The Effects of Calorie Restriction and Calorie Restriction Odour on Aggressive Social Behaviour in Male Rats

Introduction

1.1 Background

In Australian society, there is a current concern relating to aggression and violence. Although crime rates are decreasing, there is a recent rise in the amount of aggravated assaults (Australian Institute of Criminology, 2008; Crime Statistics Agency, 2018). This burden is causing psychological and physical injuries to people within the community (Australian Institute of Criminology, 2008). This issue comes at great cost to emergency services to assist with these incidents, as well as ongoing expenses related to victims of crime, with an average cost $1,700 per assault (Australian institute of criminology, 2008; Mayhew, 2003). This issue is also affecting Australian health care worker with the amount of aggressive and violence behaviour from patients (Amies, 2016). Paramedics and nurses are also falling victim to aggressive and violence patients on a regular basis, and on average one paramedic is assaulted every 50 hours in the Victoria (Ambulance Victoria, 2018). The Health Minister is working consistently on plans to protect our health care worker and reduce this type of behaviour being allowed to continue (Amies, 2016). The Australian government is working together with police to uphold the community safety statement 2018/2019 which has been impacted by aggressive and violent acts (Premier of Victoria, 2018). A more comprehensive understanding of aggression and violent behaviour, would lead to improvements in intervention and prevention strategies.

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1.2 Aggressive Behaviour

The term Aggression is frequently used and sometimes misunderstood for hostility, anger or competitiveness (Warburton & Anderson, 2015). Warburton and Anderson (2015) explain aggressive behaviour as any behaviour intended to cause harm to another who is motivated to avoid harm. Aggression is seen to be displayed in different forms; verbally, passively and physically; such as hitting or fighting (Warburton & Anderson, 2015). Aggressive behaviour research, in the past has looked into explanations for aggressive behaviour through underlying biological factors, environmental risk factors/triggers, neurocognitive and psychological process (Warburton & Anderson, 2015). There has been a multidisciplinary approach in past research on aggression to assist with a further understanding of what drives this behaviour to educate intervention and prevention strategies.

From an evolutionary perspective, aggressive behaviour is expressed as a protective behaviour of resources; food and reproduction to fend off competition and increase survival. (Warburton & Anderson, 2015). Aggression has been looked at from a biological stand point where research has been conducted on the impact of; genetic, epigenetics, hormones, pre-disposition and malformation/damage (Warburton & Anderson, 2015). Further to these biological factors, social psychologist have looked deeper in personality factors and individual differences in level of aggression. Looking at aggressive behaviour from a learning and environmental influence, researchers have explained aggressive behaviour as something that is influenced by experience and surroundings (Warburton & Anderson, 2015). There is limited research conducted aggressive and dominant behaviours being affected by diet composition and regime. Most research in this area is focused on assessing positive effect such as lowering anxiety like behaviours (Govic, et al., 2009; Guccione, Paolini, Penman & Djouma, 2012; Kenny, Dinan, Cai, Spencer, 2014; Levay et al., 2007)

In past research there has been investigation of not only the display of aggression, but what some of the underlying influences of this behaviour. Previous research has identified that aggression can been influenced by frustration (Warburton & Anderson, 2015). This frustration could be the result of issues within cognitive functioning or a stressful situation, being triggered by a stimulus or situation which is provoking of the aggressive behaviour (Warburton & Anderson, 2015). Antisocial behaviour, such as aggression and violence has also been showed to be learned by experience, through the social learning theory (Warburton & Anderson, 2015). The classic example where aggressive behaviour is demonstrated after a learning task, watching aggressive and violent act is Bandura's bobo doll experiment (Liu, 2006; Warburton & Anderson, 2015). This experiment showed children replicated the aggressive behaviours they had watched on a recording of another person being aggressive towards a blow up toy (Liu, 2006). Liu (2006) extends on from this idea of social learning and explains aggressive behaviour to be influenced by physical surrounding and display in media. If exposed to aggression and violence within their community or in the media can influence the person watching to become more aggressive, increasing the serious threat of aggression to society (Liu, 2006; Warburton & Anderson, 2015).

1.3 Dominance Behaviour

Dominance is a behaviour that is commonly associated with aggressive behaviour, whereby a human or animal seeks to overpower another (Kaufmann, 1983). Within an evolutionary setting, those with greater access to resources are those that are more dominant when resources are in short supply (Kaufmann, 1983). Dominance is increased when there is a sense of territoriality, defending their 'space' or their environment, in which they have developed attachment to as their resource storage and home base (Kaufmann, 1983). This knowledge of territoriality has informed researcher on tests that can use this to elicit aggressive and dominant behaviour to enable measurements of these behaviours between groups (Kaufmann, 1983).

Aggression is not a standalone behaviour and has been shown to be associated closely with dominance and anxiety (Patki, Atrooz, Alkadhi, Solanki & Salim, 2015). It has been found that when stress related anxiety is heightened so was the levels of aggression displayed in rats (Patki et al., 2015). Dominance has also been found to correlate with aggression in studies concerning mammals (Stamps, 1999; Muller & Wrangham, 2004). Mammals have a tendency to act in an aggressive way to defend their territory or status within a group to control their status within the group. Within the animal kingdom there is a linear dominance hierarchy, this is a pecking order of the animal based on level of dominance (Muller & Wrangham, 2004). The top of the hierarchy is referred to the alpha and is constantly required to express aggressive behaviour through antagonistic encounter from other animals trying to overpower and take the position as the alpha. (Stamps, 1999; Muller & Wrangham, 2004). Dominance and aggression is critical in survival and resources in nonhuman mammals.

1.4 Animal Models of Aggression and Dominance

There has been a variety of models developed to enable testing of various behaviours within rodents and other mammals (Conn & Jha, 2013; Govic et al., 2008; Govic et al., 2009; Guccione et al., 2012; Kaidanovich-Beilin, Lipina, Vukobradovic, Roder, & Woodgett, 2011; Lutter, et al., 2008). For instance, anxiety-like behaviour is commonly tested utilising the open field test and elevated plus maze test. (Conn & Jha, 2013). With respect to the assessment of aggression and dominance,...