Decision-making is a continuous brain process that we are generally unaware off, until our choices result in unpredicted consequences. We may recall and wonder, ‘Why did I choose that option? Was it conscious or subconscious? Was I emotionally influenced?’ In recent years, neuroscientists have begun to decrypt our decision- making processes. What they are learning is shedding light not only on how a healthy brain performs complex mental functions, but also how disorders such as drug abuse can affect the process. Our decisions are what make us who we are, and the consequences of our decisions affect what happens throughout our lives and who we become.
A number of brain structures, including the anterior cingulate cortex, orbitofrontal cortex and the overlapping ventromedial prefrontal cortex are thought to be involved in decision-making processes. In these different brain regions, studies indicate that decisions result from rapid multifaceted probability calculations within the brains neurons.
It would not be unusual to imagine that successful decision making relies on the rational frontal lobes of the brain, and not from the emotional areas of the brain such as the limbic system which is found deeper in the brain. However, studies have shown emotions to aid in decision-making processes.
Decision-making often occurs in the face of uncertainty, situations when our choices will lead to benefit or harm. The emotional input provides the brain with motivation and meaning which are essential for effective decision making. The limbic system, made up of the hypothalamus, the hippocampus and the amygdala (see diagram), is responsible for emotional responses. Studies have shown that people who have experienced damage to parts of their limbic system are no longer capable of making decisions, as their rational mind hesitates cyclically over the possible rational reasons for each course of action.
Conversely, people who experience damage on the rational frontal lobes of their brain were still capable of making decisions. Scientists from the University of Maryland monitored the micro patterns of activity in the frontopolar cortex of several participants. The results indicated they could predict each participant’s decision up to seven seconds before the participant themselves became aware of their decision. Thus, humans typically make their decisions irrationally. However when a decision goes wrong and things don’t turn out as predicted, the orbitofrontal cortex helps us change our behaviour by responding to our mistakes. This finding can also be linked to a study which found cocaine addicts who often exhibit damage to their orbitofrontal cortex, frequently not being able to weigh up the rewards of drug use against the costs.
Memory is another key factor of decision- making. The decisions we make are greatly influenced by our mood which works as ‘a retrieval cue’ whereby negative feelings make negative materials come to mind, which in turn have great impacts on the decisions we make. The same is true for positive feelings. In 1981, G. H. Bower termed this phenomenon ‘state-dependent remembering’. Bower and his colleagues specified that feelings and emotions cannot be removed from the human mind. The emotions felt in specific circumstances will be recorded in the emotional memory, and can be triggered when a person faces a difficult decision over a short period of time. In these situations the decision-maker is usually unaware of previous experiences in similar past situations influencing their current situation.
The fact that most of our decisions and actions depend on 95% of brain activity beyond our conscious awareness, means that 95 – 99% of our life derives from the programming in our subconscious mind. Our subconscious controls what we do and who we are; now that really is something to think about.
Angelina Chrysanthou is studying for an MSc in Molecular Medicine.
Images: Decision making by Nerovivo (Flickr); Limbic system diagram by Kate Whittington