We usually consider inertia to be both a problem getting started and a problem with stopping. My research needs to be a bit narrower, so I'm focusing mainly on difficulties getting started, which I've taken to calling initiation impairments, at least for now. Even that is quite broad, and I'm actually only interested in one aspect of it (number 5 below), but to begin with I have to approach the topic more broadly because no one has written anything coherent about it before. So I started with a review of the research literature about autism and initiation. From that, I have started to structure what is already known about initiation impairments in autism.
Inertia, like so many autistic traits, including autism itself, appears to be a number of different things that have related appearances but different mechanisms. Many autistic people will have more than one of these mechanisms contributing to their inertia. The ways research has looked at autism and initiation so far can be fit into these categories:
1. Initiation as an aspect of social interaction
That is, they discuss, or measure, social initiation. Most often, they don't even see difficulty with social initiation as an initiation problem, it's that autistic people (exclusively children) don't initiate because of a primary deficit in social interaction. They usually see initiation of interaction as a convenient way of measuring sociability and whether it has changed due to intervention.
2. Initiation as an aspect of emotion (mental health problems and/or motivation)
This view is that autistic people are unmotivated - or specifically socially unmotivated - which may be due to depression. Alternatively, high levels of anxiety, which we know are common in autistic people, cause a kind of action paralysis where the person is fairly literally 'scared stiff'. No move is the right one, and anxiety about what the anticipated action prevents them being able to act. (This is the only interpretation of 'inertia' acknowledged in the Wikipedia article on the subject.)
3. Initiation as an aspect of attention control
There is a lot of evidence - and a lot of conflicting evidence - that autistic people have difficulty with disengaging attention, particularly visual attention. This is probably part of why autistics get hyperfocussed and 'stuck in' to what they're doing, for better or for worse. This is also called 'monotropism' as a general theory of autistic cognition.
4. Initiation as an aspect of executive function
This is the most common way for those who understand and acknowledge inertia to see the phenomenon. Initiative is a part of executive function, although in that context it is combined with planning and prioritising complex tasks.
5. Initiation as an aspect of motor control
Motor initiation impairments (specifically) are seen as the main problem in Parkinson's. The main problem is with getting started on movement such as walking and being very slow, but they also sometimes get stuck in repetitive behaviour. Another condition where initiation and maintenance of movement is a dominant feature is catatonia. It is now known that catatonia is quite common in autism - occurring in up to 20% of autistic people. It is also possible that subclinical catatonia is even more common and causes initiation problems that are mainly expressed in a problem with mental task engagement rather than initiating movement. These are the people I'm most interested in.
What I found interesting in my research so far is that there is a common pattern of problems with:
These three areas of impairment (call it 'Buckle's triad of initiation impairments' ;)) are commonly seen to varying degrees in:
Because one of the causes of this triad is quite well understood, i.e. deficiencies or damage to the basal ganglia in Parkinson's, these regions could be important in other conditions that share those characteristics.
One of the biggest problems with the research so far is that similar outcomes are being approached through completely different lenses depending on the most obvious problem the person has. This leads to different terms being used (37 of them!) and different ways of looking at the same problem (i.e. as behavioural, psychiatric, or neurological).
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