Introduction

In this article, we explore the theory behind complex systems to better understand the key differences between them and complicated systems. Distinguishing between the two is important because to intervene in said systems for positive change, each system requires a different approach, where systems thinking and understanding are essential. A complex system is a concept that refers to systems such as society, the weather or human consciousness. They are made up of many interactive elements whose relationships vary and are often difficult to predict outcomes. Complex systems are more than the sum of their parts, meaning that by breaking them down to just those independent components, we can’t always predict how they will change or react based on those components and their interactions alone [1]. This article explores key differences between complex and complicated systems, such as non-linearity and a lack of clear cause-and-effect relationships [1]. The other key aspect discussed in this article is emergence, the result of self-organisation and feedback loops. When the components of the complex system are looked at in their interactions with each other, the feedback loops they create, and the self-organising behaviour they display, we can begin to understand another feature of a complex system, emergence [2]. Emergent behaviour can’t be predicted by studying the elements alone; it must be approached from a complex systems mindset in order to take into account how these interactions result in new behaviours.

Non-Linearity and Cause and Effect

One of the key aspects that differentiates a complex versus a complicated system is their relationship with cause and effect [1], [3]. In a complicated system, this tends to be a linear relationship. If one of the parts making up the system fails, we have a strong enough understanding of how this change will affect the rest of the system. For example, if the motor of a car doesn’t start, the car won’t go.

This same predictability is much more difficult in complex systems. Society is a good example of a complex system, and an example of this is Greta Thunberg. Unlike a car’s motor not starting, no one could have predicted that a 15-year-old’s protest outside the Swedish parliament would have sparked a global shift in attention, unprecedented access and opportunities to speak to delegates and multiple speeches at some of the highest levels to fight for climate change [4]. This was not a linear relationship, not a clear case of cause and effect, and no one could have predicted her impact on the fight for climate change based on examining her protest outside the parliament alone. This demonstrates how different complex systems are from complicated ones in terms of linearity and predictability [3].

Emergence

Emergence is the result of the interaction and relationships between different components of a complex system, and how those results then interact and influence each other [2]–[3]. When emergence appears in complicated systems, it is normally predictable and easier to trace back to a source or interaction of component parts. An example of this is the sound of an engine. Often, luxury cars have specific sounds, but originally this came from the interaction between independent components of the car itself, before the sounds were recognised as desirable and traced back to the specific parts and their interactions were examined until they were repeatable.

For complex systems, consciousness is an excellent example and the one that will be explored in further depth later in the article. We don’t fully understand where consciousness comes from, though we seem almost certain that it arises from another system, the brain. But many species have brains, and not all have the highly developed form of consciousness present in humans, though they show self-awareness.

Complicated: Human Digestive System

Most of us are familiar with the digestive system. Food goes in the mouth, down the throat, into the stomach, where it is digested. However, while we can describe the outcome of the system (digestion of food) and a vague overview of the process, unless we study it in more detail, it is unlikely that we can articulate the complicated structure of the digestive system further without more research. This is because it is a complicated system, where, upon further research, we can come to understand the goals, processes and elements of the system with a little extra work. This is because linear causeand-effect relationships are taught early on in life, typically, good behaviour results in rewards, and bad behaviour results in punishments. To briefly touch upon something discussed later in the article, complex systems do not have such clear relationships and require a shift in mindset to understand, rather than additional research to comprehend the system.

A more detailed description of this system is food beginning in the mouth, being broken down by your teeth before travelling down the oesophagus into the stomach [5]. Here, the liver releases bile to help the stomach break down food [5]. Travelling into the small intestine, the pancreas releases enzymes to break down the proteins, lipids and carbohydrates from the food [5]. Food which can’t be broken down moves to the large intestine before being passed into the rectum, where it will be expelled through the final part of the digestive system, the anus [5].

The reason this is a complicated system, not a complex one, is that it lacks some of the key factors we use to define a complex system. The digestive system has a clear purpose: to digest food. There are not many options to deviate from this goal unless something goes wrong, and when we look at the parts in isolation, we can clearly see their purpose and role in the digestive system. For example, the oesophagus. In the digestive system, its role is to transport the chewed food from the mouth to the stomach, and when looked at in isolation, we know that that’s its role. There is a stability to this system; nothing new or unexpected emerges from the relationships between these elements, there is no self-organising behaviour displayed and thus no emergence [2]–[3].

Complex: Human Consciousness

Complex systems are often much harder to understand and predict than a complicated system, and to exemplify this, we consider the human consciousness. A nebulous concept, we are still working to understand this complex system. We cannot attribute consciousness to any one thing, not a specific gene or series of genes, not a location or function in the brain and not even determine the exact neural pathways that we can definitively say form a key element of the complex system that is our consciousness [7].

When looking at linearity, there’s no clear cause and effect, suggesting that human consciousness is non-linear. Where in the examination of the brain or other biological systems there is a clear theory that is developed on where to research next - whether it is a genetic disease being narrowed down to a specific chromosome or which cells need to be targeted to fight cancer, the fundamental theory behind consciousness in humans is not nearly so clear or easily narrowed down to something specific in the body outside our key organ, the brain [7]. We don’t have the information to understand the whys or hows of this complex system, let alone have enough expertise on the relationships between the parts to intervene in key areas with a relatively safe range of predicted results. However, as our understanding of key differences between complex and complicated systems grows, we can begin to understand with more ease why a new mindset is needed, and how we can dissect complex system interactions so we can begin to make positive change.

One of the strongest pieces of evidence for human consciousness being a complex system is the theory of emergence. We know and are exploring further every day the aspects of the brain, which areas contribute to logical reasoning and emotional processing [7]. Which chemicals incite which reaction to isolate particular neurotransmitters or which hormones to understand what causes moods or decisions? However, we haven’t yet pinpointed what allows us to understand abstract concepts such as the self. This is a clear example of emergence, of multiple components interacting and creating new behaviour that cannot be easily predicted through examination of the elements in isolation [2].

Conclusion:

In our exploration of complex and complicated systems, we have highlighted two of the key differences between them: emergence and non-linearity. In a complicated system, such as the digestive system, the parts can be examined in isolation and their roles in the system understood to the point where we can make accurate predictions based on them. In a complex system, however, this is not as easily done, and often the relationships and results of interactions between the components form new and unique results that couldn’t have been predicted, and are more than the sum of the parts of the system. This emergent behaviour is an essential difference that requires systems thinking when considering making an intervention in such a complex system. By understanding the differences between these systems, we can redefine our approach to intervening for positive change in complex systems, shifting into a systems thinking mindset in order to better understand and make more effective strategies.