The Sudoku Brain — A Guess Or A Calculated Move?

Have you ever played Sudoku: level hard where you barely see any numbers on the grid and have to make the first move? How does your brain take the first guess? Is your brain making a calculated move or is this simply by trial and error? Does your brain force/trick itself to take an “educated” guess and not commit any errors, or does it only think about achieving the end goal of solving the entire sudoku within the time frame irrespective of the number of errors committed?

Let’s take a different example — In an ice cream store where you have 50 options, how does your brain narrow down to that one top pick? Or, what makes you indecisive up until the point where you finally narrow down on one flavour? Of course, here you know what your options are, you know you have to choose one out of the fifty and you will either like or dislike it. Tons of factors play a role in the choice — colour, toppings, texture, price of a scoop, popularity, etc. However, in Sudoku, you know you have 9 numbers, you know your limitations within 9 boxes vertically, horizontally & within the first 3x3 square. But why does your brain struggle to take a random guess or use logic?

To understand this slightly better, let’s break it down to one question— How does the brain, a highly complex human body part, make a decision or even absorb information? Well, to answer this we need to understand two parts of the brain — You have the Hippocampus and the Prefrontal Cortex which are the petrol and the engine of the brain.

1. Event A— Something visually/physically stimulates and excites the hippocampus neurons. Example — “When I see a dog dancing, it visually triggers a WOW factor in me — like a sensation (primary stimulus)” [Information 1]
2. Event B — Here, another sensation (secondary neurons) are sent to the hippocampus, once again triggering 2 sets of stimulation to the neurons. Example — “Wow! The Dog is still dancing and it just winked at me. This stimulates me even more (secondary stimulus) ” [Information 2]
3. Event C = (A + B) — In this stage, the first sensation (event A) is sent to the prefrontal cortex and this part further looks for supplementary information (secondary sensation) to process the entire event. Example — “Hey Margot, I saw a dog dancing and on top of that it winked at me. Can you believe it? (clubbing 2 and 2 together)” [Structuring data]
4. Event D— Brain processes the entire information and decides the control feedback/action forward. Example — “I just saw a dog that danced and winked at me. And I need to pet it right away” [Decision Making]

Now, in Sudoku, the Prefrontal Cortex is heavily active since the hippocampus receives information continuously on grids and also has to learn and remember the moves. In other words, The PFC churns more when the numbers on the grid are minimum and relatively less when majority of the grids are pre-filled. However, it continuously factors events and information received by the hippocampus. Sudoku, to a large extent, is a game based on heuristics — a problem solving method or a skill that’s based on experience and available information. This means trial and error, and logic.

When the prefrontal cortex receives the information on the grid, it evaluates options of the next move and possibilities of an error. More the information it receives, more the experience, and quicker the brain’s response to make the correct move. But what if there are barely any numbers in the sudoku puzzle?

So, if you’re unsure of your first move, but you know the 9 numbers, and you also know all potential possibilities of a number being chosen for a specific grid, is your move going to be based on logic or chance? We’re not here for the math behind the solution, rather the idea is to understand what tells the brain to choose a number during uncertainty. It is said — “Uncertainty always increases the cognitive load” — Ness labs. This means we use our memory to our fullest extent to make decisions. But to develop the memory you need initial/minimum data. But to get the initial data, the brain needs prior data … and this repeats. So, does the brain need to know anything prior before making a guess or move by logic? Fortunately researchers have studied and have provided a fun fact— a sudoku must have a minimum of 17 clues for 1 unique solution.

That’s great! So, apart from the 2–3 numbers on the grid already provided, our brain pushes itself to place the first random 17 numbers in the grid, post which it registers event A,B,C,D, etc. This is the stage of cognitive overload. Once the events are registered, the Hippocampus processes this stimulation and directs it to the PFC that structures and provides feedback on the controlling feedback/action required. This is the stage where it requires logic — heuristics.

However, the question remains — If 17 clues are required to produce 1 unique result, are the initial guesses made by a human being based on chance or logic? Studies continue …