Brain Learning: How Classical and Operant Conditioning Work Together to Shape Behavior

Left to right – PhD student Eyal Rozenfeld & Prof. Moshe Parnas

How do we learn and form memories? A new study from Tel Aviv University offers a surprising answer: our brains engage in a fierce battle between two fundamental learning processes, classical and operant conditioning. The researchers discovered that these systems are mutually exclusive, with only one able to take control at any moment. This explains why trying to learn two opposing reactions to the same trigger can lead to confusion and an inability to respond effectively. This “learning conflict” was demonstrated in fruit flies, which, when trained to associate a smell with both a randomly delivered and a self-inflicted electric shock, became bewildered and failed to exhibit a clear response.

The intriguing research was led by Prof. Moshe Parnas and PhD student Eyal Rozenfeld from the Laboratory for Neural Circuits and Olfactory Perception at Tel Aviv University’s Faculty of Medical and Health Sciences. The findings were published in the prestigious journal Science Advances.

We learn in various ways, from passive associations (classical conditioning, as seen in Pavlov’s dog) to learning based on consequences (operant conditioning). While these systems were once thought to work harmoniously, the potential for conflict raises important questions about how we respond to complex situations. Imagine mice trained to fear a smell using both methods. Classical conditioning would lead to freezing, while operant conditioning would lead to fleeing. But what happens when both memories are active? This study explores this very question: will the mice freeze, flee, or exhibit some other behavior?

Can the brain learn two different lessons at the same time? A fascinating study on fruit flies (Drosophila) from Tel Aviv University suggests not. Researchers discovered that the brain actively prevents simultaneous learning through both classical and operant conditioning, choosing instead to prioritize a single response. In their experiments, flies were trained to associate a smell with an electric shock. This resulted in two distinct learned behaviors: freezing (classical conditioning) or fleeing (operant conditioning). However, when researchers attempted to teach both responses simultaneously, the flies learned nothing at all. The study also successfully identified the brain mechanisms responsible for this surprising limitation.

“Our research completely changes the way we have thought for decades about how our brain learns,” explains Prof. Parnas. “You can think of the brain as engaging in a ‘mental tug-of-war’: if you focus on learning through your actions, the brain blocks the formation of automatic associations. This helps avoid confusion but also means you can’t learn two things simultaneously.”

“Fruit flies have simple brains, which makes them easy to study, but their brains are surprisingly similar to those of mammals—and thus to our own,” added Parnas. “Using powerful genetic tools, the researchers gained a deep understanding of how different learning systems compete for ‘space in the brain.’ They found that the brain’s ‘navigation center’ intervenes to ensure that only one type of memory is active at any given moment, preventing clashes between the two systems. This discovery can help us understand why multitasking sometimes leads to forgetting important details.”

Eyal Rozenfeld concludes: “Not only does this discovery reshape what we know about human learning, but it could also lead to the development of new strategies for treating learning disorders. By better understanding how memories are formed in individuals with conditions like ADHD or Alzheimer’s, we might be able to create new treatments. It’s fascinating that our brain selects between different learning systems to avoid confusion—all without us even being aware of it.”