Key takeaways
Scientists long assumed that learning speed depends primarily on our experience — how many times we try and succeed — not the size of the reward. We become better at poker because we keep playing and winning, regardless of the purse being $100 or $100 million.
But new research suggests that the size of the jackpot matters more than previously thought.
Scientists in the Dudman Lab at HHMI’s Janelia Research Campus show that bigger rewards can enable learning to happen faster.
The new findings upend decades-long assumptions that learning depends on experience and the role dopamine plays in the process.
How Reward Size Affects Learning Speed
Like every other neuroscience lab, the Dudman Lab had always assumed that animals learn slowly, and they need hundreds of repetitions, each with a small reward, to learn even simple tasks. Neuroscientists had never thought to examine whether the size of the reward might affect learning.
“The whole field has been doing it for decades and I mean this quite literally, no one ever checked,” says Janelia Senior Group Leader Josh Dudman.
When the team decided to check this assumption, the results were striking. Thirsty mice that were given a few large drinks of water as the reward for completing a task learned much faster than mice rewarded with many small sips — the difference between giving a human a cookie and a single M&M. Instead of taking many days to learn the task using thousands of little rewards, the animals learned the task in one day after receiving fewer than 10 large rewards.
Surprisingly, even though the animals had less experience with the task, the variability between animals also declined dramatically. Normally, one mouse might become an expert in a week while another took a month to learn the same task. With the bigger reward, all the animals were learning the task in a few days.
“As neuroscientists, we resign ourselves to knowing that we’re going to have to train this animal for a few weeks and eventually, they’re going to start to look like they know what’s up,” Luke Coddington, a senior scientist in the Dudman Lab who led the new study, says. “But instead, now in a day, I’m watching these mice just nail it.”
How Dopamine Controls Learning Speed
The researchers found that large rewards increased three components that contribute to how fast animals learn:
Compared to smaller rewards, bigger rewards produced larger increases in dopamine — a chemical messenger in the brain that helps regulate learning and motivation. Importantly, the team also found that the dopamine signals associated with the bigger rewards lasted longer. When they artificially extended the dopamine signals associated with small rewards, they found learning also happened faster.
The team found that the longer dopamine signal led the animals to learn more during each trial and stay more engaged in the task, which led to faster learning.
The level of engagement in the task was also the largest determinant of individual variations in learning.
“We think that when we make dopamine responses way bigger in these experiments, we’re turning all the ‘kids’ in our ‘classroom’ into really engaged students,” Coddington says.
Implications for Neuroscience Research
The new work could change how neuroscientists study skill-based learning. Using large rewards cuts training time and variability, making the learning process easier to study.
The Dudman Lab is already using large rewards in their work. “It changed how more or less all of our current projects are done now,” Dudman says.
It also shows that mice could potentially be trained in more complex tasks than previously thought, empowering researchers to study questions about learning and cognition that were previously out of reach.
“In addition to the practical side, which is very real, we may also end up studying new aspects of cognition we didn’t realize we could study in a mouse,” Coddington says. “If we can properly engage them in the task, then who knows what they can learn.”
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Science
Reward magnitude determines reinforcement learning efficiency
21-May-2026
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