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A formal diagnosis of autism involves a trained clinician using professional judgement to match the behaviour and developmental history of a person with relevant diagnostic criteria.
Typically, the criteria used are those in the Diagnostic and Statistical Manual of Mental Disorders (DSM) or the International Classification of Diseases (ICD). Both describe autism in terms of (among many other things) an insistence on routine, sameness, and ritualised behaviours. These traits are part of the current formal definition of autism: They tell us what autistic people do, but they don’t explain why.
I want to suggest a particular way of looking at the autistic insistence on routine, sameness, and ritualised behaviours. Rather than seeing these traits as things that need explaining in themselves, I want to examine the possibility that they are an adaptive strategy: a long-term way of managing the heightened cognitive demands of living as an autistic person in a world that largely reflects non-autistic norms.
The Deficit-Based Model of Autism
Both the DSM and the ICD describe autism in terms of deficits. Language used includes the terms persistent deficits, restricted, repetitive patterns of behaviour, clinically significant impairments, and others in this vein. While the DSM and ICD do not specifically describe insistence on routine, sameness, and ritualised behaviours as deficits, they do use them as diagnostic characteristics of autism. These characteristics are presented within a clinical framework for a neurodevelopmental disorder, so they are generally interpreted as manifestations of impairment rather than as potentially adaptive behaviours.
My suggestion is that these autistic behaviours are not symptoms of autism that require an explanation; they, in fact, are the explanation for something deeper in autism.
Cognitive Load
Cognitive Load Theory comes from the field of cognitive psychology. The theory was developed in the 1980s by Australian psychologist John Sweller. Cognitive load is the effort expended by a person on their working memory; a finite capacity for temporarily holding information used for immediate tasks, including decision-making.
In Sweller’s model, there are three types of cognitive load:
- Intrinsic Cognitive Load: This is the amount of effort required for a specific cognitive task, such as learning a particular language, or performing a specific mathematical calculation.
- Germane Cognitive Load: This is the amount of effort required to process information and transfer it to long-term memory.
- Extraneous Cognitive Load: This is the amount of effort required to deal with the way information is encountered or presented, rather than processing the information itself, for example, information presented as a diagram or verbally.
Mental Exhaustion
For our purposes, the key factor in looking at cognitive load is effort.
Sustained cognitive effort has long been recognised as producing cognitive fatigue. In fact, much work in psychology confirms this. Particularly interesting is a paper by Steward, Looi & Chib (2025), The Neurobiology of Cognitive Fatigue and Its Influence on Effort-Based Choice.
Steward, et al.examined the neuroscience of cognitive fatigue and found that sustained mental effort has measurable effects on a person’s brain and their behaviour. Increases in cognitive demands correlate with increases in subjective mental fatigue, which in turn influences decision-making.
The research showed that when cognitively fatigued, people become less willing to engage in further mentally demanding tasks, even when doing so would be beneficial or rewarding. This process is associated with activity in regions of the brain that are involved in cognitive control and effort evaluation, including the dorsolateral prefrontal cortex and the insula. These findings reinforce the idea that cognitive effort is not an unlimited resource, but one that must be managed over time.
Mental fatigue has measurable physical effects. A 2021 study by Francesco Biondi and colleagues demonstrated that if a higher cognitive load element is added to physical work, increased muscle tension and physical exhaustion can result.
Furthermore, a 2025 study by Habay et al. found that prolonged cognitive effort impaired both cognitive and physical performance, while also increasing participants’ subjective feelings of mental fatigue.
Autistic Cognitive Load
Here, I want to discuss two aspects of autistic experience: Sensory differences and social differences.
Sensory
Various psychological works (for example, Patil et al., 2023) have suggested that autistic sensory experiences are related to differences in sensory gating; an automatic function of the brain that filters out some sensory input so that a person can focus on relevant input. For example, sensory gating might filter out background noises in an office, such as phones ringing and photocopiers whirring, so that you can focus on a conversation with a colleague. It is suggested that a lower threshold of sensory gating might be why autistic people tend to experience a higher sensory load than non-autistic people.
This is not necessarily a global effect. Generally, neurological work in this area has demonstrated differences in neural processing in autistic people: Sometimes the activation might be higher, sometimes lower. But the observation that neural processing issues, including sensory gating, can lead to increased cognitive load in autistic people remains.
Social
Many autistic people report finding social interaction with non-autistic people difficult and tiring. It is common for autistic people to describe needing recovery time, or experiencing “hangover” effects after social events. A 2024 paper by Poulsen et al. discussed this, stating:
“Successful social communication requires awareness of one’s behavior, the reactions, and responses of others, and predicting upcoming events in an interaction. Given the rapid pace of many typical social interactions – particularly face-to-face – these already cognitively challenging mental operations can potentially be overwhelming for autistic people in everyday social settings.” ~How auditory processing influences the autistic profile: A review, Poulsen et al., 2024.
Effects of Mental Exhaustion
Many autistic people report exhaustion from what is often broadly described along the lines of living as an autistic person in a world which is more suited to non-autistic people. The sensory environment in the world is often overwhelming to autistic people, and as we have discussed, increased sensory input, possibly related to sensory gating issues, may be a trigger for this. Social differences also lead to mental exhaustion and overwhelm. Long term, this exhaustion leads to autistic burnout, which is covered in detail in an earlier article on this website.
Unconscious Behavioural Optimisation
Human beings tend to behave in ways that minimise cost and maximise efficiency. In this context, cost refers to effort and cognitive load. Sometimes people consciously adopt routines that reduce the need to make further decisions later, so they can concentrate their mental effort elsewhere. Former US President Barack Obama famously wore the same suit for eight years, according to his wife, saying that it reduced decision fatigue. Similar claims have been made about the late Steve Jobs, co-founder of Apple Inc.
A routine is, in effect, a decision that only has to be made once. Choosing the same breakfast every morning, taking the same route to work, or following the same bedtime routine removes the need to repeatedly evaluate alternatives. Each individual saving is small, but together they reduce the number of decisions that must be made each day. For anyone living with finite cognitive resources, this is an efficient strategy.
However, this routine-building behaviour is often done unconsciously. Human beings naturally develop habits and routines that make everyday life more efficient. Many of these behaviours emerge gradually through repetition because they reduce effort, increase predictability, or produce more successful outcomes, rather than because people consciously decide to optimise their behaviour. This idea is found in many areas of psychology, notably the concept of implicit learning; gradually learning without being consciously aware of it. .
Autistic Routine as an Adaptive Resource-Management Strategy
We have seen that human beings have a finite capacity for cognitive effort. Each activity we undertake and everything we process from our environment adds to our cognitive load.
The long-term effects of high cognitive load can be detrimental to well-being.
Human beings tend to adopt routines in life to take the path of least cognitive effort.
Autistic people may experience greater cognitive demands due to differences in sensory and social processing.
If autistic people routinely experience greater cognitive demands because of differences in sensory and social processing, it follows that behaviours which reduce unnecessary cognitive effort would be especially valuable.
Routine, sameness and ritualised behaviours may function as an adaptive strategy for managing finite cognitive resources by reducing the need to repeatedly make everyday decisions. Over time, such behaviours could become established through implicit learning because they consistently reduce cognitive demands.
This reliance on routine, sameness, and ritualised behaviours could well be developed unconsciously over time, although, anecdotally, many autistic adults consciously recognise the benefits of routine and predictability, and find comfort in it.
If this hypothesis is correct, then insistence on routine, sameness and ritualised behaviour need not be understood solely as diagnostic characteristics. They may also represent adaptive strategies that help autistic people manage finite cognitive resources in an environment that often places unusually high cognitive demands upon them.
Whether this hypothesis ultimately proves to be correct is a question for future research. However, it offers a different way of understanding behaviours that have traditionally been viewed only through a diagnostic lens. Rather than asking why autistic people insist on routine, sameness and ritualised behaviours, perhaps we should also ask what those behaviours achieve.
That’s all for this time. Take care.
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