In this article I’m going to introduce a hypothesis relating to how the brain processes facts and sensory information that I use to increase understanding of neurotypical (NT) and neurodivergent (ND) communication: top-down vs bottom-up processing.
Then I’ll describe the benefits and challenges of being a bottom-up processor, often apparent in ND people, including how can impact communication at work.
I’ve added references to the end of the article so you can read more.
Top-down processing
In the late 60s and early 70s, psychologists began to formalise ideas about how the brain processes information.
Richard Gregory introduced the phrase “top-down processing” to describe how our brains absorb ‘just enough’ of what’s going on around us, then use prior knowledge and context to fill in the gaps.
Most people don’t look at every letter of every word they read. They use signals like context, word length and first/last letters to make rapid guesses about what each word and phrase might be. This trick expands outwards from specific words to whole sentences and conversations in which we naturally infer meaning instead of filling in every detail.
If humans simultaneously processed every possible stimulus in the environment, we wouldn’t be able to function - in fact, some researchers believe this is exactly what is going on in autistic people who need constant support.
Inference allows us to meet our needs by ‘turning down’ less important stimuli such as the conversation at the next table or the brightness of the light, and stitching together the important bits into something that makes sense.
Bottom-up processing
Bottom-up processing starts with individual facts and sensory information and builds them up to a broader conclusion.
Many neurodivergent people tend towards bottom-up processing, making fewer inferences and absorbing more sensory information from the environment.
Instead of relying on assumptions, stereotypes, or big-picture context, bottom-up processors examine every piece of evidence to see how it connects to the others before building the bigger picture.
This means their ideas are anchored in concrete facts rather than assumptions. Bottom-up thinkers tend to be honest, accurate and unhindered by received wisdom.
Neurodiversity and Processing styles
As a neurodivergent person (autism and ADHD), I always described my learning style as not seeing the picture on the jigsaw until every piece is in place.
At school I was a slow learners. I’d have lots of questions and gaps I needed to fill before I could even start to understand. Then suddenly, the whole concept would become completely clear.
Weeks later when we returned to the concept, I would find it was still all there when most other people had forgotten it. Because I had to learn every piece of evidence about the concept, it stayed locked into my brain.
When I learned about top-down and bottom-up processing I realised I skew towards bottom-up.
Bottom up Processing, Neurodiversity & Work
20 years ago, Uta Frith coined the term Weak Central Coherence to describe a cognitive bias towards detail-focused thinking in autistic people.
Later, Elizabeth Pellicano & David Burr published papers on brain connectivity that show evidence that autistic brains are more likely than neurotypical brains to process information from the bottom-up. They developed the Bayesian Explanation of Autistic Perception which hypothesises that autistic people have impairments in top-down thinking, inferring and predicting, which leads to varying support needs.
Many neurodivergent people have some degree of bottom-up skew and this impacts how we interact with the world around us.
Enjoying the benefits
Despite the many difficulties inherent in being neurodivergent, the benefits - to employers and to us - are clear.
The ability to dive deeply into a subject, learn everything about it and build new conclusions is invigorating and exciting. We see a lot of things other people miss.
When we have clarity around roles, goals and performance, and we’re free to determine HOW we do the job, we often excel.
But the communication differences between ND and NT people can make these benefits impossible. Here’s an introduction to getting around them…
Dismantling the challenges
Sensory sensitivity
Bottom-up brains rely less on inference and what is already known, which means they are more open to sensory information. Light feels brighter and sounds feel louder because the brain is processing this information alongside everything else.
Design workplaces that reduce the sensory load and provide quiet, dimly lit refuge spaces.
Asking a lot of questions
When you don’t understand a concept until you understand everything about it, information is vital. Not-quite-enough information can make the job impossible. Your autistic employees aren’t challenging you, they just need more answers.
Keep answering questions and provide regular opportunities to ask more.
Over-explaining
When you don’t infer, you assume other people don’t infer either, and so you communicate every detail without leaving anything out.
The best thing to do is listen, or, if pushed for time, interrupt and repeat back to the person what you think they mean.
Rigidity
When something changes, bottom-up processors go back to square 1. It’s like someone took one piece of the jigsaw away and they can no longer see the picture.
A huge part of being able to carry out a task is knowing WHY we are doing it. A change of plan is unsettling because it could reflect a change in that WHY, and this could impact other tasks.
When communicating a change, start with the WHY and be transparent about what it does and doesn’t impact. Answer questions until the questions run dry.
Following instructions ‘too literally’
When you are less reliant on inference you have to believe the words people say, which aren’t always exactly the words people mean.
Check understanding and share instructions in writing as well as verbally.
‘Not listening’
Listening to someone talking through the noise of the world isn’t always easy. Admitting you didn’t hear can be rather humiliating too.
Repeat important instructions in writing.
‘Lacking social skills’
Personally, I believe social skills are relative. ND people lack NT social skills. I also believe that when you spend a long time during early childhood picking your way through an overwhelming amount of sensory information, using your voice to help others feel happy is way down the list of priorities.
Assume positive intent.
‘Missing social cues’
Related to the last one, when you’re taking in so much of the world around you, it’s more difficult to notice when the person in front of you wants to leave the conversation. It’s also difficult to infer meaning when your inference circuits are not as well developed.
Again, assume positive intent.
The need for routines and sameness
If your brain doesn’t always reliably predict what will happen next, the world feels chaotic. Strict routines can be a substitute for missing internal predictions.
Burnout
Bottom-up processing can make many of the everyday things NT people take for granted far more taxing. Yes, many neurodivergent people work and communicate very effectively, but we have to work harder to do so.
Reduce the cognitive load by building clarity and predictability into your workplace, as well as sensory refuges.
Conclusion
Information processing styles don’t reflect everything about every ND person’s experience, but they go a long way to demystifying the differences that lead to miscommunication and conflict in neurodiverse workplaces.
Bottom-up processing is often associated with autism, and not with ADHD, dyslexia, Tourettes and other forms of neurodiversity.
However, as we find out more and more about neurodiversity, we’re starting to see more and more overlap, particularly with ADHD and autism.
This information is shared not to diagnose but to facilitate communication between NT and ND people in the workplace.
References:
https://www.amazon.co.uk/Eye-Brain-Psychology-Richard-Gregory/dp/0198524129 - Eye and Brain: The Psychology of Seeing, Richard L. Gregory
https://thedecisionlab.com/reference-guide/psychology/top-down-processing - an introduction to Top-Down Processing, Celine Huang
https://pubmed.ncbi.nlm.nih.gov/16450045/ - The weak coherence account: detail-focused cognitive style in autism spectrum disorders, Uta Frith and Francesca Happé
https://pmc.ncbi.nlm.nih.gov/articles/PMC9412751/ - Bottom-up vs. top-down connectivity imbalance in individuals with high-autistic traits: An electroencephalographic study
http://wexler.free.fr/library/files/pellicano%20(2012)%20when%20the%20world%20becomes%20too%20real.%20a%20bayesian%20explanation%20of%20autistic%20perception.pdf - When the world becomes ‘too real’: a Bayesian explanation of autistic perception, Elizabeth Pellicano and David Burr
https://www.sciencedirect.com/science/article/abs/pii/S0149763422005115 - 10 years of Bayesian theories of autism: A comprehensive review
https://pubmed.ncbi.nlm.nih.gov/38387375/ - Unpacking the overlap between Autism and ADHD in adults
