Motivation and emotion/Book/2015/Hanger

Overview
''Have you ever lashed out in anger when you're hungry? Do you have trouble controlling aggressive impulses when you haven't eaten? Does your partner, family, or close friend know to give you food when you start acting irritably? Does quickly scoffing down a snack transform you from an angry monster into your normal, pleasant self?''

The behaviour described above has attracted the term ‘hangry’ and, as it turns out, there is a scientific explanation for this phenomenon (Bushman et al., 2014). Hanger (pronounced han/ger) refers to the phenomenon of experiencing anger, or other negative emotional states such as irritability or frustration, when you are hungry (Oxford University Press, 2015). The term 'hangry', an amalgam of hungry and angry, is a newly invented word that has recently been added to the Oxford English Dictionary (Sami, 2015). People sometimes experience hanger when they haven't consumed enough food, they do not metabolise glucose effectively, or consume foods that result in blood sugar spikes (DeWall, Deckman, Gailliot, & Bushman, 2011; Benton, 2002).

In recent years, significant research has been conducted on the science behind hanger (DeWall et al., 2011; Bushman et al., 2014). Multiple researchers have found that when glucose levels are low, the brain lacks the energy required for self-control and self-regulation, resulting in episodes of aggression or other socially inappropriate behaviours (Benton, 2002; see Willpower). Moreover, literature suggests that individuals suffering from Seasonal Affective Disorder (SAD) and premenstrual syndrome (PMS) eat high-carbohydrate foods for a psychopharmacologic effect, indicating that food can be used to improve mood (Benton & Nabb, 2003).

This chapter describes the internal processes that cause hanger, how hanger manifests, and offers suggestions for handling anger caused by hunger.

The Brain & Energy
The human brain requires an extremely large amount of energy to function. When the body is at rest, the brain accounts for 20 to 30% of its total energy use, oxidising approximately 120g of glucose daily (Benton & Nabb, 2003; Owen & Sunram-Lea, 2011). This is despite the fact the brain comprises only 2% of a person's body weight. The energy required by the body and brain is derived from nutritious food intake, which is broken down into glycogen and converted into glucose (DeWall, et al., 2011). Glucose is the primary energy source for the brain, and neutrons require a constant supply from the bloodstream (Mergenthaler, Lindauer, Dienel & Meisel, 2013). Glucose is the precursor for neurotransmitter synthesis and ATP, the cellular energy-carrying molecule (Mergenthaler et al., 2013; Owen & Sunram-Lea, 2011). Thus, insufficient energy or carbohydrate in the diet can lead to low blood glucose, resulting in insufficient fuel for the brain to function efficiently. Without renewal, the brain's energy stores would be depleted within 10 minutes (Donohoe & Benton, 1999). Compared to other bodily organs, the brain is highly sensitive to alternations in its energy supply (Owen & Sunram-Lea, 2011). Blood glucose below 40mg/100mL (known as hypoglycaemia) results in discomfort, confusion, coma, convulsions, or even death (Owen & Sunram-Lea, 2011). The brain's reliance on glucose for energy stems from selective permeability of the blood-brain barrier (BBB): under normal circumstances glucose is the only fuel permitted to pass. Under extreme circumstances, such as during strenuous physical activity or starvation, ketone bodies are released that can cross the BBB to supply the brain with energy (Mergenthaler et al., 2013).



Through positron emission tomography (PET) scans, researchers have established a positive association between increased mental activity and glucose metabolism (Benton & Nabb, 2003). Within minutes of eating, blood-glucose is metabolised in areas of the brain specifically used for higher-cognitive tasks. Thus, cognitive tasks deplete energy; with more difficult tasks placing greater metabolic-demand on the brain. Perhaps not surprisingly then, glucose consumption can improve cognitive functioning. Glucose demonstrates an inverted-U shape effect on cognitive functioning, with 25g being the optimal dosage to improve memory in adults (Owen & Sunram-Lea, 2011). Most pronounced gains appear in tasks of verbal declarative memory (i.e. those involving high cognitive demand), which involve hippocampal brain regions (Owen & Sunram-Lea, 2011). While glucose-rich carbohydrates provide short-term energy-boost, the accompanying release of insulin results in a lowering of blood glucose. Low blood glucose has been linked to changes in relative mood, and a tendency to become irritable and aggressive (Benton, 2002).

Aggression
Aggression and violence originally developed as adaptive behaviour in humans and have existed since time immemorial (DeWall, Finkel, & Denson, 2011; DeWall, Anderson, & Bushman, 2011). Aggression has played an important role in mate selection, protection, and survival. However, as humans have developed socially and culturally, serious forms of aggression have become more maladaptive than adaptive, especially on social and interpersonal levels (DeWall et al., 2011a). Aggressive tendencies differ from person-to-person and are influenced by their genetic makeup, as well as their culture and situational context (DeWall et al., 2011c). Aggression manifests in society in myriad forms; through intimate partner violence, group violence, between individuals that know one another, and also between strangers (DeWall et al., 2011a).

I3 Theory
I3 theory (pronounced ‘I-cubed theory’) is a meta-theory of aggression that has been developed as an integrative framework that links theoretical understandings of aggression and self-control (Denson, DeWall & Finkel, 2012). According to I3 theory, three processes (the three Is) underlie aggression: instigation, impellance, and inhibition (DeWall, et al, 2011c). Instigation refers to provocation: discrete social dynamics between a person and a potential victim, such as insults or rejection, trigger an urge to aggress. Impellance refers to trait aggressiveness: a person is psychologically prepared, based on dispositional or situational factors, to respond with a strong urge to aggress when encountering certain circumstances, such as physical pain or dispositional anger. If instigation and impellance are strong, the urge to aggress is most powerful (Denson et al., 2012). Lastly, inhibition refers to self-control: a person is likely to override an aggressive urge depending on dispositional or situational factors. As summarised by Denson et al., if inhibition is stronger than instigation and impellance, people behave non-aggressively. Conversely, aggressive behaviour occurs when inhibition is weaker than instigation and impellance (Denson et al., 2012; DeWall et al, 2011c). This understanding of aggression and self-control can be applied broadly to hanger and its connection to self-control, which will be explored in more detail in the following sections.

Self-Control and Anger
Most, if not all, people experience some form of anger or provocation on a relatively regular basis (DeWall et al., 2011b). However, in many instances, anger is not acted upon because behaviour is effectively maintained by self-control. Self-control refers to the ability to overcome urges, impulses, habitual behaviour, and desires (Bushman et al., 2014). It is a conscious and effortful form of self-regulation that is fundamental to social human behaviour due to its ability to align emotions, thoughts, and behaviours with personal or social expectations and norms (Gailliot & Baumeister, 2007). Recent research in the field of psychology has linked poor self-control and self-regulation to aggressive and violent behaviour (Denson et al., 2012). While there are many causes for aggression and violence (DeWall et al., 2011), Denson et al. (2012) found that a failure in self-control can cause people to act aggressively in situations where it is personally or socially inappropriate. Exercising self-control and self-regulation requires significant energy from the brain and therefore is considered a limited resource (DeWall et al., 2011). The idea that self-control is limited by energy is explained in ego depletion theory. Ego depletion theory asserts that a person's capacity for exercising self-control is depleted with exertion. By using self-control for one activity, self-control is diminished for a subsequent activity. This results in decreased self-control at times of depletion, which can only be restored by rest or energy intake, and explains why people have temporary lapses in their self-control (Denson et al., 2012).

The Brain and Self-Control
The ability to override aggressive urges comes from the brain (Denson et al., 2012). More specifically, neuroscientific research has suggested that anger and aggressive urges are controlled in the prefrontal cortical regions of the brain, namely the orbitofrontal cortex, anterior cingulate cortex, medial prefrontal cortex, and dorsal and ventral lateral prefrontal cortex. Self-regulation, and thus self-control, as well as emotion regulation are broadly supported by these areas (Heatherton & Wagner, 2011). According to Heatherton and Wagner, strong impulses have the potential to overwhelm the prefrontal cortex, resulting in a reliance on subcortical areas of the brain, which diminishes self-regulatory systems. From this, it can be seen that self-regulation is cognitively demanding and requires significant energy from multiple cortical regions.



Blood Glucose Levels and Self-Control
The energy needed for self-regulation and self-control comes by way of glucose in the bloodstream (DeWall et al., 2011). As we have already seen, glucose provides a vital source of energy to the brain and is therefore imperative to all cognitive processes. Numerous studies have found that blood glucose levels affect a persons' ability to maintain self-control (Denson et al., 2012; DeWall et al., 2011b; Gailliot & Baumeister, 2007). Moreover, low blood glucose concentration has been associated with poorer attention, difficulty regulating emotions, and even increases in violent and criminal behaviour (Bushman et al., 2014; DeWall et al., 2011b). Interestingly, glucose metabolism becomes less efficient throughout the day (as seen in Figure 2.). This decline in blood glucose concentration has been linked with poorer mood and higher rates of aggression in the evening (Bushman et al., 2014). Due to the cognitive process involved, self-control is thought to be metabolically expensive. That is, it requires a significant amount of energy, which is provided by blood glucose. Understanding this can help to explain ego depletion theory and why self-control is a finite resource.

Studies of Particular Interest to Hanger
There are two studies that are of particular relevance to the hangry phenomenon. The first study was completed by DeWall, Deckman, Gailliot, and Bushman in 2011. The purpose of this study was to determine if there is a causal link between low blood glucose concentration and high aggression levels. Participants were randomly provided with either a sugar containing beverage, or a placebo beverage that tasted sweet but contained no glucose. Afterward, when playing a competitive reaction time task designed to measure aggressive behaviour, participants who had consumed the placebo beverage were more likely to blast their ostensible partner with a loud noise, indicating aggressive behaviour. As predicted, participants who had consumed glucose were less likely to exhibit aggressive behaviour toward their randomly assigned partner. The second study, by Bushman, DeWall, Pond, and Hanus in 2014, was considerably larger and sought to further the findings of the 2011 study. In this experiment, the researchers aimed to determine if evening blood glucose concentrations could predict aggressive impulses and behaviour between married couples. Over 21 days, participants were required to stick between 0 and 51 pins in a voodoo doll representing their spouse, indicating their aggressive impulses toward their partner, as well as recording their blood glucose levels. Like the 2011 experiment, couples also competed in a competitive reaction time task and blasted each other with loud noises. Again, it was found that lower blood glucose concentrations were connected with increased aggression, with the reverse being true of high glucose levels.

What is the significance?
The study by DeWall et al. (2011b) is significant as it was the first of it's kind to find that increased blood sugar levels can reduce instances of aggressive behaviour, or rather, it indicated that hanger does indeed occur. Interestingly, it also demonstrated that anger caused by low blood glucose can be acted out between strangers, which has implications in the social sphere. The 2014 study has even greater implications as the findings can be extended to understandings of intimate partner violence and quarrels that have damaging consequences on relationships (Bushman et al., 2014). According to Bushman et al., individuals are most often aggressive to the people they are closest to. The idea that intimate partner relationships can be adversely affected by lowered blood glucose concentrations is supported by studies of depleted self-control and aggressive behaviour between intimate partners. Researchers have found that when depleted of self-control, intimate partners are more likely to be provoked by their partner and behave aggressively towards them (Denson et al., 2012). In sum, researchers have established a causal relationship between blood-glucose concentrations and aggressive behaviour, providing evidence for hanger. Moreover, it can be seen that hanger can potentially have negative consequences on interpersonal relationships.

Monitoring Food Intake
The best way to manage hanger is to eat at regular intervals. This prevents low blood glucose levels that result in diminished self-control and outbursts of anger. When food is not consumed, blood glucose concentration slowly declines throughout the day until hunger is triggered (Ciampolini et al., 2010). An important factor in controlling hanger is to recognise initial hunger that indicates a decline in blood glucose. According to Ciampolini et al., initial hunger is the beginning stages of hunger that occur before prolonged hunger is experienced (such as gastric pangs, sensations of emptiness, and mental or physical weakness). The ability to recognise initial hunger is associated with important physiological regulation of energy needs as it provides meal-by-meal feedback that allows a person to optimise their food intake.

Type of Food


Food products may affect cognition differently, due to differences in the rate of glucose delivery to the blood. The glycaemic index (GI) of food was developed as a means to compare the physiological effect different carbohydrate-containing foods have on an individual’s blood sugar levels (Png, Bhaskaran, Sinclair & Aziz, 2014). Low-GI foods result in moderate release of glucose to the blood, and thus maintain prolonged glucose supply to the brain, above fasting concentrations (Nilsson, Radeborg & Bjorck, 2012). In contrast, foods with a high-GI value are rapidly digested and absorbed, resulting in considerable fluctuations in blood glucose concentrations (Png, Bhaskaran, Sinclair & Aziz, 2014). Most notably, high-GI food is characterised by a rapid and high peak in blood glucose concentrations, followed by a sharp decline, whereas low-GI foods are characterised by a low peak in blood glucose concentrations and a slower decline (Lamport, Hoyle, Lawton, Mansfield & Dye, 2011). From this it can be inferred that high-GI foods may be effective at reducing immediate feelings of hunger and mediating declining self-control. However, they will not provide enduring energy between meals. Conversely, low-GI foods are considerably more effective at providing a sustained energy release between meals and stabilising blood glucose levels for a prolonged period and therefore are conducive to reducing hanger and maintaining self-control.

Increasing Self-Control
As discussed, poor self-control is thought to be a leading cause for hanger. Thus increasing self-control is one method for reducing 'hangry' occurrences. Researchers have found that self-control can be increased by practicing it over time, in much the same way that a muscle can be strengthened with dedicated training (Denson et al., 2012). This is referred to as the bolstering hypothesis, whereby increasing self-control reduces aggression. In one study, researchers found that participants with high trait-aggression were less likely to react aggressively to provocation if they had used their non-dominant hand (thus exercising self-control) in everyday tasks for two weeks (Denson, Capper, Oaten, Friese & Schofielf, 2011). Alternatively, an additional method for increasing self-control is via acute sugar consumption. Studies have shown that participants with high trait aggressiveness were less likely to react to provocation if they had consumed a sugary beverage that bolstered their blood glucose levels (Denson et al., 2011). In sum, aggressive individuals can monitor their self-control by actively engaging in self-control tasks for an extended period of time, or by consuming food that increases their blood glucose concentration.

Conclusion
While the phrase 'hangry' is a relatively new development in modern language, the physiological reasoning behind it has been explored by academics and scientists for many years. Based on the available literature, it can be seen that hanger arises from an interplay of low blood glucose concentrations, diminished self-control, and situational factors. While recent research has provided important insights into hanger and how it manifests on an interpersonal level, more research is required to understand how prevalent hanger is, and the effect it has on society more broadly.

If you think you suffer from hanger, it is important to understand this tendency and apply techniques to mitigate your aggressive symptoms when blood glucose levels are low. Conversely, you may be able to sneak a muesli bar to your partner when you notice early signs of hanger!

Quiz
{What is hanger? -When bae is grumpy +Experiencing anger when you're hungry -When you really want a cheese burger but there is a queue -A coat hanger
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{What causes hanger? -An annoying person -Your partner's voodoo doll +Low blood glucose levels and a loss of self-control -High blood glucose levels
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{Which naturally occurring compound provides energy for the body and brain? +Glucose -Glycogen -Bananas -ATP
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{How can hanger be prevented? -Eating regularly -Practicing self-control -Consuming healthy, low-GI foods +All of the above
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