The aging brain is more scattered and distractible. Is that unfiltered mind the foundation of intuitive wisdom? A fascinating new theory and study in the journal Psychological Science: We’re Only Human: Hyper-binding ain’t for sissies.

ADHD, or attention-deficit/hyperactivity disorder, is among the costliest of behavioral disorders. Its combination of inattention, impulsivity and hyperactivity leads to accidental injuries, school failure, substance abuse, antisocial behavior and more. Yet despite nearly a century of study, the disorder’s roots remain mysterious.

Much of modern ADHD research has focused on heritability of the condition, and indeed evidence suggests that genes may account for as much as 70 percent of hyperactivity and inattention in children. But that leaves 30 percent unexplained, so recently the focus has shifted to the environment. What is it that triggers an underlying susceptibility and changes it into a full-blown disorder? New research suggests that the culprit may be an old villain—lead—and what’s more it explains the causal pathway from exposure to disability.

Lead is a neurotoxin. This has been known for a long time, and in fact government regulation drastically reduced environmental lead a generation ago. But regulating automobile fuel and paint didn’t entirely eliminate lead from the environment. It’s found in trace amounts in everything from children’s costume jewelry to imported candies to soil and drinking water. Every American today is exposed to low levels of the metal, and indeed nearly all children have measureable levels of lead in their bodies. According to psychological scientist Joel Nigg of the Oregon Health & Science University, this universal low-level exposure makes lead an ideal candidate for the disorder’s trigger.

This was just a theory until quite recently, but two recent studies now provide strong evidence. The first study compared children formally diagnosed with ADHD to controls, and found that the children with the disorder had slightly higher levels of lead in their blood. This study showed a link only between blood lead and hyperactivity/impulsivity symptoms, not inattention. But a second study showed a robust link between blood lead and both parent and teacher ratings of ADHD symptoms, including both hyperactivity and attention problems. In both studies, the connection was independent of IQ, family income, race, or maternal smoking during pregnancy.

Nigg offers a causal model for the disabling symptoms associated with ADHD: Lead attaches to sites in the brain’s striatum and frontal cortex, where it acts on the genes in these regions—causing them to turn on or remain inactive. Gene activity shapes the development and activity of these brain regions. By disrupting brain activity, the toxin in turn alters psychological processes supported by these neurons, notably cognitive control. Finally, diminished cognitive control contributes to hyperactivity and lack of vigilance. Nigg describes his new data and his explanatory model in the February issue of the journal Current Directions in Psychological Science.

Many addiction recovery programs teach a principle called HALT. HALT is an acronym for Hungry-Angry-Lonely-Tired, and the idea is that any one of these conditions of mind and body can be a threat to continued sobriety. HALT is an article of faith, based on years of collective experience. It’s not considered all that important why these visceral states might be related to relapse.

But scientists think it’s important. Not the HALT principle itself, but the connection between bodily states and decisions, both good and bad. And new research may indeed shed some light on at least one part of the question: the link between food, hunger, and unsound judgment.

University of South Dakota psychological scientists X.T. Wang and Robert Dvorak wanted to see if blood sugar—the brain’s fuel—might affect the way we think about rewards, present and future. To do so, they recruited a group of volunteers, and measured their blood sugar in the lab. Then they gave them a series of choices like this one: “Would you prefer $120 tomorrow or $450 in 31 days?” The researchers varied the amounts of money and the time delays, but all the choices were between a small amount now and a large amount in the future. Or to put it in terms an addict would understand: Is a drink today worth more or less than a bigger reward over the long haul?

Then they all drank a can of Sprite. They weren’t taking a break; the soda was central to the experiment. What the volunteers didn’t know, however, was that half of them were drinking a regular Sprite, sweetened with sugar, while the others were drinking an artificially sweetened drink. Basically, the scientists were fueling the brains of only some volunteers, to see the effects on their subsequent decisions. After letting the sugar metabolize for ten minutes, they gave them a similar set of choices about present and future rewards.

The volunteers actually believed they might get the amount of money they chose. That was important, because it meant they were motivated to answer honestly. And their answers were revealing: As reported on-line this week in the journal Psychological Science, those who got the sugar jolt were much more likely to delay their rewards, taking more cash at some future time. Those who were depleted—physically and cognitively—were more apt to take the money and run.

What’s notable here is that the effect took place so rapidly—just ten minutes. That suggests that even moment-to-moment fluctuations in blood sugar can shape judgments, choices and decisions—and important ones. This raises the possibility, the scientists say, that carefully regulating blood sugar—and avoiding sharp fluctuations—might be a means of treatment for a range of impulsive disorders, including addictions. Some of course already know this as the H in HALT.

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Anyone who has ever experienced heartache knows that the “ache” is not metaphorical. Hearts and minds can hurt with the intensity of a migraine. Rejection and isolation can break one’s spirits as surely as a nasty fall can splinter a femur.

So why don’t we treat psychic pain the same way we treat our bodies’ agonies? This seemed like an obvious question to University of Kentucky psychologist Nathan DeWall, yet when he searched the scientific literature, he could find no attempts to even ask the question. So he did the obvious: He handed out Tylenol to see if the drug might soothe people’s emotional suffering.

DeWall and his colleagues ran two studies. In the first, they simply gave volunteers a 1000 milligram dose of acetaminophen—the active ingredient in Tylenol—while others took a placebo. The volunteers took the drug morning and night for three weeks, during which time they also filled out a daily measure of psychic pain. Those taking the painkiller showed a steady decline in social suffering over the three weeks, while the controls showed no such improvement.

That was an intriguing finding, so the scientists decided to actually watch the brain in action during a similar trial. In this experiment, the volunteers took 2000 milligrams of painkiller for three weeks. At the end of the three weeks, they (and others who had been taking a placebo) took part in computer game that had been rigged to make some players feel excluded, much as kids might feel rejected on the playground. They scanned their brains while they were playing the game, and the results were striking: In every volunteer who experienced rejection, the brain region associated with physical pain lit up—except in those who had been taking Tylenol. In other words, the brain experienced pain just as real as it would if the body had been wounded, and the drug effectively salved that pain. The results will appear in the journal Psychological Science this spring.

The psychologists are not advocating that the forlorn and lonely masses run to the pharmacy to stock up on Tylenol. The drug is not great on the liver, especially in such large and frequent doses. But the findings do point toward a new line of inquiry on the link between physical and emotional pain, and may lead someday to interventions for severe social pain. The pain of chronic loneliness, the researchers say, is as harmful to health as obesity and tobacco.

When South Carolina Governor Mark Sanford was caught red-handed returning from a tryst with his Argentine mistress last June, he told the Associated Press that he had met his “soul mate.” His choice of words seemed to suggest that having a deep emotional and spiritual connection with Maria Belen Chapur somehow made his sexual infidelity to his wife Jenny Sanford less tawdry.

Jenny Sanford wasn’t buying it, and neither would most women. What the two-timing governor didn’t understand is that most women view emotional infidelity as worse, not better, than sexual betrayal. Publicly acknowledging a soul connection was probably the most insulting and hurtful thing he could have said to his wife of 20 years.

The clueless governor is not alone. Research has documented that most men become much more jealous about sexual infidelity than they do about emotional infidelity. Women are the opposite, and this is true all over the world. Just why this is the case is not fully understood, although the prevailing theory is that the difference has evolutionary origins: Men learned over eons to be hyper-vigilant about sex because they can never be absolutely certain they are the father of a child, while women are much more concerned about having a partner who is committed to raising a family.

New research now suggests an alternative explanation. The new studies do not question the fundamental gender difference regarding jealousy—indeed they add additional support for that difference. But the new science suggests that the difference may be rooted more in personality—specifically in traits like self-reliance and insecurity.

Pennsylvania State University scientists Kenneth Levy and Kristen Kelly doubted the evolutionary explanation because there is a conspicuous subset of men who are more like women. That is, they find emotional betrayal more distressing than sexual infidelity. Why would this be? The researchers suspected that it might have to do with trust and emotional attachment. Some people—men and women alike—are by nature more secure in their attachments to others, while others are more invested in their own autonomy and seemingly less in need of intimacy.  Psychologists see this compulsive self-reliance as a defensive strategy—protection against deep-seated feelings of vulnerability. People high on this trait tend to be preoccupied with the sexual aspects of relationships rather than emotional intimacy.

Levy and Kelly decided to explore a possible link between attachment style and jealousy style, and they did this by running a group of volunteers through some standard psychological tests. One questionnaire measured whether the volunteers were secure in their romantic relationships, or whether they instead were avoidant and noncommittal. A second questionnaire asked which they would find more distressing—knowing their partner was off having passionate sexual intercourse with someone else, or knowing that same partner had formed a deep emotional attachment with someone else.

They sorted the data, and the conclusions were indisputable. As the scientists reported on-line in the journal Psychological Science this week, avoidant types—those who prize their autonomy in relationships over commitment—were much more upset about sexual infidelity than emotional infidelity. And conversely, emotionally secure volunteers—including secure men—were much more likely to find emotional betrayal more upsetting.

But here’s the interesting twist. Just like all the earlier studies, Levy and Kelly found clear evidence of a gender difference in jealousy style. In other words, men are indeed preoccupied with sexual betrayal, and women the reverse, but not for the reasons we thought. Men fret about sexual betrayal because they are overly invested in the sexual side of their own relationship—and that superficiality is linked to their thin romantic attachments. Not to put too fine a point on it, male jealousy is shaped by deep emotional insecurities. Jenny Sanford probably knew that already, and the governor’s soul mate is no doubt having her suspicions by now.