Researchers at the University of Kentucky were interested in the link between low glucose levels and aggressive behavior… […]

When you go several hours without eating, your blood sugar drops. Once it falls below a certain point, glucose-sensing neurons in your ventromedial hypothalamus, a brain region involved in feeding, are notified and activated resulting in level fluctuations of several different hormones. Ghrelin, a hormone that increases expression when blood sugar gets low and stimulates appetite through actions of the hypothalamus, has been shown to block the release of the neurotransmitter serotonin. The serotonin system is incredibly complex and contributes to a number of different central nervous system functions. One of the many hats this neurotransmitter wears is modulation of emotional state, including aggression. […]

If you have a predisposition to aggression, low serotonin levels circulating in your brain may lead to altered communications between brain regions that wrangle aggressive behavior.

{ Synaptic Scoop | Continue reading }

Many scholars have argued that Nietzsche’s dementia was caused by syphilis. A careful review of the evidence suggests that this consensus is probably incorrect. The syphilis hypothesis is not compatible with most of the evidence available. Other hypotheses – such as slowly growing right-sided retro-orbital meningioma – provide a more plausible fit to the evidence.

{ Journal of Medical Biography | PDF }

From his late 20s onward, Nietzsche experienced severe, generally right- sided headaches. He concurrently suffered a progressive loss of vision in his right eye and developed cranial nerve findings that were documented on neurological examinations in addition to a disconjugate gaze evident in photographs. His neurological findings are consistent with a right-sided frontotemporal mass. In 1889, Nietzsche also developed a new-onset mania which was followed by a dense abulia, also consistent with a large frontal tumor. […] An intracranial mass may have been the etiology of his headaches and neurological findings and the cause of his ultimate mental collapse in 1889.

{ Neurosurgery | PDF }

The more you multitask, the worse you get at it.

{ Priceonomics | Continue reading | More: Media multitaskers performed worse on a test of task-switching ability | PDF }

At this very moment, your eyes and brain are performing an astounding series of coordinated operations.

Light rays from the screen are hitting your retina, the sheet of light-sensitive cells that lines the back wall of each of your eyes. Those cells, in turn, are converting light into electrical pulses that can be decoded by your brain.

The electrical messages travel down the optic nerve to your thalamus, a relay center for sensory information in the middle of the brain, and from the thalamus to the visual cortex at the back of your head. In the visual cortex, the message jumps from one layer of tissue to the next, allowing you to determine the shape and color and movement of the thing in your visual field. From there the neural signal heads to other brain areas, such as the frontal cortex, for yet more complex levels of association and interpretation. All of this means that in a matter of milliseconds, you know whether this particular combination of light rays is a moving object, say, or a familiar face, or a readable word. […]

This post is about a question that’s long been debated among scientists and philosophers: At what point in that chain of operations does the visual system begin to integrate information from other systems, like touches, tastes, smells, and sounds? What about even more complex inputs, like memories, categories, and words?

We know the integration happens at some point. If you see a lion running toward you, you will respond to that sight differently depending on if you are roaming alone in the Serengeti or visiting the zoo. Even if the two sights are exactly the same, and presenting the same optical input to your retinas, your brain will use your memories and knowledge to put your vision into context

{ Virginia Hughes/National Geographic | Continue reading }

photo { Harry Callahan }

A surge of electrical activity in the brain could be responsible for the vivid experiences described by near-death survivors, scientists report.

A study carried out on dying rats found high levels of brainwaves at the point of the animals’ demise.

US researchers said that in humans this could give rise to a heightened state of consciousness.

{ BBC | Continue reading }

In two experiments we showed that exposure to an incidental black and white visual contrast leads people to think in a “black and white” manner, as indicated by more extreme moral judgments.

Participants who were primed with a black and white checkered background while considering a moral dilemma (Experiment 1) or a series of social issues (Experiment 2) gave ratings that were significantly further from the response scale’s mid-point, relative to participants in control conditions without such priming.

These findings suggest that in addition to affective cues and gut feelings, non-affective cues relating to processing style can influence moral judgments.

{ ScienceDirect }

art { Lorna Simpson }

In human psychology, overconfidence is typically taken to be the overestimation of one’s own capabilities. This, and other apparent cognitive biases such as optimism, are well-documented phenomena whose underlying neural mechanisms are becoming known. However, a convincing evolutionary explanation of such phenomena is lacking.

Two recent high-profile publications have advanced proposals for evolutionary explanations of overconfidence. […] The first proposal, a model by Johnson and Fowler (J&F), […] considers a scenario in which individuals compare their estimated fighting ability against that of potential opponents when deciding whether to contest a resource, doing so only if they perceive themselves as more capable. By identifying conditions under which individuals should overestimate their fighting ability, J&F claim to show that overconfidence should evolve.

The second is Trivers’ theory of self-deception. […] Among Trivers’ primary arguments for the evolution of cognitive bias are that selective pressure exists for animals to deceive each other and that deception is more effective, and less cognitively costly, when the deceiver believes the deception; in the context of animal conflict, the explanation of overconfidence would be that acting as if one’s abilities are greater than they really are can more effectively dissuade others from competition.

[…]

We argue that recent proposals, focused on benefits from overestimating the probability of success in conflicts or practicing self-deception to better deceive others, are still lacking in crucial regards. Attention must be paid to the difference between cognitive and outcome biases; outcome biases are suboptimal, yet cognitive biases can be optimal.

[…]

Cognitive bias: an inaccurate view of the world. This is a psychological definition. A cognitive bias might produce rational behavior or might result in an outcome bias.

Outcome bias: a departure from rational behavior. This is an operational definition.

{ Cell | PDF }

Sex pheromones are chemical compounds released by an animal that attract animals of the same species but opposite sex. They are often so specific that other species can’t smell them at all, which makes them useful as a secret communication line for just that species. But this specificity raises an intriguing question: When a new species evolves and uses a new pheromone signaling system, what comes first: the ability to make the pheromone or the ability to perceive it? […]

Any individuals that make a new and different scent would then be perceived by the receivers as being the wrong species and they won’t attract any mates. If you don’t attract mates, you can’t pass on your new genes for your new scent. This produces a strong pressure to make a scent that is as similar as the scent produced by everyone else as possible (this is called stabilizing selection). With this intense pressure to be like everyone else, how did the incredible diversity of species-specific pheromones come to be?

{ Nature | Continue reading }

The prevailing view in psychology is that materialism is bad for our well-being. Research by Tim Kasser (at Knox College) and others has revealed an association between holding materialist values and being more depressed and selfish, and having poorer relationships. Kasser has previously called for a revolution in Western culture, shifting us from a thing-centred to a person-centred society. Other research by Leaf Van Boven, Thomas Gilovich and colleagues has shown that the purchase of experiences leaves people happier than buying material products. In another study of theirs, materialistic people were liked less than people who appeared more interested in experiences.

{ The Psychologist | PDF }

images { 1 | 2 }

Analyzing data from 60 earlier studies, Solomon Hsiang from the University of California, Berkeley, found that warmer temperatures and extremes in rainfall can substantially increase the risk of many types of conflict. For every standard deviation of change, levels of interpersonal violence, such as domestic violence or rape, rise by some 4 percent, while the frequency of intergroup conflict, from riots to civil wars, rise by 14 percent. Global temperatures are expected to rise by at least two standard deviations by 2050, with even bigger increases in the tropics.

{ The Scientist | Continue reading }

Since the size, density, and even shape of a person’s skull is somewhat unique, that resonance will vary across individuals. Our current research was designed to explore whether this uniqueness in skull resonance might have a direct influence on the kinds of music a person prefers. […] this research suggests that the skull [shape and size] might influence the music that a person dislikes rather than the music a person likes.

{ Acoustical Society of America/Improbable | Continue reading }

In the middle of the 20th century, experimental psychologists began to notice a strange interaction between human vision and time. If they showed people flashes of light close together in time, subjects experienced the flashes as if they all occurred simultaneously. When they asked people to detect faint images, the speed of their subjects’ responses waxed and waned according to a mysterious but predictable rhythm. Taken together, the results pointed to one conclusion: that human vision operates within a particular time window – about 100 milliseconds, or one-tenth of a second.

[…] Pretty much anyone with a pair of eyes will tell you that vision feels smooth and unbroken. But is it truly as continuous as it feels, or might it occur in discrete chunks of time?

{ Garden of the Mind | Continue reading }

screenshot { Ivan Mozzhukhin, Le brasier ardent, 1923 }

“Never give up” has become one of the most popular pieces of advice in Western culture.[…] Many worthwhile goals require serious commitment and perseverance in order to achieve them. The problem with this advice is that at some point in our lives, we all have goals that are unattainable, and this is where “never give up” falls short. […]

Results showed that the tendency to disengage from unattainable goals was associated with lower life stress, fewer intrusive thoughts about one’s problems, and feeling more control over one’s life. The flip side of this is that the tendency to stay engaged with unattainable goals was associated with more stress, more intrusive thoughts, and feeling less control. 

{ Psych Your Mind | Continue reading }

The pressures and expectations of the market weigh heavily on everyone. The erosion of long-term stability in employment means that people are expected to throw themselves into any job they find. Every minor task or training exercise must be met with absolute enthusiasm, as if motivation were something that could be turned on or off at will.

Such behaviour is impossible to sustain, and exacts its toll: depressive feelings, physical and emotional exhaustion at the expenditure of energy on projects we care little about.

Motivation loses its roots in our childhood interests and ideals, and becomes something external to us. Hence the oscillation between hyper-motivation and depletion characteristic of the contemporary worker.

{ The Guardian | Continue reading }

art { Kevin Barton }

On a street in Manhattan’s Lower East Side, an unremarkable gray box protrudes from a telephone pole. Inside the box lies a state-of-the-art airflow-sampling device, one part of an experiment to track how a gas disperses through the city’s streets and subway system. […]

The goal of the project is to develop a model for how a dangerous airborne contaminant, such as sarin gas or anthrax, would spread throughout the city in the event of a terrorist attack or accidental release.

The scientists released tiny amounts of a colorless, nontoxic gas at several locations around the city. The airflow samplers, located at various points throughout the city, measured the gas to determine how fast and how far it spread.

{ LiveScience | Continue reading }

unrelated { Eproctophilia is a paraphilia in which people are sexually aroused by flatulence. The following account presents a brief case study of an eproctophile. | Improbable }

First, about how glaciers turn into ocean water.

Consider this experiment. Take a large open-top drum of water and poke a hole near the bottom. Measure the rate at which water comes out of the hole. As the amount of water in the drum goes down, the rate of flow out of the hole will normally decrease because the amount of water pressure behind the hole decreases. Now, have a look at a traditional hourglass, where sand runs from an upper chamber which slowly empties into a lower chamber which slowly fills. If you measure the rate of sand flow through the connecting hole, does it decrease in flow rate because there is, over time, less sand in the upper chamber? I’ll save you the trouble of carrying out the experiment. No, it does not. This is because the movement of sand from the upper to lower parts of an hourglass is an entirely different kind of phenomenon than the flow of water out of the drum. The former is a matter of granular material dynamics, the latter of fluid dynamics.

Jeremy Bassis and Suzanne Jacobs have recently published a study that looks at glacial ice as a granular material, modeling the ice as clumped together ice boulders that interact with each other either by sticking together or, over time, coming apart at fracture lines. This is important because, according to Bassis, about half of the water that continental glaciers provide to the ocean comes in the form of ice melting (with the water running off) but the other half consists of large chunks (icebergs) that come off in a manner that has been very hard to model.

{ Greg Laden/ScienceBlogs | Continue reading }

For a couple years now I’ve been fascinated by some recent ideas about how complexity evolves. Darwin’s great insight was recognizing how natural selection could create complex traits. All that was needed was a series of intermediates that raised the reproductive success of organisms. But recently some researchers have developed ideas in which natural selection doesn’t play such a central role.

One idea, laid out in the book Biology’s First Law, holds that life has a built-in propensity to get more complex–even in the absence of natural selection. According to another idea, called constructive neutral evolution, mutations can change simple structures into more complex ones even if those mutations don’t provide an advantage. The scientists who are championing these ideas don’t see them as refuting natural selection, but, rather, complementing it, and enriching our understanding of how evolution works.

{ Carl Zimmer | Continue reading | More: Scientists are exploring how organisms can evolve elaborate structures without Darwinian selection }

{ Men who score high on psychopathy are better at lie detection; opposite pattern for women. | via BPS }

art { James Turrell }

The sense of smell is one of our most powerful connections to the physical world. Our noses contain hundreds of different scent receptors that allow us to distinguish between odours. When you smell a rose or a pot of beef stew, the brain is responding to scent molecules that have wafted into your nose and locked on to these receptors. Only certain molecules fit specific receptors, and when they slot together, like a key in a lock, this triggers changes in cells. In the case of scent receptors, specialised neurons send messages to the brain so we know what we have sniffed. […]

In the last ten years, however, reports have trickled in from bemused biologists that these receptors, as well as similar ones usually found on taste buds, crop up all over our bodies.

{ BBC | Continue reading }

Sound waves with frequencies just above human hearing can levitate tiny particles and liquid droplets and even move them around, a team of engineers has demonstrated. […]

In the new research, the team […] uses the setup to lift and spin a toothpick. Previously, no one had been able to control objects larger than a few millimeters in diameter.

{ Science | Continue reading }