I tried not to panic. I was floating effortlessly in a pitch-black tank filled with salty, skin-temperature water, wearing earplugs and nothing else. Within minutes I could no longer feel the sponge in my ears or smell the musty scent of water. There was no light, no smell, no touch and - save for the gasping of my breath and drumming of my heart - no sound.

I was trying out North America's avant garde drug: sensory deprivation. Across the continent "float houses" are increasing in popularity, offering eager psychonauts a chance to explore this unique state of mind. Those running the business are quick to list the health benefits of frequent "floats", which range from the believable - relaxation, heightened senses, pain management - to the seemingly nonsensical ("deautomatization", whatever that means). Are these proclaimed benefits backed up by science or are they simply new-age hogwash?

A Sordid (and Sensationalized) History

Why would anyone willingly subject him or herself to sensory deprivation? You've probably heard the horror stories: the Chinese using restricted stimulation to "brainwash" prisoners of war during the Korean War; prisons employing solitary confinement as psychological torture. Initial research studies into the psychophysical effects of sensory deprivation, carried out in the 1950s at McGill University, further damaged its reputation, reporting slower cognitive processing, hallucinations, mood swings and anxiety attacks among the participants. Some researchers even considered sensory deprivation an experimental model of psychosis.

We think of psychopaths as killers, alien, outside society. But, says the scientist who has spent his life studying them, you could have one for a colleague, a friend - or a spouse

There are a few things we take for granted in social interactions with people. We presume that we see the world in roughly the same way, that we all know certain basic facts, that words mean the same things to you as they do to me. And we assume that we have pretty similar ideas of right and wrong.

But for a small - but not that small - subset of the population, things are very different. These people lack remorse and empathy and feel emotion only shallowly. In extreme cases, they might not care whether you live or die. These people are called psychopaths. Some of them are violent criminals, murderers. But by no means all.

Professor Robert Hare is a criminal psychologist, and the creator of the PCL-R, a psychological assessment used to determine whether someone is a psychopath. For decades, he has studied people with psychopathy, and worked with them, in prisons and elsewhere. "It stuns me, as much as it did when I started 40 years ago, that it is possible to have people who are so emotionally disconnected that they can function as if other people are objects to be manipulated and destroyed without any concern," he says.

The view that the Mafia is an organization of especially ruthless psychopaths is wrong - in fact, members of 'Cosa Nostra' have lower psychopathic traits than other criminals.

That's according to a new study from Italian researchers Schimmenti and colleagues, who, appropriately enough, are based in Sicily, the Mafia's birthplace.

Schimmenti et al went to a prison in Palermo, Sicily, and interviewed 30 convicted Mafia members:

Seven of the Mafia members (23%) had been convicted of murder, 17 (57%) for other violent offenses, and the remainder for crimes including trafficking in narcotics, extortion, fraud, sexual exploitation and kidnapping...

They compared them to a comparison group of 39 prisoners from the same jail, whose crimes were not gang-related. Their offenses included murder, rape, child sexual abuse and armed robbery.

In captivity, grey parrots are often kept in social isolation, which can have detrimental effects on their health and well-being. So far there have not been any studies on the effects of long term social isolation from conspecifics on cellular aging.

Telomeres shorten with each cell division, and once a critical length is reached, cells are unable to divide further (a stage known as 'replicative senescence'). Although cellular senescence is a useful mechanism to eliminate worn-out cells, it appears to contribute to aging and mortality. Several studies suggest that telomere shortening is accelerated by stress, but until now, no studies have examined the effects of social isolation on telomere shortening.

Cognitive scientist and philosopher Daniel Dennett is one of America's foremost thinkers. In this extract from his new book, he reveals some of the lessons life has taught him

1. Use your mistakes

We have all heard the forlorn refrain: "Well, it seemed like a good idea at the time!" This phrase has come to stand for the rueful reflection of an idiot, a sign of stupidity, but in fact we should appreciate it as a pillar of wisdom. Any being, any agent, who can truly say: "Well, it seemed like a good idea at the time!" is standing on the threshold of brilliance. We human beings pride ourselves on our intelligence, and one of its hallmarks is that we can remember our previous thinking and reflect on it - on how it seemed, on why it was tempting in the first place and then about what went wrong. I know of no evidence to suggest that any other species on the planet can actually think this thought. If they could, they would be almost as smart as we are. So when you make a mistake, you should learn to take a deep breath, grit your teeth and then examine your own recollections of the mistake as ruthlessly and as dispassionately as you can manage. It's not easy. The natural human reaction to making a mistake is embarrassment and anger (we are never angrier than when we are angry at ourselves) and you have to work hard to overcome these emotional reactions.

Try to acquire the weird practice of savouring your mistakes, delighting in uncovering the strange quirks that led you astray. Then, once you have sucked out all the goodness to be gained from having made them, you can cheerfully set them behind you and go on to the next big opportunity. But that is not enough: you should actively seek out opportunities just so you can then recover from them.

In science, you make your mistakes in public. You show them off so that everybody can learn from them. This way, you get the benefit of everybody else's experience, and not just your own idiosyncratic path through the space of mistakes. (Physicist Wolfgang Pauli famously expressed his contempt for the work of a colleague as "not even wrong". A clear falsehood shared with critics is better than vague mush.)

This, by the way, is another reason why we humans are so much smarter than every other species. It is not so much that our brains are bigger or more powerful, or even that we have the knack of reflecting on our own past errors, but that we share the benefits our individual brains have won by their individual histories of trial and error.

I am amazed at how many really smart people don't understand that you can make big mistakes in public and emerge none the worse for it. I know distinguished researchers who will go to preposterous lengths to avoid having to acknowledge that they were wrong about something. Actually, people love it when somebody admits to making a mistake. All kinds of people love pointing out mistakes.

Generous-spirited people appreciate your giving them the opportunity to help, and acknowledging it when they succeed in helping you; mean-spirited people enjoy showing you up. Let them! Either way we all win.

For nearly 20 years, Dr. James W. Pennebaker has been giving people an assignment: write down your deepest feelings about an emotional upheaval in your life for 15 or 20 minutes a day for four consecutive days. Many of those who followed his simple instructions have found their immune systems strengthened. Others have seen their grades improved. Sometimes entire lives have changed.

Pennebaker, a professor in the Department of Psychology at The University of Texas at Austin and author of several books, including Opening Up and Writing to Heal, is a pioneer in the study of using expressive writing as a route to healing. His research has shown that short-term focused writing can have a beneficial effect on everyone from those dealing with a terminal illness to victims of violent crime to college students facing first-year transitions.

"When people are given the opportunity to write about emotional upheavals, they often experience improved health," Pennebaker says. "They go to the doctor less. They have changes in immune function. If they are first-year college students, their grades tend to go up. People will tell us months afterward that it's been a very beneficial experience for them."

In his early research Pennebaker was interested in how people who have powerful secrets are more prone to a variety of health problems. If you could find a way for people to share those secrets, would their health problems improve?

Scientists have generated the first detailed pictures of the intricate events in the womb that result in the formation of the human brain. The study could prove to be a decisive breakthrough in understanding the many cognitive disorders thought to be triggered before birth - from autism to schizophrenia.

The researchers believe that the findings could one day lead to a "blueprint for building the human brain" based on knowing the precise sequence of genes that are selectively switched on and off in different parts of the embryonic organ during the critical stages of development in the womb.

Researchers at the Allen Institute for Brain Science in Seattle, funded by the Microsoft billionaire Paul Allen, analysed the brains of four human foetuses between 15 and 21 weeks to build up the first atlas of the developing brain based on differences in gene activities - a so-called "transcriptome".

The work is part of a much wider body of research aimed at a fundamental understanding of the brain, which is often described as the most complex structure in the known universe. Last month, President Obama announced the doubling of US Government funding on his brain initiative - from $100 million to $200 million.

Other approaches in the Obama initiative include the construction of intricate wiring diagrams of how the 100 billion nerve cells of the brain communicate with one another by sending electrical signals down physical connections, known as "connectomes".

Senior scientists believe that these revolutionary new techniques for studying the brain could transform our knowledge of how the brain works and so lead to radical new forms of prevention or treatment for the many psychological and developmental disorders that have so far defied medicine.

Brooklyn, N.Y. - Whether it's messy breakup or a traumatic car crash, there are some memories many of us would rather erase from our minds. Although the idea was explored in the 2004 film Eternal Sunshine of the Spotless Mind, the total erasure of conscious memories is no longer completely science fiction, says a neuroscientist who has been experimenting with such possibilities in rats.

New York University neuroscientist Joseph LeDoux's preliminary studies suggest the idea of erasing memories like a painful romantic breakup (as was the case in Eternal Sunshine) is possible in humans.

"What [the film characters] were doing, obviously, is impossible," LeDoux told an audience at a showing of the film here at the Brooklyn Academy of Music, as part of a program called Science on Screen. But "it's not so far-fetched as you might think," LeDoux said.

In Eternal Sunshine, the characters Joel (Jim Carrey) and Clementine (Kate Winslet) are a couple who have broken up, and Clementine decides to undergo a medical procedure to have her memories of Joel erased. When Joel finds out, he decides to undergo the same procedure, but it doesn't completely work, and he finds himself running around in his mind, trying to safeguard his memories of Clementine.

Night owls, people who stay up late at night, compared to early birds, people who wake up early in the morning, tend to be unmarried risk-takers.

Study author Dario Maestripieri, a professor in comparative human development at the University of Chicago, said women who are night owls share the same high propensity for risk-taking as men.

"Night owls, both males and females, are more likely to be single or in short-term romantic relationships versus long-term relationships, when compared to early birds," Maestripieri said in a statement. "In addition, male night owls reported twice as many sexual partners than male early birds."

The researchers used data from earlier research of more than 500 graduate students at the University of Chicago Booth School of Business, which assessed financial risk aversion among male and female students and found men more willing to take financial risks than women.

However, men with high levels of the male hormone were more similar to men in financial risk-taking.

• Just three years of poor sleep could cause a decline in mental faculties
• Poor sleep is linked to a 50% increase in risk of a decline in faculties
• Sleep quality is more important than quantity in determining brain ageing

Sleeping badly could age you as much as five years, a study has revealed. Just three or four years of broken sleep patterns are linked to a loss of memory and concentration, American researchers found.

They say that poor quality sleep is increases the risk of of having impaired mental faculties by up to 50 per cent - equivalent to a five year increase in age.

Study leader Dr Terri Blackwell, of the California Pacific Medical Centre Research Institute, in San Francisco, said: 'It was the quality of sleep that predicted future cognitive decline in this study, not the quantity.

'With the rate of cognitive impairment increasing and the high prevalence of sleep problems in the elderly, it is important to determine prospective associations with sleep and cognitive decline.'

The study, published in the journal Sleep, involved 2,820 men with an average age of 76 years.