A study published May 19 in the scientific journal Nature Human Behavior challenges prevailing theories about our ability to solve complex problems and how certain mental disorders affect this ability.
“Patients with obsessive-compulsive disorder (OCD) are thought to have problems developing complex problem-solving strategies,” said lead researcher Albino Oliveira Maia, director of the Neuropsychiatry Unit at the Champalimaud Foundation in Portugal. “However, our new experimental approach provides strong evidence that goes against this theory.”
The team of this psychiatrist and researcher made the discovery by investigating how healthy individuals and patients with obsessive-compulsive disorder differ in the way they solve problems. “In general, people use a combination of two complementary strategies, known as the model-free approach and the model-based approach,” Oliveira Maya explained. “While healthy individuals use both strategies flexibly, OCD patients tend to use the model-free approach.”
Two problem solving strategies
The modelless strategy is relatively simple and works well in stable environments. For example, imagine the following scenario: You eat breakfast every morning on your way to work. There are two sweet shops along the road: “O Grão” and “Aroma”. When you need to get to work early, you will realize in time that the “Aroma” cafeteria usually receives the indispensable breakfast companions – fresh croissants – before the pastry shop “O Grão”. So, taking the supermodel-free approach, I would always go to the “Aroma” pastry shop first, and only when it didn’t have a croissant, would I try the “O Grão”.
However, this model-free approach will not work well if, for example, the seller of croissants has two drivers taking different routes. Thus, in the weeks when the first driver is on duty, you will receive “O Grão” croissants early. But if it’s the driver’s second week, then the Aroma patisserie will receive the croissants first.
If you can find the ‘model’ – that is, if you know the availability of croissants depends on the driver working in a given week – you will be able to avoid unnecessary trips. Therefore, even if “O Grão” receives the much-requested croissant several weeks early, on the first Monday it does not happen, you will know right away that during that week, the sweet shop “Aroma” will be the safest option .
“Even if a model-based strategy is more computationally demanding, particularly while addressing what is happening, it is, in complex circumstances like the one in this example, more effective in optimizing its actions,” said Oliveira Maya.
Change the rules of the game
According to Oliveira-Maya, scientific studies evaluating these strategies have traditionally applied a puzzle called the “two-step task,” which is similar to the second scenario we presented, which is more complex.
“These studies have shown that healthy individuals use a combination of a simpler model-free strategy and a more complex model-based strategy, when solving these types of tasks. Conversely, OCD patients tend to adopt a less efficient strategy,” explained Oliveira Maya. To the fact that OCD sufferers are strongly tied to habits, and therefore tend to repeat actions even if they do not serve a useful purpose.
While this conclusion appears linear and consistent, there is a problem. Because the tasks used in these studies are often very complex, participants are always given a full explanation of the model before the test begins. However, to date, no one has rigorously tested the effect of these prior instructions – and in particular their absence – on the participants’ problem-solving strategy.
From mice to humans
To find out how people can only do free trials, the Oliveira-Maya team teamed up with Thomas Acham, a neuroscientist now at Oxford University, who recently developed a two-step task for mice.
“Because it is not possible to give verbal instructions to mice, Thomas created a very simple task for animals to be able to decode a model by trial and error. In his research paper, published in the journal Neuron just over a year ago, Thomas showed that mice can indeed solve puzzle. So we decided to adapt this task to humans and test whether healthy individuals would naturally adopt a model-based strategy, as is generally accepted,” explained the study’s first co-author, and then doctoral student, Pedro Castro Rodrigues.
The results of the experiment came as a surprise to the researchers. “Although there is extensive experience performing the task, only a small minority of the group of 200 developed a model-based strategy. This is impressive, given the task’s relative simplicity, which indicates that humans are surprisingly poor at learning causal models. Based solely on experience, commented Castro Rodriguez, a psychiatrist currently at Centro Hospitalar Psiquiátrico de Lisboa.
OCD patients are similar to healthy individuals
At the end of the third session, the researchers divided the subjects into two groups. One group received a full description of how the puzzle worked, while the other group received no explanation. Finally, the researchers held a fourth and final session to assess the impact of receiving instruction on a problem-solving approach.
The difference between the two groups was clear: almost all people in the group that received an ‘interpretation’ – both healthy participants and patients with OCD – adopted a model-based strategy. On the other hand, most participants in the other group, who received no ‘interpretation’, continued the model-free approach.
“These results were fantastic,” said Anna Maya, a doctoral student who took part in the study. “Not only did they reveal that interpretation plays a more important role than previously thought, they also showed that, under certain conditions, patients with OCD are more likely to be able to solve a complex task optimally, than healthy individuals.
What is the reason for the conflict between the results of this study compared to the previous results? According to the authors, there are several possible explanations. The first was that the task was relatively simple, as were the instructions. “Because classic two-step tasks tend to be very complex, the interpretations are also very complex. It is natural to conclude that a seriously ill person and someone in severe distress will have more difficulty processing this type of information, explained Oliveira Maya.
Another premise is that starting with the free trial makes a difference. Is it possible for the three sessions to end without instructions to prepare patients for an explanation? “In this study, we did not directly test this hypothesis, but there is some evidence that this might happen. If future studies support this formula, it could lead to the development of new psychological and behavioral therapies for patients with OCD and possibly even other mental health disorders,” Castro Rodriguez also suggested.
The importance of clear explanations in learning
The team continues to explore this topic by following different paths. “In this project, we also collected image data from individuals performing the task inside an MRI machine. Therefore, the most urgent option would be to search for neural correlates associated with the transition from one strategy to another, after receiving the explanation of the task,” said Castro Rodriguez.
“Pedro’s work is part of a broader project in the lab – the Neurocombe project,” added co-author Bernardo Barahona Corre, a psychiatrist at the Champalimaud Foundation. “This project, which I lead with Albino, will investigate many aspects of OCD, with a particular focus on an area of the brain called the anterior orbitofrontal cortex. We believe that this area is important both for central manifestations of this disorder and for the adoption of model-based action strategies in tasks Like the ones we used in this experiment.”
“Ultimately, these findings highlight the importance of clear explanations in learning,” emphasized Oliveira Maya. “It seems that free exploration may not be the most effective way of acquiring new knowledge. In fact, I have already talked to my children about it,” he added jokingly, “explaining to them that they should pay attention to their teachers.”