Automatic Behavioural Responses: Why we Overeat

Eating decisions are connected and influenced by a variety of factors, both internal (that is, unconscious behaviours) and external, which can all lead us to increased caloric consumption and poor dietary choices.

INTERNAL FACTORS include self-control and ego depletion. Researchers have demonstrated that willpower is a finite resource, that is, mental resources are not infinite and need to be periodically replenished. Humans are vulnerable to the biologic phenomenon of ego depletion (Baumeister et al., 1988), a state of decrement in functioning, in which the self is impaired in the regulation of behaviour.  The brain consumes more glucose than other parts of the body, and factors such as intense cognitive activities; the maintenance of self-control or the inhibition of emotional reactions; the control of obsessive thoughts; all participate in the reduction of the levels of motivation and self-control. Ego depletion can lead to a lesser degree of mental clarity and attentiveness, a poorer ability to complete a task, or an increased difficulty in resisting temptation. Hence, when we are in a state of ego depletion, we may be more irritable, we may react more aggressively, or we may fail in sticking to a diet, and indulge in junk food.


The existence of ego depletion, highlights that internal resources available to the self to make choices and exert self-control are limited, and this may explain why automatic responses exist (Baumeister et al, 1998). In fact, when we behave in an automatic, intuitive mode, we function using less resources. This happens when we drive after years of practice, when we cook the usual meal, or when we stop before crossing the road to check if a car is arriving. We do all these actions automatically, without the need to think about the action itself. 

EXTERNAL FACTORS on the other hand, include contextual cues and priming. Researchers now recognise that dietary behaviours are largely the product of responses that are automatically activated when the individual is exposed to food cues. Priming refers to a phenomenon of so-called associative activation, in which the exposure to a certain stimulus, activates in our mind associated ideas. For instance, if I expose you to the word EAT, you are more likely to complete the fragment: SO_P

…with the word SOUP, rather than SOAP. Because you were primed with a concept – the word eat – that generated associated ideas in your mind. The opposite would have happened if you were primed with the word WASH.

Priming and contextual cues are the reason why we are so influenced when we are in a restaurant, in a cafeteria, or simply walking on the streets passing by shops selling food. A multiplicity of sensory stimuli capture our senses, and influence our behaviour. This ranges from the shape and size of a portion; the behaviour of the people sitting at our table; the behaviour of the waitress; the music; the design of the ambient; all play a role on perception and behaviour. In the same way, calorie labels, labelling food as ‘natural’ or ‘healthy’, influence perception, thus choice.

Indeed, all these unconscious behavioural influences and the presence of infinite environmental stimuli does not make us defenceless. We are equipped with selective attention, self-control, and rational, deliberative thinking. But conscious forces work along with unconscious forces, and sometimes, even against our best will, we fail. This has implications for everybody, but mostly, it shows how difficult it is for overweight people, and people with bulimic disorders, to deal with themselves when it comes to food choices. It is not always up to the individual, because will power is not infinite. Therefore people who successfully manages to lose weight, or to get free from a compulsive eating disorders, deserve big congratulations.