How to give an effective presentation: slides that build up as you speak guide the eye

How do you give an effective presentation when you use slides? A study from Tokyo University of Science, published online on 25 June 2026 in the Journal of Computer Assisted Learning, suggests a very simple answer: show information one piece at a time, at the moment you talk about it, instead of putting up the complete slide straight away.

It sounds like a technical detail, and partly it is. But it touches on something anyone who presents a project, an offer or a set of results knows well: while you are speaking, where is your audience looking?

What the researchers did

Hikaru Ito and Hiroko Ichikawa, of Tokyo University of Science, call this format a “cumulative presentation”. Each element of the slide, a bullet point, an illustration or a chart, appears at the moment the speaker starts explaining it. Elements already shown stay visible, so the full picture builds up in front of the audience.

To test it, the researchers compared two versions of the same recorded lesson: one in which the elements appeared together with the explanation, the other with the whole slide visible from the start. During the lesson they recorded every participant's eye movements with an eye-tracking system.

Here are the main figures from the experiment, as reported by the study and the university's press release. Each one measures a single thing.

• 40 Japanese university students, split into two groups of 20.
• A biology lesson of about 20 minutes, spread over 7 slides, with the teacher's voice.
• A test before the lesson to measure prior knowledge, and the same test right after it.
• A measure of gaze: how soon and for how long each person looked at the element the teacher was talking about.

What the study found

The group that saw the cumulative presentation did better on the final test. The effect, measured with a statistical index called Cohen's d, was 0.49: a medium-sized effect, real but not huge.

The clearest differences concern gaze. Those who saw the elements appear along with the explanation found them sooner with their eyes (d of 1.76) and looked at them for longer (d of 1.15). These are large effects: in practice, when the slide was already complete, the audience had to search the screen for the thing being discussed, losing time and attention in the search.

The authors are clear about the limits. The sample is small and comes from a single university. There was only one lesson, on biology, and the final test measured what people remembered straight afterwards, not weeks later. So the study does not say that build-up slides always work: it suggests that, when the content is dense, guiding the eye helps people follow.

Why a complete slide scatters attention

Presenters tend to assume the audience listens first and looks second. Often the opposite happens: as soon as the slide appears, eyes scan all of it, read ahead and settle on a chart while the speaker is still on the first point. At that moment voice and image are telling two different stories, and the listener has to choose.

The study puts a concrete measure on this mismatch. The point is not just whether the audience looks at the screen, but what they look at while you speak. That is where the difference lies between a presentation people follow and one they simply sit through.

How to give an effective presentation with slides

The format studied can be created with any presentation software, using the simplest appear animations. It is worth using with judgement, though, not on every slide.

• Show one idea at a time and bring it up the moment you mention it.
• Keep the points already explained on screen, so the audience can see the thread of the argument.
• Save gradual reveals for dense slides: charts, diagrams, comparisons.
• Avoid showy motion effects, which draw the eye to the animation instead of the content.
• Look at the audience, not the screen: the slide supports your voice, it does not replace it.

In the university's press release, Ichikawa stresses that simply releasing information in small doses, even on existing slides, makes it easier to follow. Knowing your audience still matters: in front of people who have already read the figures, a summary slide may work better.

Slides, voice and presence: one message

An effective presentation does not come from the slides, but from the match between what you say, what you show and the way you move in front of people. The Japanese study shows that simply synchronising image and word brings the audience's eyes to the right place sooner.

With the Com-On programme, CG Imagine works on exactly this synchrony: slide structure, vocal rhythm, posture and gesture, so that your listeners look at what you are talking about at the moment you talk about it, and do not have to search for it on their own.

Photo by Vitaly Gariev on Unsplash