When I was a 14-year-old in a suburb of Dublin, we were at the height of “the Troubles.” During this period of civil unrest, our school regularly took in girls from Northern Ireland to get them away from the bomb blasts and shootings in Belfast, some two hours' drive across the border. One of these girls was named Sandra, and she had been at our school for a couple of weeks when one day the two of us decided to walk home for lunch. As I was walking and chatting, I suddenly became aware that Sandra was no longer beside me.

Looking around, I saw her about 10 meters back, lying flat on the pavement. A car had backfired, and she had instantly thrown herself on the ground. Deep in her brain, an alarm signal had gone off. That same signal had slipped past me unnoticed.

How we interpret the events in our lives determines their significance to us. Often these incidents are ambiguous: they may represent a threat, as in gunfire, or they may be neutral, as in a car backfiring. Our responses reveal something deeper about the way our brain analyzes what is happening around us. To a mind sculpted by a violent and dangerous environment, a loud bang is highly salient.

Ambiguous situations crop up all the time, particularly in the social world. Perhaps your boss rushes past you one morning at the office. Her brusque demeanor could signal that she is annoyed with you, or it could mean she is running late to a meeting. New research tells us that subtle, subliminal biases in interpreting such events can affect our life trajectory. Through some combination of genetics and personal experiences, we can develop a habit of seeing the proverbial glass as either half full or half empty. That frame of mind in turn alters our resilience to adversity, for better or worse.

Cognitive psychologists have long known that people who rate higher on measures of anxiety and depression—my colleagues and I call it emotional vulnerability—tend to draw overly negative conclusions when faced with ambiguous social situations. We also know that people who react more emotionally to adversity are at a higher risk of acquiring disorders of anxiety and depression the next time they encounter a stressful period.

A growing body of evidence now suggests that cognitive biases are the reason that some of these emotional disorders arise and stay entrenched. A tendency to notice, analyze and mull over threatening events can lead us to believe in a more menacing world than when we routinely see the sunny side of life. An emerging field known as cognitive-bias modification (CBM) aims to turn these negative predilections around, to instill more positive assessments and to bolster our defenses against stress.

Toxic Tendencies

Hundreds of psychology experiments support the view that we possess ingrained biases that correlate with a person's ability to weather life's ups and downs. Biases direct our thinking at several levels, including what we pay attention to, how we interpret our experiences and what we end up storing in memory. Psychologists have developed ingenious tools for measuring these mental habits under highly controlled laboratory conditions.

One simple way to assess how we interpret things is to ask people to listen to someone saying numerous homophones, which are words that sound alike but have different spellings, and to write down the word they hear. For example, homophones such as dye and die or pane and pain sound the same but have either a negative or a benign meaning. A program of research started by psychologist Michael Eysenck, now emeritus at the University of London, and his colleagues in the 1980s has shown us that those who rate higher on measures of anxiety are more likely to write down the negative spellings, whereas those who are low in anxiety give equal weight to both negative and benign words.

Other tests can investigate biases in what we pay attention to. One approach is to use software that flashes images of different scenes. Study participants may see, for example, a pair of facial expressions on a computer screen before a single letter replaces them on the display. Half the time the letter appears where a hostile face had been, and half the time it pops up in the space previously occupied by a smiling visage. Participants are asked to push the appropriate button when they see a letter and to ignore the images. Over hundreds of trials researchers have observed that people who are emotionally vulnerable respond faster when the target appears near a hostile face, whereas resilient people react more quickly when the target lands near a joyful face. This simple gamelike activity, called the attentional probe task, reveals our habit of tuning into the negative or the positive at lightning-fast speed.

In everyday life a pessimistic pattern can work against us. A socially anxious person giving a speech, for instance, might focus on the bored or mildly hostile face in the crowd without noticing the many engaged listeners in the audience. Over time a negative bias in attention can help construct a more hostile view of the world than if a person's focus lands instead on friendly, accepting faces. A simple modification to the attentional probe task, however, can allow us to unseat subliminal biases—for therapeutic effect.

A Better Bias?

Psychologist Colin MacLeod of the University of Western Australia was one of the first to try to deliberately shift subliminal habits. In 2002 his team found that it could train students to either notice or tune out threatening words such as cancer or rape. The students saw a nasty word and a neutral term displayed simultaneously on a computer screen. A split second later a target letter appeared on the screen to which people had to respond as quickly as they could by pressing a button.

Half the students saw the letter always appear where the nasty word had been. For the others, the letter inevitably replaced the neutral word. After hundreds of these events, participants who were trained to avoid the threatening words responded much faster when the target letter was juxtaposed with the neutral word, and the subjects who had focused on the nasty words were correspondingly much swifter when responding to letters that supplanted the negative word.

The students were then subjected to a mildly stressful test. They were given a limited amount of time to solve a series of difficult anagrams, some of which were impossible. The participants who had been trained to notice threat reported more stress than those who had been trained to steer clear of the unpleasant words. This finding, though limited to subjective report, was the first glimmer that practicing attending to negative versus neutral features can determine how we react in real-life situations.

In subsequent studies, the same team tested young students from Singapore weeks before they were due to travel to Australia to attend university there. Half of the participants underwent the same threat-avoidance training, with letters appearing where neutral words had been. The remaining students were given a placebo training regimen, the goal of which was to instill no bias at all. These participants viewed the same sets of words, but the target letter appeared equally often in the locations of the threatening and benign words.

For three weeks students underwent several sessions of their assigned training condition before catching a flight to Australia. MacLeod's team met the students at Perth's airport and measured how well they adjusted during their first few weeks in the new country. The results showed that those who had practiced avoiding threat before they left home were less stressed and less anxious when they arrived in their new environment as compared with those who had received placebo training.

As with attention, our interpretational style can also be modified. Andrew Mathews and Bundy Mackintosh of the MRC Cognition and Brain Sciences Unit in Cambridge, England, presented people with a series of ambiguous scenarios such as the following:

“You have decided to go caving even though you feel nervous about being in an enclosed space. Going deep inside the cave, you realize you have completely lost your __”

This description is followed by a word fragment such as w_ y (“way” is a negative outcome), or f_ar (“fear” is a positive outcome). Participants filled in the fragments in about 100 different ambiguous scenarios for about an hour. One day later the subjects watched video clips of accidents. Those who had formulated positive resolutions reported less anxiety and demonstrated less stress when compared with those who had repeatedly rehearsed negative resolutions. Other work has confirmed that inducing a more benign style of interpreting potentially scary situations can have direct effects on how well people cope with subsequent stress and adversity. These initial studies laid the groundwork for a slew of recent investigations into CBM in clinical populations.

A Vaccine against Negativity

Most cognitive theories of emotional disorders assume that subconscious biases increase the frequency and intensity of conscious negative thoughts. One influential theory of social anxiety disorder outlined by University of Oxford psychologist David M. Clark, for example, posits that preferentially noticing ominous external social signals, such as frowning faces, and negative internal cues, such as the sensation of blushing, can produce anxious feelings and a bleak self-evaluation—two key features of the disorder. Both anxiety and depression are associated with persistent tendencies to focus on either threatening or unflattering information, to interpret environmental cues pessimistically and to recall more unhappy memories. As a result, an obvious next step is to consider whether CBM could improve these symptoms in clinical populations.

Beginning around 2008, several experiments have done just that. A 2011 meta-analysis—a study of studies—reviewed 12 randomized controlled trials involving people diagnosed with a variety of anxiety disorders. The studies all consisted of about 16 sessions across a number of weeks and used the attentional training method developed by MacLeod and his colleagues. The authors concluded that training in avoiding threats was more effective than the placebo activity in alleviating the symptoms of clinical anxiety disorder in adult patients. A more recent study investigated CBM's effect on childhood anxiety disorders. In 2012 psychologist Yair Bar-Haim of Tel Aviv University reported that ratings of anxiety symptoms by the children, parents and clinicians declined as compared with placebo training after four weekly sessions.

Other researchers have explored attentional training in depression, in particular whether it can serve as a “cognitive vaccine” against relapse. Although both drug and talk therapies can ease depression temporarily, all are highly ineffective a year or more later. Around 60 percent of those who suffer from major depressive disorder relapse within a year regardless of whether they are taking antidepressants or engaged in talk therapy.

Among the strongest predictors of relapse are negative cognitive biases. To investigate whether we can unseat these mental habits, psychiatrist Michael Browning of Oxford and his colleagues selected 61 patients who had experienced at least two serious episodes of major depression but were in remission. Half were placed in a CBM training program designed to orient their attention toward positive rather than neutral faces or words. The others practiced a placebo training activity. The researchers evaluated their subjects' progress using a standard depression questionnaire and samples of their salivary cortisol. Negative responses to the questionnaire items and high amounts of this stress response hormone are also predictors of relapse.

The results were mixed, but in a telling way: CBM training with words was no better than placebo, but CBM using faces was highly effective in reducing depression symptoms when compared with placebo training. Learning to orient toward happy, smiling faces reduced the number of downbeat responses on the questionnaire. It also lowered the levels of salivary cortisol. Because this therapeutic approach is still young, further studies will need to iron out such details as whether faces versus words are more effective in various contexts.

Plan of Action

We also lack a solid understanding of why CBM might work. Most treatments used to tackle emotional problems, including cognitive-behavior therapy (CBT), mindfulness-based meditation and antidepressants, involve several components. The premise behind CBT, a widely used treatment for disordered thinking, is that learning to adjust or cope with maladaptive thought patterns can lead to emotional and behavioral change. A strong relationship with a therapist is usually important, and recipients of the therapy often complete exercises that challenge overly negative beliefs. CBM techniques might thus be a distillation of one essential aspect of more complex therapeutic interventions. If CBM matures into a fully accepted therapy, it will almost certainly become incorporated into a more complex regimen, such as CBT, rather than deployed on its own.

Indeed, a procedure intended to help people with drinking problems has already produced promising initial results when used with CBT. This version of CBM, unlike the others described here, involves an active component. In an experiment led by psychologist Reinout Wiers of the University of Amsterdam, 214 patients struggling with alcoholism used a joystick to either push or pull images of beverages on a screen. For example, participants might push away a picture of a bottle of beer, causing it to shrink in size, and pull closer a picture of a soft drink, making it grow larger on the screen. A year later individuals who had pushed back the alcoholic drinks and drawn forward the benign beverages were significantly less likely to have relapsed than subjects who had pushed and pulled equal numbers of both types of drinks.

The strong outcome suggests that incorporating a meaningful action—such as rejecting bad items and embracing positive ones—into CBM training could strengthen this therapy. Yet these are early days. Future research will need to test not only what training stimuli work best but also how enduring the changes are. Should therapies involve recurring top-ups of CBM, and if so, how often?

One particularly appealing angle of this new therapeutic approach is the ease with which it can be delivered on computers, smartphones or tablets. A person could visit his therapist, for instance, and leave with a tailor-made CBM intervention on his mobile device to help him through the tough times ahead. Healthy people, too, might use these techniques to boost a more resilient frame of mind so that they can flourish, rather than simply getting by.

Even simple techniques can shake loose a negative mood. Keeping a diary of the day's events, for example, can remind you later of the good things that may have been forgotten. Changing routines can also interrupt a dark period. Take a different route to the grocery store, for example, or call up a friend out of the blue. Lastly, giving yourself a 15-minute break from your day can help calm a stressed-out brain. A quick jaunt outside with a switched-off mobile phone can give a turbulent mind a chance to settle down. Whether coping with a bad day or a lingering malaise, cultivating healthy mental habits can bring optimism back for good.