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"MIT researchers have shown, for the first time ever, that memories are stored in specific brain cells. By triggering a small cluster of neurons, the researchers were able to force the subject to recall a specific memory. By removing these neurons, the subject would lose that memory. As you can imagine, the trick here is activating individual neurons, which are incredibly small and not really the kind of thing you can attach electrodes to. To do this, the researchers used optogenetics, a bleeding edge sphere of science that involves the genetic manipulation of cells so that they're sensitive to light. These modified cells are then triggered using lasers; you drill a hole through the subject's skull and point the laser at a small cluster of neurons. Now, just to temper your excitement, we should note that MIT's subjects in this case are mice - but it's very, very likely that the human brain functions in the same way. To perform this experiment, though, MIT had to breed genetically engineered mice with optogenetic neurons - and we're a long, long way off breeding humans with optogenetic brains. In the experiment, MIT gave mice an electric shock to create a fear memory in the hippocampus region of the brain (pictured above) - and then later, using laser light, activated the neurons where the memory was stored. The mice "quickly entered a defensive, immobile crouch," strongly suggesting the fear memory was being recalled."

"Jerome Kagan's "Aha!" moment came with Baby 19. It was 1989, and Kagan, a professor of psychology at Harvard, had just begun a major longitudinal study of temperament and its effects. Temperament is a complex, multilayered thing, and for the sake of clarity, Kagan was tracking it along a single dimension: whether babies were easily upset when exposed to new things. He chose this characteristic both because it could be measured and because it seemed to explain much of normal human variation. He suspected, extrapolating from a study he had just completed on toddlers, that the most edgy infants were more likely to grow up to be inhibited, shy and anxious. Eager to take a peek at the early results, he grabbed the videotapes of the first babies in the study, looking for the irritable behavior he would later call high-reactive. Enlarge This Image Mickey Duzyj Related Letters: The Anxious Mind (October 18, 2009) Health Guide: Anxiety Enlarge This Image Mickey Duzyj Enlarge This Image Mickey Duzyj Enlarge This Image Mickey Duzyj Enlarge This Image Mickey Duzyj Readers' Comments Readers shared their thoughts on this article. Read All Comments (191) » No high-reactors among the first 18. They gazed calmly at things that were unfamiliar. But the 19th baby was different. She was distressed by novelty - new sounds, new voices, new toys, new smells - and showed it by flailing her legs, arching her back and crying. Here was what Kagan was looking for but was not sure he would find: a baby who essentially fell apart when exposed to anything new. Baby 19 grew up true to her temperament. This past summer, Kagan showed me a video of her from 2004, when she was 15. We sat in a screening room in Harvard's William James Hall - a building named, coincidentally, for the 19th-century psychologist who described his own struggles with anxiety as "a horrible dread at the pit of my stomach ... a sense of the insecurity of life." Kagan is elfin and spry, ba

"Is free will an illusion? Some leading scientists think so. For instance, in 2002 the psychologist Daniel Wegner wrote, "It seems we are agents. It seems we cause what we do… It is sobering and ultimately accurate to call all this an illusion." More recently, the neuroscientist Patrick Haggard declared, "We certainly don't have free will. Not in the sense we think." And in June, the neuroscientist Sam Harris claimed, "You seem to be an agent acting of your own free will. The problem, however, is that this point of view cannot be reconciled with what we know about the human brain." Many neuroscientists are employing a flawed notion of free will. Such proclamations make the news; after all, if free will is dead, then moral and legal responsibility may be close behind. As the legal analyst Jeffrey Rosen wrote in The New York Times Magazine, "Since all behavior is caused by our brains, wouldn't this mean all behavior could potentially be excused? … The death of free will, or its exposure as a convenient illusion, some worry, could wreak havoc on our sense of moral and legal responsibility." Indeed, free will matters in part because it is a precondition for deserving blame for bad acts and deserving credit for achievements. It also turns out that simply exposing people to scientific claims that free will is an illusion can lead them to misbehave, for instance, cheating more or helping others less. [1] So, it matters whether these scientists are justified in concluding that free will is an illusion. "