The monotropism account of autism – which was introduced by Dinah Murray, Mike Lesser, and Wenn Lawson in 2005 – is, within the autistic adult community, probably the dominant theoretical approach towards understanding what autism is.  Many autistic people – myself included – find monotropism to be quite a bit more consistent with our personal experiences than other theories of autism.  I suspect this might have something to do with the fact that the monotropism account was developed by autistic people, and the other theories were developed by neurotypicals…

In any case, the monotropism hypothesis – as originally proposed – suggests that the central feature of autism is hyper-focus, an attention tunnel narrower than one would find in neurotypicals.  This hyper-focus is conceptualized to be endogenous, meaning it is motivated internally “from the top down” by the intense interests of the autistic person.

Unfortunately, the monotropism theory has been almost totally neglected by neurotypical researchers.  In the sixteen years since the theory was proposed, thousands of autism research papers have been published, but I don’t think a single one of them was an experimental research study set up with the goal of testing the monotropism hypothesis!  I believe the monotropism hypothesis certainly deserves more attention than this (and one of the main goals of my thesis research will be to explore monotropism in autism).

However, I’ve also been doing some thinking about the theory of monotropism and I think there are some important modifications that could be made to enhance it.  Most importantly, I think we need to re-evaluate whether autistic hyper-focus is solely endogenous or whether hyper-focus can also be exogenous or “bottom-up”: that is, whether hyper-focused attention can also be susceptible to being externally captured by highly salient or distracting stimuli in one’s environment.

Based on my experiences, accounts from other autistic people, and experimental findings, I do think that autistic hyper-focus can be either endogenous or exogenous.  Expanding the monotropism account to recognize the role of exogenous attention capture in autism helps us explain important aspects of autistic experiences, such as sensory overload.

Exogenous hyper-focus also offers responses to key lines of evidence that would contradict an endogenous-only model of autistic hyper-focus.  Research by Anna Remington and other scientists suggests that autistic people have an enhanced perceptual capacity allowing us to process multiple things at once: a wider focus of attention, rather than a narrower one.  This would be decidedly inconsistent with an endogenous-only form of monotropism.  However, I think the results of these perceptual capacity studies can be accounted for by exogenous attention capture and distraction.

Exogenous hyper-focus also helps us explain the frequent co-occurrence of autism and ADHD.  Many people don’t realize this, because ADHD is supposed to be characterized by a “deficit” of attention, but ADHDers can – just like autistics – experience the sort of endogenous hyper-focus brought about by intense interests and flow states.  However, ADHDers can of course also experience distraction and attention capture, and again I’d argue the same is true in autism.  Intuitively, one might think that endogenous, top-down hyper-focus and exogenous attention capture ought to be opposites, but instead, it seems they are consistently found together, like two sides of the same coin.

Evidence for endogenous hyper-focus

Before we get to the exogenous capture of the narrow/intense attention tunnel, let’s recap some of the reasons for thinking that Murray and colleagues were right to emphasize the importance of endogenous, top-down, internal interest-driven hyper-focus in autistic people.

First, most obviously, we have intense interests: what are our intense interests if not endogenous hyper-focus?  Through our intense interests, we enter into flow states where external distractions are minimized and we focus narrowly on something we find inherently, passionately, and intrinsically motivating.¹  These are highly positive states, and I greatly enjoy my many and varied intense interests.

But Dinah Murray and colleagues didn’t limit themselves to intense interests: they argued this same sort of endogenous hyper-focus could account for all of the “autism symptoms” then included in the DSM diagnostic criteria, and Fergus Murray’s article about this adds some further points.  Monotropism can relatively easily account for autistic stimming.  Routines probably also work well with monotropism.

One of the most noteworthy things about the monotropism account is that it might be able to account for some of the early differences in social attention and novelty preference in the early development of autistic children.  Young autistic kids often seem disengaged from their environment or seem to be exploring highly idiosyncratic stimuli rather than (as most young children do) exploring new things or interacting with nearby adults.  These sorts of early differences in social attention and novelty preference are thought to be highly influential in autistic people’s development, and one of the key insights of a developmental perspective on autism is that this can result in key learning opportunities being missed.²  Hyper-focus can, after all, be a strength or a weakness depending on context.  This might³ account for some of the large discrepancies we observe between older autistic children’s performance on tests more related to crystallized cognitive ability (which might tap into learned information) and those more about fluid cognitive ability (reasoning, not requiring learned information).

One of the age-old questions in autism research is whether autism is primarily a social disability, whether it is domain-general, or whether there are separable/fractionable social and domain-general components.  I tend to think that the non-social aspects of autism (e.g., intense interests, sensory overloads) are much, much too important to be ignored, and the social theories don’t generally do a good job of explaining these non-social aspects.  It’s of course possible that there is one aspect of autism causing early differences in social attention that go on to cause (among other things) broader social and communication differences later on, while a second and independent aspect does the non-social stuff.  However, this requires us to believe that the social and non-social aspects of autism appear together purely by chance, which never struck me as terribly plausible or parsimonious.

It’s quite possible, given the heterogeneity of autism, that there are multiple routes to it and that some don’t go via monotropism, but to me it is highly parsimonious to believe that, in many autistic children, monotropism and endogenous hyper-focus could affect social attention early on.  Quite simply, social stimuli that neurotypical kids generally find engaging might fall outside the autistic person’s interests and thus outside the attention tunnel in autism.

Interestingly, some recent eye-tracking studies, like this one by Avni and colleagues or this by Tenenbaum et al., show that the dominant pattern in autistic children’s attention to social videos is gaze idiosyncrasy, with different autistic children ending up looking at different things.  This is in contrast to typically-developing children, who end up looking at more similar things to each other.  Reduced social attention could just be one way this monotropic idiosyncrasy of attention and interests manifests.

Other aspects of autism that are highly consistent with monotropism are the arguably somewhat similar concepts of sticky attention and autistic inertia.  Sticky attention is an idea that originates from neurotypical researchers.  In a seminal study in Canada, Reginald Landry and Susan Bryson found that autistic children were very slow to disengage their attention from one stimulus when a new stimulus was presented to the side.  These results have subsequently been supported by numerous other similar studies.  Meanwhile, autistic adults were developing a related idea more grounded in daily life than in lab-based tasks: that of autistic inertia.  Many of us find it difficult to transition from one thing to the next, to initiate a new task or to stop an ongoing task.  Autistic inertia hasn’t been well-researched, but fortunately Karen Buckle recently completed a preprint of a qualitative study examining inertia.⁴  Both sticky attention and autistic inertia are highly consistent with monotropism.

Autistic inertia might also help to explain cases where young autistic kids seem disengaged from their environment, as opposed to intensely focused on idiosyncratic aspects of their environment.

Evidence for exogenous hyper-focus

However, let’s pause for a second: are findings like elevated sticky attention only consistent with the endogenous variety of hyper-focus?  The stimuli being presented in these “sticky attention” studies aren’t specifically chosen to be interesting to participants, so doesn’t the fact that these stimuli capture attention long enough to slow the transition to looking at the next stimulus indicate some level of susceptibility to attention capture?

Especially when we are outside of flow states,⁵ I do think autistic people’s hyper-focussed attention can be captured exogenously by stimuli in our environments.

Indeed, although this hasn’t been strongly emphasized in the monotropism account, exogenous hyper-focus is not ignored by Murray and colleagues (2005), who comment that “if the current leading interest is not strongly enough engaged, there may be instability in which tiny stimuli keep drawing the attention.”

I certainly think many of the sensory aspects of the autistic phenotype can reflect exogenous hyper-focus.  Admittedly, autistic sensory interests probably reflect endogenous hyper-focus.  However, what about sensory overload?  Fergus Murray (2018) comments that sensory distress can reflect our attention being “pulled away from where we want it to be,” such that our attention has conflicting intense focuses on the person’s own interest as well as the intrusive sensory stimulus.  I don’t disagree with this, but I would add that sometimes the overload can reflect exogenous hyper-focus alone, with no endogenous component: that we hyper-focus on an overly intense stimulus, or find our hyper-focus exogenously pulled back and forth between multiple overwhelming stimuli.  In the narrow/intense hyper-focused attention tunnel, these stimuli could be far more distressing than they would be to a neurotypical person.

Other sensory experiences can also be relevant here.  Autistic people can often experience sensory distractions, where seemingly minor background stimuli end up pulling our attention away in problematic ways.  For example, one might be trying to write an exam and one ends up hopelessly distracted by the flickering lights.  These distractions can often turn into aggravations/frustrations (what we call misophonia in the auditory domain) when the stimulus is an unpleasant or annoying one.

This probably exacerbates and is exacerbated by anxiety, which has been associated with sensory hyper-sensitivity in autism in much prior research.  When researchers try to understand anxiety, they often do so in terms of vigilance: because one is worried about threats, one vigilantly scans one’s environment for potential threats.  When a person with anxiety caused by sensory overloads sees an aversive sensory stimulus, they might then focus on this stimulus, worsening the overload.  If they have a monotropic attentional style, their focus on the stimulus might be narrower and the experience more intense and distressing, worsening the anxiety.⁶

A final important sensory domain may be multisensory integration: some autistic people can struggle to integrate sensory stimuli in multiple modalities like vision and hearing. This might reflect a narrow attention tunnel hyper-focussing on particular stimuli or aspects of stimuli.

There are other findings that suggest attention is commonly driven exogenously, from the bottom up by salient stimuli, in autism.  For example, Courtney Venker and colleagues recently published a paper showing that young autistic children are more likely to focus on highly salient stimuli.

Perceptual capacity and monotropism

I also mentioned earlier that I thought a version of the monotropism theory incorporating exogenous, bottom-up attention capture helps us deal well with an empirical literature that at first glance seems to contradict or rebut monotropism: the increased perceptual capacity literature, in which work by Anna Remington is especially prominent.

Essentially, these researchers have repeatedly, in a number of different studies, found that autistic people are less likely to ignore and more likely to notice stimuli that are irrelevant to the tasks being used by the researchers.  For example, in a particularly amusing study, Remington and Fairnie (2017) asked participants to listen to a recording of four people preparing for a party.  They were told to pay particular attention to a conversation between two women so they could answer questions later.  Partway through the recording, a fifth voice started declaiming, “I’m a gorilla,” which was repeated numerous times for a total of about 20 seconds.  When later asked if they heard anything unusual, only 12% of the neurotypical participants had noticed the gorilla voice, whereas about half of the autistic participants noticed.  The neurotypicals successfully filtered out everything except the conversation, whereas many of the autistic people were also noticing the gorilla.  This seems to suggest a wider focus of attention – an increased perceptual capacity – in autism, not a narrow attention tunnel!

That’s until we consider exogenous attention capture.  It seems likely that the autistic participants weren’t strongly endogenously internally motivated to attend to the tasks set up by the researchers, so they probably wouldn’t have entered flow states.  This would make them highly vulnerable to having their attention exogenously captured by distracting stimuli in their environments.

Indeed, after I started thinking about monotropism and exogenous attention capture in autism, I was fascinated to hear that Steve Luck and other researchers at UC Davis – literally just across the parking lot from where I work⁷ – had done research on hyper-focus in schizophrenia.⁸  In some of their studies, the hyper-focus in question seems to be driven not by participants’ interests but by stimuli that capture attention.  For example, in a 2017 paper, Risa Sawaki and colleagues asked participants to focus on a central location and look for stimuli of a particular target colour, but the participants with schizophrenia seemed to be hyper-focusing on distracting stimuli of the same colour when they appeared at peripheral locations the participants weren’t supposed to be looking at.  If hyper-focus can be captured in schizophrenia, why not autism?

Monotropism and hyper-focus as transdiagnostic phenomena

Considering the evidence for hyper-focus in schizophrenia also helps us see that hyper-focus and monotropism aren’t just found in autism: as Brandon Ashinoff argues, we can see evidence for endogenous, top-down hyper-focus associated with multiple diagnoses.  Similarly, it seems like we can see bottom-up capture of the attention tunnel by stimuli across different diagnoses.

ADHD is a particularly interesting case.  ADHD is, according to the almighty and infallible (note sarcasm) DSM, characterized by “a persistent pattern of inattention”.  That’s not untrue as such – exogenous attention capture and distractibility are clearly quite characteristic of the inattentive subtype of ADHD – but it’s definitely not the whole story.  Indeed, we actually know from papers like this one that ADHD is also associated with endogenous hyper-focus and flow states.

This is particularly fascinating in light of the fact that ADHD and autism frequently occur together.  If we believed that ADHD was all about inattention and distraction, a monotropism theory that conceptualized autism as being all about hyper-focused intense interests might have trouble explaining that overlap.  However, if we instead understand autism and ADHD as each being characterized by a mixture of endogenous, top-down and exogenous, bottom-up hyper-focus, the overlap would seem much more natural.

Indeed, I think Murray et al. (2005) were always clear that they were speaking of a distribution of attentional strategies varying across the whole population, with autism just being an extreme end of that continuum. I completely agree we should think about these things dimensionally. It might just be the case that autism isn’t the only diagnosis at the extreme ends of dimensions of attention.

What, then, distinguishes autism from ADHD?

In general, although I hope I’ve shown here that endogenous and exogenous hyper-focus can coexist with and are probably intertwined with one another in both autism and ADHD, this doesn’t necessarily mean they are in equal balance.  In ADHD I suspect we might tend to see somewhat reduced endogenous hyper-focus and somewhat more exogenous attention capture than in autism.⁹  I also think it might be reasonable to think that the autistic tunnel might generally be narrower than attention in ADHD, or at least more intense/hyper-excited, which might explain why sensory overloads perhaps seem to be worse in autism than ADHD.  Finally, I believe we should also think about the executive functions that are involved in ADHD and autism and how those are similar and different.

Summary and Conclusions

To recap, I’ve tried to show in the post why I think the monotropism framework has a huge potential to account well for autistic behaviour and experience that is, unfortunately, still being ignored by most neurotypical researchers.  Not only is the monotropism account highly consistent with the experiences of many autistic adults, but it also does a good job of accounting for a lot of the behaviours we see in young autistic children.  It has relevance to both the social and non-social domains of autism.  It also has many important real-world implications, especially the need to respect and harness autistic people’s own interests.  It might be necessary to sometimes shape or redirect problematic interests, but neurotypical preferences and requirements should not be imposed on autistic people.

I have also argued that the monotropism theory’s focus on endogenous, top-down hyper-focus could be usefully complemented through increased recognition of exogenous, bottom-up capture of hyper-focused autistic attention.  I don’t think we should think of these as opposing phenotypes, but as two sides of the same coin.  Whether we look in autism or beyond it, endogenous hyper-focus and exogenous attention capture often seem to run together.

I’m curious to hear what people reading this post think of the changes to the monotropism theory I’m proposing here!  Please don’t hesitate to add comments below about that, or of course about anything else about this post.

Also, just repeating a disclaimer: autism (as well as similar disabilities like ADHD) are obviously extremely complicated.  They’re heterogeneous and they can be caused by various different factors.  There are likely many different neurobiological routes towards monotropism, which I won’t discuss in this blog post because I’ve already covered a lot of ground.¹⁰  It’s also not clear that monotropism is the only way that one could end up with a phenotype characterized by autistic behaviours.  Thus, while I do genuinely think that monotropism is the best general framework for understanding autism that we have, and while I hope it can be helpful transdiagnostically as well, I’m certainly not trying to claim that it is the only or definitive explanation!  For example, while I tend to focus on non-social explanations for the reasons I mentioned above, it might be premature to rule out the possibility that in some autistic people factors like early differences in social attention are directly affected in autism, rather than just indirectly affected via an ultimately non-social factor like monotropism.

1. I’m technically hyper-focusing right now, because autism is an intense interest of mine. It’s all very metacognitive…
2. The best approaches to early intervention for young autistic kids respond to this issue by having adults use children’s natural interests to engage the young autistic children.  This allows autistic children to access naturalistic and internally-motivating opportunities for social interaction and learning, and it doesn’t put any pressure on the child to comply with interventionist demands.  It is also not an attempt to change who the child is or force them to conform with neurotypical expectations.  It’s just an attempt to help ensure autistic children have their best chance to reach their potential as autistic people. See more here.
3. Along with other factors such as timing and perhaps even hesitancy/anxiety around responses, along with in some cases the a lack of motivation to comply with bizarre and uninteresting requests from those administering the tests.
4. This is, incidentally, a perfect of why I think we need autistic autism researchers: besides our personal insights, we can also draw on the collective knowledge of our community, which is an invaluable resource often neglected in traditional autism research.
5. Incidentally, I’ve learned it’s easier to cope with overwhelming sensory environments – e.g., before the pandemic, when waiting in a noisy room for a seminar or talk to begin – if I distract myself with an engaging task on my computer: if I deliberately get myself into a flow state. This minimizes my susceptibility to having my attention captured by overwhelming and distressing sensory stimuli. Downside: it’s hard to re-orient attention later, e.g., when the speaker giving a talk begins, which kind of defeats the purpose of going to talks. Obviously, a better solution would be making the sensory environment more accessible!
6. Indeed, I also wonder about the role of monotropism in mental health generally and rumination in autism. Rumination isn’t an environmental stimulus, so this isn’t stimulus-driven exogenous attention capture, but we’d generally prefer it if our attention wasn’t captured by these thoughts. Of course, I’m not ignoring the reality many of our mental health challenges are probably driven by us being a marginalized group of people who are more likely to have unpleasant experiences than neurotypicals. Whatever the role of monotropism in rumination, I think context and life experience are also vital to understanding autistic mental health.
7. Admittedly, I mostly work at home currently due to the COVID-19 pandemic, but when I do go into the lab, it’s across the parking lot from their lab.
8. Which, it should be noted, is similar enough to autism in some ways that researchers were arguing relatively recently in the grand scheme of things over whether schizophrenia and autism are the same thing or not, as well as struggling to distinguish them in practice.  This paper from 1971 has more to say about that issue.
9. Where autism and ADHD occur together, this might mean the individual has a more equal balance of both endogenous and exogenous forms of hyper-focus.
10. Another thought to save for the future: when is hyper-focus narrow, intense, or some combination thereof?