Last October (2008), a large email provider launched a new application, the so-called mail goggles, that requires people to quickly solve five moderately complex math problems before they are allowed to send out any email. By default, these mail goggles are only active late night on the weekend (which led some people to rename this application ‘Beer Goggles’), but it can be adjusted to any self-chosen time window. The application is meant to withhold people from sending emails they would later regret.

Why should arithmetic be effective in preventing people from sending emotional emails? As one of the application’s engineers argues, people are especially likely to become emotional when intoxicated. Because solving math problems is not an easy task when one isn’t entirely sober, the equations thus form an extra barrier against impulsive drunkards venting their frustrations. But the effectiveness of mail goggles may be as much about the effort of doing math as it is about getting the answer right. That is, recent experimental findings have demonstrated that performing a cognitive task can take the edge of negative emotional responses and help people put things into a more neutral perspective ( Morrow & Nolen-Hoeksema, 1990; Van Dillen & Koole, 2007). Thus, even when people successfully pass the math obstacle, they may still be less inclined to send out any emotional email because doing the math has eased their minds. The idea is straightforward: stuff your head with numbers, instead of irrational ideas about getting back together with your ex.

But how exactly can numbers replace feelings? Research suggests it is because both cognitive tasks and emotional responses make use of the same limited mental resources (Baddeley, 2007; Siemer, 2005; Van Dillen & Koole, 2007). Granted that this limitation has certain drawbacks (most people can’t call, drive, and eat simultaneously), it may have some benefits as well. That is, the resources that are used to perform a cognitive task are no longer available for emotional processes. Accordingly, people can rid themselves from unwanted feelings by engaging in a cognitive activity, such as doing math equations (Van Dillen & Koole, 2007), playing a game of Tetris ( Holmes, James, Coode-Bate, & Deeprose , 2008), visualizing scenes such as sitting in a double-decker bus driving down the street (Rusting & Nolen-Hoeksema, 1998), sorting cards ( Morrow & Nolen-Hoeksema, 1990), responding to colored lights ( Christenfeld, 1997), or filling out bogus questionnaires ( Glynn et al., 2002).

Not All Distractions Are Created Equal

Whereas a diverse range of cognitive tasks can distract people from their negative feelings, not just any task is equally effective. For example, a simple motor task (such as walking back and forth) less successfully distracts people from a depressive mind state than a more cognitive task (sorting countries from most to least industrialized; Morrow & Nolen-Hoeksema, 1990). Likewise, simply showing people positive pictures does not alleviate people’s negative moods, whereas combining these pictures with a short riddle does ( Strick, Holland, Van Baaren & Van Knippenberg, under review). Because simple or over learned activities like walking and passive viewing can be performed relatively automatically, they do not rely on people’s limited mental resources (Bargh, 1994; Saling & Phillips, 2007). As a consequence, performing these activities hardly competes with emotional processing.

In other words, activities should distract people from their negative feelings to the degree that these activities incorporate mental resources: the more mental resources are needed to perform a task, the more emotional responses will be attenuated. In support of this, people report a greater reduction in negative mood when they perform a highly demanding task (i.e. solving complex, or unpredictable math problems) than when they perform a mildly demanding task (e.g. solving simple, or predictable math problems), whereas performing a mildly demanding task is still more distracting than performing no task at all (Erber & Tesser, 1992; (Van Dillen & Koole, 2007).

The Limited Resources of the Emotional Brain

If emotional information competes with non-emotional information for limited mental resources, this may be reflected in the dynamics of the brain systems involved. Several neuro-imaging studies have investigated how performing complex cognitive tasks can modulate emotional responses in the brain (Erk, Kleczar & Walter, 2007; Pessoa, Ungerleider, Gutierrez, McKenna, 2002; Van Dillen, Heslenfeld & Koole, 2009). For example, one study found that solving complex math equations attenuates responses to negative scenes in brain regions that are part of the emotion network, whereas performing the math task results in increased activity in regions that are part of the cognitive network in the brain (Van Dillen, Heslenfeld & Koole, 2009). Interestingly, there seems to be a linear relationship between these opposed neural patterns, such that the more cognitive brain regions are engaged during the task, the more activity in emotional brain regions are attenuated (Erk et al., 2007; Van Dillen, Heslenfeld & Koole, 2009).

Other researchers have reported similar effects of task complexity on brain responses to painful stimuli (Bantick et al., 2002;Frankenstein, Richter, McIntyre, & Remy, 2001; Tracey et al., 2002; Valet, et al., 2004). In one experiment, participants performed a counting task during which they received painful thermal stimulation. The counting task consisted of naming the number of words on screen regardless of the words’ meaning. Task complexity was manipulated by varying the possible interference of the words with the counting task (Bush et al., 1998), such that in the difficult task condition, participants had to count interfering number words, e.g. ‘eight’ or ‘five’, while in the easy task condition participants had to count neutral words, e.g. ‘cat’ or ‘frog’. Compared to the easy counting task, performing the difficult counting task significantly reduced people’s pain intensity scores to thermal stimuli, as well as activity in brain areas that process pain.

The Dynamic Interplay Between Task Load and Emotional Intensity

The above findings illustrate that cognitive tasks can reduce negative feelings because these require mental resources that would otherwise be used for the further processing of negative information. Whereas negative information generally draws a considerable amount of processing resources, strongly negative information has an even stronger impact on people’s mental capacity than mildly negative information (Mogg et al., 2000; Schimmack, 2005, Yuan et al., 2007). For example, people are more likely to ponder over a relationship break-up, than over a broken cup. Therefore, people’s negative emotional states should not only be affected by varying task demands, but also by the intensity of the negative information people encounter. In other words, a person’s momentary feeling state should be the result of the dynamic interplay between cognitive load on the one hand, and the intensity of the emotional trigger on the other hand.

If strongly negative information incorporates more mental resources than mildly negative information, taxing people’s mental capacity with a highly demanding task should reduce people’s emotional responses to strongly negative information to a greater degree than people’s responses to mildly negative information. In support of this reasoning, people only report more intense negative feelings in response to extremely negative images (e.g. mutilated bodies, a famine victim) than in response to mildly negative images (e.g. a crying face, a cockroach on a slice of pizza) when cognitive load of a distracter task is low or absent – i.e. when ample mental resources are available to process the images. When people perform a demanding distracter task, people no longer report more intense negative feelings in response to extremely negative images than in response to mildly negative images (Van Dillen & Koole, 2007).

Some Implications of Emotion’s Limited Resources

The above findings represent a diverse body of research that support the notion that cognitive and emotional processes compete over the same limited mental resources, such that by performing a cognitive task, people can reduce their negative feelings. Although performing a distracter task may thus be an effective tool to deal with negative emotions, it is unlikely to be the ultimate solution to all of people’s emotional problems. That is, distraction reduces the immediate impact of an emotional response, but it leaves the source of this response unaddressed. For example, when Person “B” decides to induce a high mental load on him- or herself by working 70 hours per week in order to deal with the emotional pain as a consequence of Person “A”’s antisocial behavior, the structural cause of their relationship problems remains intact, which makes it likely that the emotional pain will rebound once Person “B” ceases to distract him – or herself. In other words, taxing ones mental resources can be a tool to stop a destructive cycle of negative thoughts dead in it's tracks (Rice, Levine, & Pizarro, 2007), but in the end, distraction is no substitute for problem solving.

One interesting question would be whether taxing people’s processing resources with a demanding task would not only attenuate negative feelings, but also positive feeling states. So far, research has produced somewhat mixed findings on distraction from positive feelings (Erber & Tesser, 1992; Van Dillen & Koole, 2007). This may be because positive feelings operate along different criteria than negative feelings (Isen, 2002). For example, positive feelings are less intrusive, and dissolve more easily than negative feelings (Fiedler, Nickel, Asbeck, & Pagel., 2003), which should make it easier to ‘get rid of’ positive feelings than of negative feelings without having to tax ones mental resources. In fact, because of positive emotions’ free floating properties, people may rather experience difficulties to maintain a positive state.

This may be different for other motivational states such as hunger, fatigue, and sexual desire. Like negative thoughts, cravings (e.g. for food, for sex) have strong intrusive powers, which makes it so hard for people to resist them (Kavanagh, Andrade & May, 2005). Yet, people sometimes forget to eat or drink when they’re deeply involved in a task. Possibly then, a cognitive task may be used as a tool to fight off temptation. Research findings provide some initial support for this idea (Kemps, Tiggemann & Grigg, 2008; Kemps, Tiggemann & Hart, 2004; May, Andrade, Panabokke, & Kavanagh, 2004). For example, people feel fewer cravings for chocolate in response to viewing tasty chocolate pictures, when, subsequently, a rapidly changing screensaver is switched on (Kemps, Tiggemann & Hart, 2004). In a similar vein, smoking-deprived individuals feel less smoking urges when they can watch a game of tennis while they have to wait for an appointment (May, Andrade, Panabokke, & Kavanagh, 2004).

To conclude, the foregoing work proposes that because cognitive processes and emotion processes compete over limited mental resources, people can take the edge of aversive emotional states by engaging in a cognitive task. Importantly, the degree to which people find relief from their negative feelings may depend on the extent to which people tax their mental resources. Thus, mildly dysphoric moods may be regulated by mildly demanding tasks, such as sorting ones mail, or making a grocery list, whereas intensely negative responses call for more fully engaging activities, such as filling out ones tax form, or taking a course of Mandarin Chinese. So in order to make the Mail Goggles even more effective, in addition to the timing of the application, one should also be able to adjust the difficulty of the math problems: mildly complex ones for an average weekend, and mind-boggling math equations for those gloomy nights right after a romantic break-up.

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