If you have faced any of the below situations, predictive coding may have answers to the mysteries :

  • Ever started your day angry and found more angry people to maintain your state ?
  • Ever wondered how creative visualization helps us achieve our outcomes ?
  • Ever wondered how creative people can find possibilities where others looked and quit searching ?
  • Ever realized why sometimes you seem to be able to accurately predict future events with uncanny precision ? Predictive Coding has answers to all of these.

As per Wikipedia, Predictive coding (also known as predictive processing) is a theory of brain function in which the brain is constantly generating and updating a mental model of the environment. The model is used to generate predictions of sensory input that are compared to actual sensory input. This comparison results in prediction errors that are then used to update and revise the mental model.

Predictive coding is a controversial theory that is changing the way neurosciences classically thought of the brain as a feature detector which is sitting idle till it recognizes the presence of an environmental stimulus, processing the signal to identifying and pattern matching it with stored memories (perception), finally sending signals to produce a behavioral response (action).

“Predictive coding is as important to neuroscience as evolution is to biology.” —Lars Muckli, neurophysiologist, University of Glasgow

The predictive coding theory proposes that the brain actively and perpetually makes predictions about the future, matches those predictions with incoming sensory data and takes a series of actions to reduce surprise or prediction shock to the organism. In addition, the theory implicitly suggests that perception is the culmination of final processing that occurs between competing top-down predictions and bottom up sensory feed.

“You experience, in some sense, the world that you expect to experience ~ Andy Clark”

As per the proponents of the predictive coding theory, the human brain perpetually generates variable models of the world and then processes the incoming sensory data.feed to make plausible predictions to reduce surprise and shock. Human brain estimates both probability densities as well as expected precision of its environmental observables. The brain computes a probabilistic, always evolving generative model of the world, and minimizes prediction error relative to the generative model’s expected states.

predictive coding

Although predictive coding does not explain or highlight this, I have been a long term mediator using EEG driven feedback and all meditators know that the top down predictive feed is inhibitive in nature and the bottom up sensory feed is excitation. Too much excitatory feed can damage the nervous system. The excitatory feed has lot of possibilities or Variety (V) and controlled opening of the excitatory feed leads inventors and creative people to find new possibilities in the service of their creativity. Taking it to the extremes, psychedelics experience the vast range of possibilities under the effect of the drugs. On this basis, the inhibitive nature of the top down predictive feed maintains or creates habituation and stability in our lives.

In the 20th century we thought the brain extracted knowledge from sensations. The 21st century witnessed a ‘strange inversion’, in which the brain became an organ of inference, actively constructing explanations for what’s going on ‘out there’, beyond its sensory epithelia. One paper played a key role in this paradigm shift ~ Nature Neuroscience 

I will also discuss in future articles how predictive coding provides a basis for understanding why and how creative visualization works. It is easy to decipher that there is a lot more happening in our brain and mind as a result of creative visualization rather than the “universe conspiring to give you what you want”. As a matter of fact, I will go further and make a claim that creative visualization helps us change our perceptions and actions to achieve what we want. The process is incremental and intuitive and hence, you can only connect the dots in hindsight.

Other propose that predictive coding offers a unified view of perception, cognition, and action in a single system. Perception and Action are opposite sides of the same coin. Using both action and perceptions (see Figure below), the brain can minimizes surprise or prediction shocks (errors) in a variety of the ways. If no error is generated by the brain, then no action requires to be taken and no perception change is required. A variant of the no change model is when the brain suppresses the incoming sensory feed so that the mental model/perception requires no change at all. Note that as perception is an emergent effect of balancing top down predictive feed and bottom up sensory feed, perception change cannot be achieved directly, one has to change the mental model or belief which leads to a change in perception. In other cases, the original perception can remain same but the agent can take action (intuitive) to either fulfill the perceptive command or to search for environments that fit the existing paradigm. In the most novel case, the agent changes it’s perception but also changes the environment using its actions. Inventors and super achievers can change the world by changing their paradigms/mental models.

predictive coding unifying view

It is my premise that our unconscious mind is the engine making predictions for the future based on the the past and holds multiple variations of those predictions in its mind till one plausible prediction is selected and rest are discarded. The discarded predictions are possibilities rich and if one can find a way to tap into them as inventors do, then one can find gold in the haystack of dumped predictions. If we know how to tap into the workings of our unconscious/subconscious mind, we can tap into the system that is perpetually carrying out unconscious search for possibilities to our advantage. As a matter of fact, I created a program named Mental Model Innovation, that I recently shut down to exactly do that.

Predictive Coding potentially has evolutionary benefits and saves the brain free energy. When one walks down the house to get a drink from the refrigerator, they are not seeing a live feed of the items around the house, but, a perceptual model of the items stored in low resolution to save energy. Predictive Coding is also used in video editing as one frame moves to the second frame. The video encoding method only encodes the differences between adjacent frames rather than getting details of every frame. Such a method is energy saving but also uses less space to store data.

Let us now discuss some use case scenarios which will help one to understand the concept of predictive coding better.

You close and lock the front door of the house and go out for a party with friends. When you return, you find the front door close and unlocked. Based on past events (top down mental model), your unconscious mind was predicting that you will find the door closed and locked. As soon as you find the door is unlocked (bottom up feed), the prediction fails creating stress and surprise. Thoughts rush your mind is your brain’s way of dealing with the prediction error .

Is their a burglar inside ?

Did you leave the door unlocked ?

Are you losing your mind and memory ?

You cautiously step inside the house and check everything is in order, but still cannot explain the anomalous door unlocked event. You sit down on the couch, talk to your friend, explain the anomaly and suddenly notice the keys lying on the table opposite your couch. It seems that you never took the key with you, thought you had unlocked the door but actually you forgot to unlock the door. Mystery solved.

However, you failed to notice that your unconscious mind looped in your conscious mind to first get you to relax and sit down and then search for an environmental cue (keys on the table) that would solve the mystery. You took action to sit down and you took action to sit down right in front of the keys. The cognitive dissonance you felt for the moment was due to a conflict between your prediction system and sensory feed and a part that made you forget your keys in the first place. It is easy to see how difficult and stressful it would be experience multiple prediction shocks and surprises every day. Taken for granted by us is how the unconscious mind is working 24 X 7 to reduce surprise for us.

A point to note here is that surprise is not the only outcome of prediction error. Stress, Disappointment, Resentment and Anger are other outcomes. Even humor is a sort of prediction error. Our unconscious mind and brain are always predicting the next sequence of word being spoken or read and when the prediction error fails in a good way, we laugh.

It is now easy to make a point that our emotions play a very important role in understanding how we feel in our existing environment. As we become less observant of how we feel, the prediction errors remain in our system making us accept our current reality.

The most profound part of it is that it shows us how vulnerable our mental function is ~Philip Corlett, Yale School of Medicine

Predictive Coding also explains some mental disorders and how some people experience reality in a delusional way as their top down inhibiting predictive function loses the fight against the bottom up sensory feed opening up their sensory feed.

The theory is promising for technological innovation as well. In 2018, the company “Deep Mind” introduced a new algorithm “Neural scene representation and rendering” which mimics the predictive coding framework. According to the authors “the algorithm changes the parameters of its [predictive] model in such a way that next time, when it encounters the same situation, it will be less surprised“. The predictive coding theory further has the potential to provide insights into the Bayesian brain framework .

Please check back this post in few days as I will update this with more details.