does it feel to be immortalized in comic book form?

RR: I'm living in the dream, really. I've always wanted to write and contribute to the world of fiction, but when I write for work, I'm a scientist, I write a very specific plan of how to get a grant funded in the next five years that will do exactly this and this. There's creativity in there, but it's creativity within very strict constraints, and I think the opportunity to release those constraints a little bit and still scratch that creative part of my brain, while talking about the science…. It's very cool, I'm very happy about it.

AM: That creative process is pretty important, and obviously the book is crammed with science. As the advisor to the story, how far can you push the science from fact to fiction?

RR: That's an interesting question, particularly because there are probably different aspects of science that I treat differently in that way. I mean one of the things about being a PhD trained scientist and working in a lab is that I know about some very niche areas, but then I also have a degree in mechanical and aerospace engineering. But it's not like I can really comment too deeply on some of the work on airfoil design for planes, which showed up in one of the books.

I sometimes feel like I'm hypercritical of the things that are closer to my work related to genetic engineering or making new tissues by 3D printing — that sort of stuff that I know a lot about. So the first thing I do is try to modulate. For things that are not directly in my area of expertise, I think I'm able to give a lot more freedom — if this passes the smell test or it doesn't defy or fundamentally break the laws of physics, it's good. Maybe it's not exactly perfectly right, but it's a story and that's OK. With stuff that is more related to the things that I do, I have to first try to censor myself a little bit more.

So I try to first turn off that part of my brain, but I think now that we've worked together for many years the team hopefully feels comfortable being like, "Hey, this is the reason we wanted to say it that way. If you feel this is fundamentally wrong, is there something else we could say that would still move the story from point A to point B?" 

I think particularly being involved in an earlier draft is great, because then before they've committed too much to something, I can figure out how to best lead science into that. I think just having a good relationship with the authors over many years has helped.

AM: It must have been fun actually being able to explore other areas of science that you're not an expert in. Did you learn a lot from researching the story as well?

RR: Yeah, I mean, I'm not incentivized in my job to think outside of the exact context of what my lab works on because I'm paid to be an expert. Zooming back out and being a generalist sparks your own enthusiasm for the things that you thought were cool when you were a kid. I really wanted to go into aerospace and make rockets, and I still think those things are exciting, but it's not what I'm doing right now. 

You can't do everything, but I think that some of the technologies, in particular related to energy and the climate crisis, are very exciting. Even though a lot of my work is focused on human health — which is great and very motivating — sometimes, as a human being living on the planet, you're also thinking more broadly about other grand challenges that are facing us. So catching up on what everyone else is doing is very heartening and exciting to see.

AM: How effective do you think graphic novels are in getting people into STEM.

RR: One of the things that I think is very important is make sure we're meeting people where they are. Some people respond really well to the written word, some people respond well to digital media, some people would prefer everything to be delivered to them in the form of a dance — and that's OK. Usually most people are a combination of those things and you need to hear stuff repeated three or four different times for it to really sink in.

I think graphic novels fit in a nice space. We have TV shows where people describe science for kids of different audiences, and there's a lot of YouTube videos that do that. Science fiction novels also do a job of exploring that space, but they often seem to target older audiences and really focus on dystopian visions of the future.

So when you're thinking about this audience, how do you introduce realistic science fiction in a visually compelling way, that has a narrative and also highlights several different kinds of people? You could certainly do it through superhero movies, but [graphic novels] are another way of doing it that I think could actually reach a ton of people, and can be something they revisit over time. Maybe it's in their bookshelf and they look at it but can't understand it the first time; then they go and they learn something in school and they can come back and go to that page.

I think it's one part of the arsenal, which doesn't have a ton of things in it right now, but there's a big opportunity for us to reach a lot of people who would not otherwise see these kinds of stories.

AM: The book itself has a very diverse cast of characters and is obviously focused on getting more women into STEM. From your perspective, is science doing enough to make this positive change, and what more could we be doing?

RR: I think as long as society is evolving we're always playing catch up in any discipline to make sure that we're capturing whatever the current distribution of the population is. I think in science, for example, we have made tremendous progress in recruiting more women into undergraduate programs — certainly at MIT we've had 50% women in our undergraduate programs for many years, which is lovely — but as you go farther along, certainly in graduate school, in the professoriate, in the leadership of STEM businesses, the representation, at least of women and certainly people that match different aspects of diversity, it's still very low. 

One of the things I really like about the way the Curie Society structures its characters is that even though the protagonists are younger, there are a lot of older female scientists that are portrayed as really senior people in the books. I think that's very important because they pretty openly acknowledge that the world they faced was fairly different to what these younger girls are facing, and that interplay has been really nice to see. I haven't really seen that in other media or other stories.

I do think that despite inroads in getting more people excited about science, when I interact with middle schoolers, and teenage girls in particular, there is still a lot of hesitation and a lack of self-belief about the role that they can play in science. I don't think it's something that we can pat ourselves on the back and say, "This is a solved problem, we don't need to worry about this anymore." We're combating thousands of years of all of us having certain beliefs about who's capable of what, so I think we still have some work to do there, at least to keep the pipeline going. 

But we also have to recognize that just getting a bunch of 12-year-olds excited about science is not enough. You need to actually preserve and promote and retain that enthusiasm throughout their lives, and that's a much longer scale problem.

AM: Do you think there are any particular challenges to getting younger people, particularly young girls, into science? Is there anything we can do?

RR: One threat that I see right now is that it's wonderful to highlight women and young girls that are excited about science, but if those are the only people in the story, you're sort of removing them from a natural context or the fact that we live in a very gender-diverse society. I would love to see more male characters interacting with these female scientists in respectful ways.

I think we need to be very careful of not just telling young women to pursue science, but also educating young men that, "Did you know that there are women who do science and are very good at it and we can all play together and do cool things?" 

More broadly, making sure our interventions are not just targeted at people who identify as girls is the missing gap in the field that we can keep pushing toward.

AM: So essentially what we need to do is see more people who are in the science environment in front of people talking about what we're doing?

RR: Yeah, and get more young boys to read these books too. I just think about the number of books I read as a kid that featured young boys and I still learned a lot from them. I would love for it to go the other way. Yes the story is about women and I hope young girls like it, but I hope a lot of boys read it too and think that it's an exciting story and something to emulate.

AM: Finally, if you were a character in the book, what would your specialized skill be? If you're already a member of the Curie Society and are keeping it secret, that's fine…

RR: One of the things I always wish I could do — particularly because we in my lab are always building little tissues and models of the human body and then trying to understand what happens inside the human body — is being able to go inside a person and see exactly what's going wrong. I think probably being able to see, at very high resolution, how cells are talking to each other and how we can manipulate that, that would probably be the secret skill — but you'll never know, I'll never tell.

According to Leslie Dobson, a clinical and forensic psychologist, there are a number of reasons why someone may feel as if they are being watched. These causes span a broad spectrum, including exposure to scary books, movies or news; hypervigilance following a stressful or traumatic event; and serious mental health conditions.

"In more extreme cases, a person may experience paranoia and hypervigilance, often related to an underlying mental health condition or physical brain ailment," Dobson said in a written message.

Of course, sometimes we really are being watched. People likely evolved to be sensitive to another person's gaze, and it's been suggested the human brain has a neural network dedicated solely to processing gaze, according to an article written by Harriet Dempsey-Jones, a postdoctoral research fellow in cognitive neurosciences at The University of Queensland in Australia. It's possible that our attentiveness to gaze arose because it can support cooperative interactions between humans. This ability usually isn't difficult to master; it's fairly easy to see where a person is looking because we can see where their pupils are focused, and with our peripheral vision we can pick on cues, such as body language, indicating that a person is looking at us.

But sometimes, even if no one is watching, outside stimuli can make us feel afraid and look around to see if we're being watched. This could include watching or reading a thriller in which a protagonist is being stalked by a threatening figure, or hearing a random noise when home alone.

Related: Why do people dissociate during traumatic events?

For people who have experienced traumatic events, hypervigilance becomes a defense mechanism that is meant to prevent us from experiencing future stress by avoiding danger, according to a 2023 study in the journal Frontiers in Psychology. Symptoms like paranoia and anxiety that usually come after stressful events can occur in a similar region of the brain, Dobson explained.

"The amygdala processes our emotions such as stress and anxiety," she told Live Science. "If it is overactive or harmed from physical damage or ongoing trauma stressors, it may lead to heightened emotional responses such as perceiving threat."

It's not uncommon for people to feel watched, Dr. Alice Feller, a clinical psychiatrist based in California, told Live Science. So how do you distinguish reasonable caution from a more serious issue?

The problem arises when someone constantly feels watched or paranoid about being watched for a long period of time.

"[With] mental illness, what happens is you lose that ability to wonder if it's just a feeling, you know, you kind of lose insight into your own bodily and mental process," Feller said. "You can do a reality check, but it doesn't necessarily stick."

For example, symptoms of schizophrenia include hypervigilance and paranoia, which can include the delusion that someone is watching you. Research suggests that in people with schizophrenia, paranoia is associated with abnormal activity in the limbic system, a part of the brain that includes the amygdala and controls our emotional and survival-based behavioral responses, such as the fight-or-flight response.

A 2022 study explained that in patients with schizophrenia, paranoia has been associated with increased blood flow during resting state in the amygdala. Moreover, unusual connectivity between the amygdala and other areas of the brain, such as the visual cortex, hippocampus and the prefrontal cortex, has been linked with paranoia, suggesting that "current paranoia is linked to aberrant connectivity within the core limbic circuit" suggesting "amplified threat processing and impaired emotion regulation."

Regardless of the cause, Feller and Dobson both said that it's worth seeking mental health support if you experience persistent paranoia. This is especially true if the feeling of being watched happens despite physical evidence that no one else is there, or if the anxiety of being watched becomes worse.

"I encourage people to seek mental and medical intervention when they begin to notice they are struggling, rather than trying to wait it out," Dobson said. "Early intervention is key. If a person is struggling more days a week than not, or if their job, education, or relationships are beginning to struggle, it is important to seek out a professional."

This article is for informational purposes only and is not meant to offer medical advice.

"Unfortunately, we can't ask a baby exactly why they're rubbing their eyes," Dr. Rebecca Dudovitz, an associate professor of general pediatrics at the UCLA David Geffen School of Medicine, told Live Science.

"But we do know from human experience that people do tend to rub their eyes when they're tired, and we think it may have to do with just a feeling of discomfort that you get when your eye muscles have been working hard and it's time for a break," Dudovitz said.

The same way your shoulders might need a massage after you sit at a desk all day, the muscles that help your eyes focus feel better after you rub them. Babies spend a lot of their time staring at objects in their environment, and their eyes get tired.

Related: What happens when a baby takes its first breath?

Staring also dries out the eyes — and considering that babies blink only a few times a minute, it shouldn't be surprising that their eyes get dry, too.

"Tears are not just salt water, but mucus near the surface, salt water in the middle, and a layer of oil from the eyelid meibomian glands to prevent evaporation," Dr. Robert W. Arnold, an ophthalmologist at Alaska Children's Eye & Strabismus, told Live Science via email. "Therefore, a healthy tear is a tri-layer. That tri-layer must be renewed and spread over the surface smoothly by blinking."

When we're faced with too much intense visual attention, we don't blink enough. And without enough blinking, that tri-layer can break apart and leave dry patches on the surface of the cornea, the outer, clear part of the eye that covers the iris and pupil. When that happens, eye rubbing may just be a reminder to blink more.

"This is similar to breathing, the rate of which is usually automatic, and sufficient. However, when we are distracted or tired, we may not breathe often, or deep enough," Arnold said. "Therefore, we sigh. Eye rubbing in children may be akin to sighing for eyeball health."

Rubbing your eyes isn't particularly good for you, however. Excessive eye rubbing can lead to vision problems.

One commonly cited reason it feels good to rub your eyes when you're tired is that it reduces blood pressure by stimulating the trigeminal and vagus nerves, which run from the brain to the eyes and from the brain throughout the body, respectively. In some people, this can reduce heart rate by more than 20% in a phenomenon known as the oculocardiac reflex.

But Arnold questions this reasoning. "There is no obvious reason why a kid would feel better with a slow heart rate," he said.

In fact, the oculocardiac reflex can have life-threatening results, including bradycardia — a heart rate below 60 beats per minute — and cardiac arrest.

"We don't think purposeful stimulation of the oculocardiac reflex is a reason for children rubbing the eyes, but it could be a result of excessive rubbing of the eyes," Arnold said.

But most likely, babies rub their eyes for the same reasons adults do: Their eyes are tired and dry, and they're ready for a nap.

In short, dissociation can be useful for situations in which someone can't physically get away from stress or danger, such as being the victim of a violent crime or abuse, said Steven Dubovsky, a professor emeritus of psychiatry at the University at Buffalo in New York.

Typically, the sympathetic nervous system — which is responsible for our "fight or flight" response — activates when a person is in imminent physical danger. Mammals, including humans, evolved to have this response, as it pushes them to survive by fighting or fleeing from danger. Dissociation is another way the nervous system is primed to respond to trauma when fight or flight appears to be too dangerous or impossible. Dubovsky described a scenario in which someone could be followed and attacked by a group of people on a dark street. If a person can't find a way to escape or fight back, they might find themselves stuck in the situation.

"When the stressful thing is something you can't escape from, you're going to have trouble functioning unless you can turn [the fear] down," he told Live Science.

Dissociation can protect someone in the moment so that they are mentally separated from a situation causing physical pain, emotional pain or both. This coping strategy may also be associated with freezing and separating the person from the memory of the traumatic event, according to a 2017 study in the journal Current Psychiatry Reports. Oftentimes, victims of abuse or sexual assault report dissociation during the event, a 2015 study in the journal Medicine outlined. Some people report having foggy memories of an event after the fact due to dissociation. Though the lack of clear memory or lack of feeling attached may be jarring after the fact, the dissociation can stop someone from having to relieve painful memories, Dubovsky said.

Related: Is it possible to avoid unwanted thoughts?

Ruth Ellingsen, an associate clinical professor of psychology at the University of Oregon, reiterated that for some people, dissociation may be the only way to stay safe when experiencing abuse. "There's also times when trying to flee a situation could result in more hurt," Ellingsen told Live Science. "For example, if you're a child being abused, [flight] could potentially make the abuse even worse."

In scenarios like this, freezing and disconnecting do more than emotionally separate someone from the stress; this response may be the best decision for survival.

Problems can arise if people continue to dissociate even once they are separated from the intense trauma, as opposed to relying on other coping mechanisms, such as mindfulness, meditation or help from a professional, Ellingsen said.

Both Dubovsky and Ellingsen explained that people who continue to dissociate often struggle with daily stress, like meeting work deadlines or speaking with their peers. Many feel detached in their relationships and may find themselves distracted during what used to be usual interactions or tasks. It's possible that because the disconnection from the traumatic event kept them "safe" or at least detached from bad memories, this coping mechanism becomes the default for other forms of stress, Ellingsen said.

"We tend to see this [overreliance on dissociation] when regular coping resources are depleted," she said. "If you're dissociating a lot when you're encountering stress, that is indicating that maybe you don't have more healthy coping strategies that are working for you."

But the goal of addressing chronic dissociation isn't to eliminate it. After all, it can be a useful tactic to help survive a dangerous situation. But memories of the traumatic event are often disruptive and painful, so having some distance from that could mean a better quality of life after the trauma, Dubovsky said.

Before diving into this question, it's important to know that the medical definition of psychopathy is incredibly complicated, and experts are still debating what this term should encompass. "Psychopathy is not a diagnosis in itself," Katarina Howner, a neuroscientist at the Karolinska Institute in Sweden, told Live Science. "It's a personality disorder with really close connections to antisocial and criminal behavior."

Like other personality disorders, this condition is identified through life history interviews in which psychiatric professionals probe every aspect of an individual's life, looking for patterns of psychopathic traits, such as callousness and quickly-triggered aggression. Affected individuals are at particularly high risk of committing violent crimes or reoffending after release from prison.

"People with psychopathic traits are really focused on themselves and their own needs," Howner explained. "They have a lack of empathy and they don't experience feelings of shame or guilt. There's a grandiosity and impulsivity which means they think that they can do anything without consequence."

However, this doesn't mean people with psychopathy don't have any empathy at all, Howner said. Psychologists break this complex emotion down into several different sub categories.

"Affective or emotional empathy is where you feel the emotions that others are showing. You have a kind of emotional resonance with the other person, and this is something psychopaths struggle with," she said. "But cognitive empathy is more like mentalization. That is, you can think how another person is thinking or feeling. Psychopaths are usually good at this and use it to manipulate people."

Related: Are humans inherently violent?

This apparent lack of emotional empathy is what makes psychopathic individuals seem cold and cruel. However, studies consistently show people with psychopathy have the capacity to experience this type of empathy under the right conditions. "When you deliberately focus people with psychopathy on labeling an emotion in a photograph in an unambiguous way (meaning the face is showing 100% of that emotion), they can do that accurately," Arielle Baskin-Sommers, a psychologist at Yale University told Live Science. "If you flash the faces really quickly or blend the emotions, then people with psychopathy seem to struggle." The difficulty, she said, is not that psychopaths lack this empathy but that they lack the natural ability to do it easily.

But is this a skill that psychopaths can learn? There's every reason to believe so, Baskin-Sommers told Live Science. That they can experience empathy and that this ability seems to change depending on the situation is a promising sign. 

So why does this behavior develop in the first place? Scientists aren't exactly sure, although evidence suggests it's a mixture of genetic and environmental factors. But while the cause is unknown, psychopathy's effect on the brain is well-established.

Studies have shown profound differences in both the structure of the brain and how different brain regions communicate in psychopathic individuals.

"The size of the structure and function of the amygdala, which is a region of the brain important for our emotional processing, reliably shows up as different in people with psychopathy," Baskin-Sommers said. "We also tend to see differences in prefrontal structures of the brain that have to do with general cognition and control of behavior. People with psychopathy fundamentally have very different brains." These neurological differences mean that psychopathic individuals don't process emotions in the same way as individuals without psychopathy do and this physical disparity is difficult to overcome.

Current treatments rely on a combination of approaches including cognitive behavioral therapy and medication, but there's no simple cure to help psychopathic individuals easily experience empathy. Strategies focusing on rewarding good behaviors have shown some success in helping patients adapt to society and both Howner and Baskin-Sommers said that this should be the focus of interventions, rather than developing empathy.

"Current data suggest that psychopathy is no more or less untreatable than any other psychiatric disorder," Baskin-Sommers said. "There's been an unfortunate narrative about psychopathy that these people are fundamentally evil, but society needs to realize that this is a condition that deserves support and necessitates treatment."

The dawn of a new year marks a fresh start and motivates many people to break bad habits. Some are easier to shake than others, however, and the tendency to procrastinate is among the stickiest.

Whether it's finishing a piece of work, sending an email or going for a run, some tasks can feel insurmountable. The easiest way to avoid these tasks is to put them off until later or to never complete them at all. But why do people procrastinate, and is there anything we can do to reduce this tendency? 

"At its heart, procrastination is about avoidance," Fuschia Sirois, a professor of psychology at the University of Durham in the U.K., told Live Science. Rather than the task itself, however, it's often the emotions attached to an activity that cause people to recoil, she said. 

Tackling the first lines of a college essay may bring up feelings of self-doubt, for example. When you're faced with a broad question or topic to write about, the lack of clear instructions can trigger a fear of not getting it right or of what might happen if you get it wrong, Sirois said.

Related: Do New Year's resolutions really work?

Procrastination is a specific form of delay that is both unnecessary and voluntary, meaning it isn't caused by the person's need to prioritize other tasks or by an unforeseen emergency, Sirois said. The person procrastinating usually does so despite knowing that the task is important or valuable to them or others, and that putting it off could be detrimental to them or others, she added.

Chronic procrastinators typically struggle to manage and regulate their emotions, Sirois said. In a 2021 brain imaging study, Sirois and her colleagues found that college students with a higher volume of gray matter in the left dorsolateral prefrontal cortex — a region of the brain associated with self-control — were less prone to procrastination than their peers were. The more neural connections there were between this part of the brain and the frontal regions, the better the students were at regulating negative emotions, focusing on long-term benefits and sticking with tasks. Those with fewer connections between those areas were more likely to procrastinate at the cost of future rewards, the researchers concluded.

Difficulties in emotion regulation partly explain why people with attention-deficit/hyperactivity disorder (ADHD) are more likely to procrastinate.

A 2018 study also showed that the threat detection center of the brain, the amygdala, tends to be larger, and therefore more sensitive, in people who procrastinate. "The threat can be something tiny," Sirois said — how to word an email, for example. But the anticipated discomfort may be strong, so the urge to avoid discomfort may override any considerations of the consequences of not completing the task.

The fewer connections that existed between the amygdala and another region of the brain called the dorsal anterior cingulate cortex, which determines how we react to perceived threats, the more likely people were to put things off, according to the study.

"Like any personality trait, there are some biological underpinnings," Sirois said. Research suggests that procrastination is linked to impulsivity on a genetic level and may be a heritable trait. Sirois agreed that "there can be some genetic underpinnings, but that doesn't mean you're stuck and that's who you are."

Environmental factors are just as important in shaping our response to aversive tasks, Sirois said. Someone who doesn't usually procrastinate can do so if they find themselves in a situation that depletes their coping resources over a long period of time, such as the death of a family member.

"Procrastination becomes a quick, easy and 'dirty' way of coping with something, albeit in an avoidant way, when your coping resources are maxed out," Sirois said. But procrastination can pile on more stress by leaving a task hanging over a person's head, thus triggering a vicious cycle that can damage mental health, lower academic performance and lead to financial distress. 

Luckily for those of us who drag our feet — it took the author of this article eight months to start writing it — research has shown that learning to manage negative emotions can help reduce procrastination. Sirois recommended taking a step back when a task feels overwhelming to assess what emotions the situation has triggered and why you wish to avoid them. In the case of a college essay or work assignment, it may help to clarify any uncertainties about what the task actually is or to break it down into smaller tasks, Sirois said. Finding something meaningful about the task and rewarding yourself for finishing it might also be helpful, she added.

But if this is the year you want to stop procrastinating, let your resolution be to exercise self-compassion. "Forgiveness for your procrastination is very effective in reducing subsequent procrastination," Sirois said.

Leap years are years with 366 calendar days instead of the normal 365. They happen every fourth year in the Gregorian calendar — the calendar used by the majority of the world. The extra day, known as a leap day, is Feb. 29, which does not exist in non-leap years. Every year that is divisible by four, such as 2020 and 2024, is a leap year except for some centenary years, or years that end in 00, such as 1900. (We'll explain why further down.)   

The name "leap" comes from the fact that from March onward, each date of a leap year moves forward by an extra day from the previous year. For example, March 1, 2027 will be a Monday but in the next leap year, 2028, it will fall on a Wednesday. (Normally, the same date only moves forward by a single day between consecutive years.) 

Related: Earth's core wobbles every 8.5 years, new study suggests

Other calendars, including the Hebrew calendar, Islamic calendar, Chinese calendar and Ethiopian calendar, also have versions of leap years, but these years don't all come every four years and often occur in different years than those in the Gregorian calendar. Some calendars also have multiple leap days or even shortened leap months.

In addition to leap years and leap days, the Gregorian calendar also has a handful of leap seconds, which have sporadically been added to certain years — most recently in 2012, 2015 and 2016. However, the International Bureau of Weights and Measures (IBWM), the organization responsible for global timekeeping, will abolish leap seconds from 2035 onward.

Why do we need leap years? 

On the face of it, all of this "leaping" may seem like a silly idea. But leap years are very important, and without them our years would eventually look very different. 

Leap years exist because a single year in the Gregorian calendar is slightly shorter than a solar, or tropical, year — the amount of time it takes for Earth to completely orbit the sun once. A calendar year is exactly 365 days long, but a solar year is roughly 365.24 days long, or 365 days, 5 hours, 48 minutes and 56 seconds. 

If we did not account for this difference, then for each year that passes the gap between the start of a calendar year and a solar year would widen by 5 hours, 48 minutes and 56 seconds. Over time, this would shift the timing of the seasons. For example, if we stopped using leap years, then in around 700 years the Northern Hemisphere's summer would begin in December instead of June, according to the National Air and Space Museum.

Related: How many times has Earth orbited the sun?

Adding leap days every fourth year largely removes this problem because an extra day is around the same length as the difference that accumulates during this time. 

However, the system is not perfect: We gain around 44 extra minutes every four years, or a day every 129 years. To solve this problem, we skip the leap years every centenary year except for those that are divisible by 400, such as 1600 and 2000. But even then, there is still a tiny difference between calendar years and solar years, which is why the IBWM have experimented with leap seconds. 

But overall, leap years mean that the Gregorian calendar stays in sync with our journey around the sun.

When was the last leap year? When is the next leap year?

The history of leap years 

The idea of leap years dates back to 45 B.C. when the Ancient Roman emperor Julius Caesar instituted the Julian calendar, which was made up of 365 days separated into the 12 months we still use in the Gregorian calendar. (July and August were originally named Quintilis and Sextilis respectively but were later renamed after Julius Caesar and his successor Augustus.)

The Julian calendar included leap years every four years without exception and was synced up to Earth's seasons thanks to the "final year of confusion" in 46 B.C., which included 15 months totaling 445 days, according to the University of Houston.

For centuries, it appeared that the Julian calendar worked perfectly. But by the mid-16th century, astronomers noticed that the seasons were beginning around 10 days earlier than expected when important holidays, such as Easter, no longer matched up with specific events, such as the vernal, or spring, equinox.

To remedy this, Pope Gregory XIII introduced the Gregorian calendar in 1582, which is the same as the Julian calendar but with the exclusion of leap years for most centenary years (as outlined above). 

For centuries, the Gregorian calendar was only used by Catholic countries, such as Italy and Spain, but it was eventually adopted by Protestant countries, such as Great Britain in 1752, when their years began to greatly deviate from Catholic countries. 

Because of the discrepancy between calendars, countries that later switched to the Gregorian calendar had to skip days to sync up with the rest of the world. For example, when Britain swapped calendars in 1752, Sept. 2 was followed by Sept. 14, according to the Royal Museums Greenwich. 

At some point in the distant future, the Gregorian calendar may have to be re-evaluated as it slips out of sync with solar years. But it will take thousands of years for this to happen. 

Why is leap day on Feb. 29?

In the eighth century B.C., the Roman calendar had just 10 months, beginning in March and ending in December. The cold winter season was ignored, with no months to signify it. But this calendar had only 304 days, so January and February were eventually added to the end of the religious year. As the last month, February had the fewest days. But Romans soon began associating these months with the start of the civil year, and by around 450 B.C., January was viewed as the first month of the new year.

When Pope Gregory XIII added the leap day to the Gregorian calendar in 1582, he chose February because it was the shortest month, making it one day longer on leap years.

There are stories you expect to ruffle some feathers — we're looking at you, aliens — and then there are the ones we never thought would kick up a storm. This year, scientists surprised us with claims of successful room temperature superconductivity, reported sightings of long-extinct species and alternative theories to the origin of humankind. We've not missed out on juicy UFO content either, so without further ado, here's our pick of the most controversial science stories in 2023. 

UFO and 'alien mummy' Congress hearings 

In May, Congress held its first public hearing on UFOs since the 1960s to discuss 144 reported sightings of mysterious objects. During the hearings, two military officials were questioned about their knowledge of the unexplained phenomena. The May hearing was followed by another in July, in which three military witnesses claimed evidence of non-human technologies was being hidden from the public. All three witnesses said it's possible unidentified anomalous phenomena (UAP) are being launched by aliens interested in America's nuclear capabilities, testing for weaknesses in U.S. air defense systems or conducting reconnaissance in American airspace.

Related: 20 of the best conspiracy theories

Mexico had its own extraterrestrial matters to deal with, after a journalist unveiled two "alien" bodies before the country's congress in September. Together with a military medical doctor, the journalist, Jaime Maussan, claimed that DNA tests showed the bodies were non-human but not necessarily extraterrestrial. Scientists rallied to refute these claims and debunk them.

'Anomalous' metal spheres 

This year, a prominent Harvard astrophysicist claimed that more than 50 "anomalous" metal spheres pulled from the Pacific Ocean could be the work of intelligent aliens. Avi Loeb claimed the tiny pellets likely fell into the ocean in 2014, when a fireball shot across the sky above Papua New Guinea. Loeb argued the blazing object could be a relic from another star system and might harbor traces of alien technology.

In November, several studies found that the metal spheres are more likely a by-product of burning coal and therefore probably come from industrial pollution on Earth. Loeb refuted these results in a blog post on Nov. 15. He argued that coal is non-magnetic and could not have been picked up by the instruments he used to dredge the pellets from the ocean. He noted that 93% of the collected samples have not yet been analyzed and cautioned that scientists should not jump to conclusions. 

Tasmanian tigers prowling the wilderness 

Based on reported sightings since 1910, researchers suggested in March that Tasmanian tigers (Thylacinus cynocephalus) survived in the wild until the 1980s and may still be prowling the Tasmanian wilderness today. These marsupials were thought to have gone extinct in 1936, when the last known Tasmanian tiger died in captivity, but the researchers estimated the earliest date for extinction was in the mid-1950s — that is, if the species did go extinct.

However, the study was met with skepticism, as the findings were based solely on reported sightings of Tasmanian tigers. No carcass was ever found to suggest the species persisted in the wild, experts told Live Science, and the resemblance between Tasmanian tigers and dogs means people who reported sightings could easily have been mistaken.

Contentious Brazilian dinosaur fossils 

In May, paleontologists criticized a team of researchers in Europe after they published a study on 115 million-year-old dinosaur fossils that had been unearthed by commercial diggers in Brazil then sold and shipped to Germany. The specimens belong to a carnivorous species related to Spinosaurus known as Irritator challengeri, which the new study suggests scooped up prey like a pelican.

The study authors thought the fossils legally belonged to Germany, as they arrived there before 1990, after which time Brazil began restricting scientific exports to other countries. But an older 1942 law states that Brazilian fossils are federal property and cannot be sold, meaning the fossils may have been stolen. Paleontologists, including the authors, agreed the fossils should be returned to Brazil.

Semiconductor furore 

This summer, researchers in South Korea claimed they made a superconductor at room temperatures and pressures, sparking a flurry of attempts to replicate the results. If verifiable, the discovery of a material able to carry electricity in everyday temperatures and without electrical resistance would open new technological windows.

But other experts cautioned the published work was sloppy and not peer-reviewed. When they tried to replicate the findings, none of the materials they created yielded identical results to LK-99, the South Korean team's superconductor. Subsequent publicized attempts have also proven unsuccessful. Regardless of the outcome for LK-99, the announcement gave rise to meaningful discussions on social media and elsewhere about an area of science unfamiliar to the general public. 

Hominin fossils in space 

In September, a Virgin Galactic space flight took off from Earth with priceless and extremely contentious cargo: the fragmentary remains of two of our ancient relatives, Australopithecus sediba and Homo naledi. South African-born billionaire Timothy Nash carried the hominin fossils to the edge of space in a cigar-shaped tube, causing an uproar in the scientific community.

Related: NASA may have unknowingly found and killed alien life on Mars 50 years ago, scientist claims 

The permit to take the fossils on the flight, which was approved by the South African Heritage Resources Agency, said the goal of the mission was to promote science and bring global recognition to human origins research in South Africa. But experts criticized the undertaking because it lacked a scientific purpose, especially as a malfunction could have destroyed the fossils. Critics also noted the trip raised ethical issues surrounding the respect for human ancestral remains and tainted the image of paleoanthropological research.

Antarctica's ozone hole 

A study that claimed the ozone hole above Antarctica is not recovering as fast as we thought and could be getting bigger came under fire in November, with experts criticizing the methodology and accusing the authors of cherry-picking data.

The conclusion that the concentration of ozone at the center of Antarctica's ozone hole decreased by 26% between 2001 and 2022 omitted several factors — including three consecutive years of La Niña from 2020 to 2022, massive wildfires that raged in Australia during 2020 and water vapor from Tonga's huge eruption in 2022 — that would explain why the past few years have been unusual, experts told Live Science. Experts also questioned the authors' decision to exclude two years' worth of data, which they argued would have skewed the results.

Overall, experts said, the results were unrealistic and useless to infer much about global ozone recovery trends. 

Alternative origin story 

A newly identified ape fossil from an 8.7 million-year-old site in Turkey led scientists to posit that hominines — a group that includes humans, the African apes and their fossil ancestors (and different from hominins, which comprise species belonging to the human lineage after it diverged from the ancestors of chimpanzees and bonobos) — first evolved in Europe. This deviates from the conventional view that hominines originated exclusively in Africa and suggests members of this group dispersed to Africa from the Mediterranean instead.

But paleontologists pointed out that comprehensive analyses of great ape and early human relative fossils do not support this argument. It's also possible that the newfound species, Anadoluvius turkae, migrated to the Mediterranean from Africa after evolving there, rather than the other way round, experts told Live Science. Fossils like these are sparse in the African fossil record, and while that doesn't mean hominines weren't there, it does raise questions about where the group first evolved, they added. 

Netflix documentary under scrutiny 

Homo naledi — an ancient human relative that lived about 300,000 years ago — became a lightning rod for controversy earlier this year after a research team claimed the extinct hominins deliberately buried their dead and engraved rocks. These complex behaviors, for which there was "no convincing scientific evidence," were featured in the hit Netflix documentary "Unknown: Cave of Bones" (2023), which was released just days after the claims were published in the journal eLife.

Related: Early human relatives purposefully crafted stones into spheres 1.4 million years ago, study claims 

The findings could be substantiated one day, experts told Live Science, but there is currently no strong evidence to support the idea that hominins with orange-size brains could perform behaviors only known in species with much larger brains, such as modern humans. The team behind the claims responded to reviewers' comments, but it's unlikely their words will be the last in this debate.

'Curse tablet' or fishing weight? 

A postage stamp-size piece of lead was discovered in the West Bank in 2019, and this year, some researchers found that it carried the earliest-known inscription of the name of the Israelite god Yahweh. The authors of the original paper called the artifact a "curse tablet," based on their interpretation of the markings as calling on Yahweh to curse his enemies. But others are not convinced, because they think it shows no words and might actually be a fishing weight.

The controversial lead tablet bore no inscriptions on the inside, critics told Live Science, just indentations caused by weathering. The tablet closely resembles weights commonly used for fishing or birding nets during the time the tablet was dated to, between 1400 and 1200 B.C.

The original researchers responded to critics by saying they are confident there is writing on the tablet and are working on a second paper detailing inscriptions on the folded tablet's exterior.