The role of variability: From playing tennis to learning language

Variability is crucial for learning new skills. Consider learning how to serve in tennis. Should you always practice serving from the exact same place on the course and aiming for the exact same place? Although training under more varied conditions will be slower at first, it is likely to make you a better tennis player in the end. This is because variation leads to better generalization of what is learned.

Chihuahua and Grand Danois

This principle exists in many areas, including speech perception, grammar and learning of words and categories. For example, infants will struggle to learn the “dog” category if they are only exposed to Chihuahuas, instead of many different kinds of dogs (Chihuahuas, Poodles, and Grand Danes).

“There are over ten different names for this basic principle!”, Says MPI’s Limor Raviv, senior investigator for the study. “Learning from less varied inputs is often quick, but can fail to generalize to new stimuli. But these important insights have not been united in a single theoretical framework, which has obscured the bigger picture.”

To identify key patterns and understand the underlying principles of variability effects, Raviv and her colleagues reviewed over 150 studies on variability and generalization across fields, including computer science, linguistics, categorization, motor learning, visual perception, and formal education.

Mr. Miyagi

The researchers discovered that the term variability across studies can refer to at least four different ones kind of variation, such as specify size (eg number of different examples or places on the tennis court) and scheduling (eg training schedules with different orders or time delays). “These four types of variation have never been directly compared – which means we currently do not know which one is most effective for learning,” says Raviv.

The effect of variability depends on whether it is relevant to the task or not (probably the color of the tennis court is not relevant for serving exercises). But according to ‘Mr. The Miyagi principle (inspired by the classic film Karate Kid from 1984), to train seemingly unrelated skills (like waxing cars) can actually benefit the learning of other skills (like martial arts).

Competitive theories

But Why does variability affect learning and generalization? One theory is that more varied inputs can shed light on which aspects of a task are relevant and which are not (color is useful for distinguishing between lemons and limes, but not for distinguishing between cars and trucks).

Another theory is that greater variability leads to broader generalizations. This is because variation will represent the real world better, including atypical examples (like Chihuahuas).

A third reason has to do with how the memory works: when the training varies, the students are forced to actively reconstruct their memories.

Face recognition

“Understanding the effects of variation is important for literally every aspect of our daily lives. In addition to affecting how we learn languages, motor skills and categories, it even has an impact on our social lives,” explains Raviv. “For example, face recognition is affected by whether people grew up in a small community (less than 1,000 people) or in a larger community (over 30,000 people). Exposure to fewer faces during childhood is associated with reduced facial memory.”

“We hope that this work will arouse people’s curiosity and generate more work on the subject,” concludes Raviv. “Our article raises many open questions. For example: Is the relationship between variability and learning largely the same between species, or are there species-specific adaptations? Can we find similar effects of variability outside the brain, for example in the immune system?”

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