10 MINUTES, 30 MINUTES, ONE HOUR: IS THERE REALLY AN IDEAL TRAINING DURATION?
It is a question that comes up regularly when designing a training program: how long should a learning module actually be?
Should we favor very short sessions to maintain attention? Is a 45-minute training session long enough to explore a topic in sufficient depth? At what point does a module become too long?
It is tempting to look for a single number but from a cognitive science perspective, the question may be more complex than it seems.
There is no universal duration after which the brain suddenly stops learning. The quality of learning depends much more on what learners are asked to do during that time, the complexity of the information presented, their prior knowledge, and the way the learning experience is structured.
A 15-minute training session can be cognitively exhausting. Another lasting 45 minutes can keep learners engaged until the very end.
Duration matters, but it only tells part of the story.
THE MYTH OF THE ATTENTION SPAN
The rise of microlearning has widely popularized the idea that our attention spans have become extremely short.
We regularly come across claims suggesting that people can only remain focused for a few minutes before their attention begins to decline.
The scientific reality is more nuanced.
Attention does not operate like an identical timer for everyone. It varies according to the difficulty of the task, our interest in it, our level of expertise, our environment, and, above all, the degree of cognitive activity required.
We can passively watch a presentation for ten minutes and quickly lose track of what is being said. Conversely, we can remain focused for much longer when we are solving a problem, answering a question, or making a decision.
The right question is therefore not simply:
“How long can a learner stay focused?”
But rather:
“What are we asking the learner to do during that time?”
THE REAL ENEMY: COGNITIVE OVERLOAD
John Sweller's work on Cognitive Load Theory provides a particularly useful perspective on this question.
Our working memory has limited capacity. When a training session presents too much new information at once, learners must devote a significant proportion of their cognitive resources simply to processing what they are receiving.
As this load increases, understanding, organizing, and remembering new information becomes more difficult.
This is why shortening a training session can sometimes be useful.
But shorter does not automatically mean more effective.
Compressing 40 minutes of explanation into a 10-minute module can even have the opposite effect: more information, less time to process it, and ultimately less learning.
The challenge is therefore not simply to make training systematically shorter, but to better manage the cognitive effort required from learners.
MICROLEARNING IS NOT A UNIVERSAL SOLUTION
Short learning formats offer many advantages. They are easier to integrate into busy schedules, can target a specific skill, and make it easier to regularly reactivate certain knowledge but not every skill can be developed in five minutes.
Understanding a simple procedure does not require the same cognitive investment as learning how to conduct a negotiation, analyze a financial situation, or manage a complex conversation with a team member.
Some skills require time to experiment, make mistakes, receive feedback, and try again.
The constant pursuit of shorter formats can therefore create confusion between two very different objectives: optimizing content consumption and optimizing learning.
The best learning module is not necessarily the one learners complete the fastest.
It is the one that gives them enough time to genuinely learn what it is designed to teach.
WHAT MATTERS IS WHAT LEARNERS DO DURING THE TRAINING
Imagine two 30-minute training sessions.
In the first, learners watch a succession of videos and slides before answering a few questions at the end.
In the second, they alternate between short explanations, questions, realistic scenarios, decisions, and feedback.
The duration is exactly the same.
The learning experience is not.
Research on active learning highlights the benefits of regularly asking learners to retrieve information, explain concepts, or apply what they have learned rather than simply exposing them to content.
Duration then becomes less important than the learning rhythm itself.
A training session can be relatively long without becoming monotonous when it alternates between different types of cognitive effort.
EFFECTIVE LEARNING MAY NOT NEED TO HAPPEN ALL AT ONCE
There is another way to think about training duration.
Rather than asking whether a training session should last 20 or 60 minutes, we can ask whether it makes sense to concentrate the entire learning experience into a single session.
Research on the spacing effect has long demonstrated the benefits of distributing learning over time.
Returning to knowledge after a certain period requires the brain to retrieve it, helping to strengthen and consolidate learning.
An hour of training therefore does not necessarily need to be one continuous hour.
Depending on the learning objective, several sessions distributed over time and combining discovery, practice, feedback, and knowledge retrieval may be more effective than one long block of content consumed all at once.
The objective is no longer simply to optimize the duration of a module.
It is to organize progression over time.
THE RIGHT DURATION IS NOT NECESSARILY THE SAME FOR EVERYONE
There is one final issue with the concept of an “ideal duration”: it assumes that every learner needs the same amount of time.
An employee who already has a strong understanding of a subject probably does not need to go through the same explanations as a complete beginner.
Conversely, a learner experiencing difficulty with a specific concept may need additional practice or a different explanation before moving forward.
Yet strictly linear learning journeys often impose exactly the same duration on everyone.
This is where adaptive learning approaches become particularly relevant.
Instead of deciding in advance that a module must last exactly 30 minutes, the learning experience can adapt according to each learner's responses, difficulties, and level of mastery.
WITH COMPLEMENT, THE QUESTION BECOMES: HOW MUCH TIME DOES THIS LEARNER NEED?
This principle plays an important role in the approach developed by Complement.
Rather than treating learners as passive viewers of content with a predetermined duration, the experience is built around interactions with an AI tutor, questions, realistic scenarios, and feedback adapted to individual progress.
The time spent training therefore serves a genuine learning purpose.
A learner who quickly masters a concept can progress without being forced through unnecessary explanations. When a difficulty emerges, the experience can instead devote more time to interaction, reformulation, or practice.
The objective is not to systematically create the shortest training sessions possible.
It is to make the best possible use of each learner's time.
SO, HOW LONG SHOULD A TRAINING SESSION ACTUALLY BE?
It would be tempting to give a single answer: 15 minutes, 30 minutes, or 45 minutes.
But such a number would ultimately have little meaning without considering the skill being developed, the learner's existing knowledge, and the nature of the learning experience itself.
The ideal duration is first and foremost one that gives learners enough time to understand, practice, and receive feedback without creating unnecessary cognitive overload. Some concepts can be addressed quickly, while others require more experimentation, reflection, or several sessions distributed over time.
In practice, at Complement, we generally recommend sessions lasting between 30 minutes and one hour. We believe this range offers a strong balance: it provides enough time to explore a subject in sufficient depth and create a genuine learning dynamic while remaining compatible with learners' attention and availability.
However, these 30 to 60 minutes should not become 30 to 60 minutes of passive content consumption. Their value lies precisely in what can happen during that time: explanations, conversations with the tutor, questions, realistic scenarios, feedback, and moments when learners must actively apply what they have just learned.
For more complex skills, it may therefore be more effective to plan several sessions of this length, potentially spaced over time, rather than trying to compress everything into a single multi-hour learning experience.
The most useful question is therefore probably not simply:
“How long should a training session be?”
It is also:
“What are we actually doing with the time our learners give us?”
📚 Sources
Sweller, J. — Cognitive Load Theory
Cepeda, N. J. et al. — Distributed Practice in Verbal Recall Tasks: A Review and Quantitative Synthesis
Dunlosky, J. et al. — Improving Students’ Learning With Effective Learning Techniques
Freeman, S. et al. — Active Learning Increases Student Performance in Science, Engineering, and Mathematics
Brown, P. C., Roediger, H. L. & McDaniel, M. A. — Make It Stick: The Science of Successful Learning
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