Interpersonal neural synchrony can strengthen during a shared task and then change. This is especially interesting in an intergenerational pair. In the creative process itself, it can be imagined like this: one participant sets a direction, the other develops it; one holds their own line while the other responds to changes in the shared pattern. Initiative can pass back and forth, and the mode of interaction can be reconfigured. Therefore, an averaged measure of synchrony may conceal the main thing—how the very architecture of interaction changes over time.
A new study by ETH Zurich shows this especially clearly using the example of joint drawing by people of different generations. During the shared work, their neural activity did indeed become more coordinated than during individual drawing, yet over the course of six sessions the trajectories diverged: among the young participants who worked with peers, synchrony increased, while in the mixed-age pairs it decreased. At the same time, the subjective sense of social closeness grew in both groups, showing that increasing closeness and changing neural synchrony can occur simultaneously.
This produces a paradox that makes the study far more interesting than a simple story about two people gradually “tuning in to each other.” If closeness grows, why does neural synchrony not necessarily grow along with it? And can joint creativity create a unity of process precisely without the constant matching of two nervous systems?
Joint drawing as a laboratory of interaction
The study by the Social Brain Sciences Lab at ETH Zurich was published on 20 August 2026 in PLOS Biology. It involved 122 people, combined into 61 pairs: 30 pairs of young adults of the same generation and 31 intergenerational pairs, in which a young participant (18–35 years old) worked with an older participant (69+ years old). All began as strangers and met six times over six weeks.
At each session, the participants first drew on their own and then together created a drawing in oil pastel. They were not given a theme and were not told what the result should be; during the drawing they did not talk. Cortical activity was simultaneously recorded in both participants using fNIRS—a method that makes it possible to observe the dynamics of neural processes during relatively free movement.
The first result was unequivocal: joint drawing was accompanied by higher interpersonal neural synchrony than individual drawing. The very fact of a shared creative task did indeed change the way activity was coordinated between the participants.
But the most interesting part began not at the moment of comparing “together” and “separately,” but when the researchers looked at how this coordination changed from session to session.
In different generations, synchrony moved in different directions
In pairs of young people of the same generation, interpersonal synchrony increased over time. In the mixed-age participants, the opposite trajectory was observed: the measures were higher in the early sessions and then declined. At the same time, the subjective sense of social closeness increased in both groups.
This fundamentally changes the question itself.
If neural synchrony were a direct reflection of closeness, it would be logical to expect it to rise steadily along with the relationship. But the data do not show this. Moreover, the authors emphasize the multi-component nature of interpersonal synchrony: its different patterns are linked to different aspects of social connection, and their dynamics may differ depending on generation and situation.
Therefore, the decline in the measure among intergenerational pairs does not mean that the participants became less coordinated. Rather, it reflects a change in the character of synchrony: certain temporal coincidences of neural activity became less pronounced.
And this leaves room for a far more interesting picture: a shared process can continue and become more coordinated even if the two nervous systems do not display ever greater direct synchrony.
The changing architecture of interaction
It was precisely this question that the researchers continued to study in a separate paper published in September 2026 in the journal Acta Psychologica. Luca A. Naudszus, Ryssa Moffat, Emily S. Cross. Instead of a single average measure, they examined interaction as a sequence of states, simultaneously tracking the connection within each participant and between the two participants.
This approach revealed seven recurring “two-brain states.” Three of them were characteristic specifically of real pairs, rather than of artificially assembled pseudo-pairs. At the same time, none of the states showed a sustained change in duration from the first meeting to the last.
This is an important detail. It means that a relationship cannot be described by a simple sequence: first people are poorly attuned, then they understand each other better and better, and their neural activity gradually begins to coincide more and more strongly.
In reality, the configuration is constantly changing.
At one moment the participants may both be orienting themselves toward the shared drawing. At another, one person becomes more strongly absorbed in their own action while the second responds to changes in the space. Then the roles may switch. What, when averaged, looks like a single measure of synchrony turns out, within the process itself, to be an alternation of different modes.
When initiative passes from one participant to the other
One of the discovered patterns proved especially interesting for the mixed-age pairs. During joint drawing it persisted longer in them: the connection between the participants was low or moderate, whereas within the nervous system of one of them there was pronounced coherence between two regions of the inferior frontal cortex. This mode was also accompanied by a smaller number of alternating actions.
The authors regard it as a possible example of asymmetric interaction — a situation in which one participant organizes the action to a greater degree, while the second adapts to it. This does not mean constant leadership: the point of the analysis is precisely that such roles can change within a single task.
For joint drawing this is easy to imagine.
One participant draws a line. It changes the space on the sheet and thereby creates new possibilities for the second. The latter may continue the movement, alter it, respond with a separate element, or leave an empty space. A few moments later, the initiative may pass back.
Here coherence does not necessarily arise from simultaneity. It can be built on a sequence: action — perception — response — new action.
It is precisely this view that makes the concept of synchrony far deeper.
How age affects the dynamics of synchrony
The age difference is especially interesting because the participants come to the shared task with different experience and different ways of perceiving what is happening. At the same time, the study does not claim that age in itself determines neural dynamics: the work was exploratory, and the specific mechanisms of the differences require further study.
But the difference in trajectories remains an important result.
In young pairs, joint activity was accompanied by a gradual increase in interpersonal synchrony. In intergenerational pairs, it was accompanied by a decrease in a number of areas, especially those associated with the right temporoparietal region. At the same time, the feeling of closeness grew in both groups.
It turns out that the same social outcome can be accompanied by different neural dynamics.
This is more important than the mere question of who has “higher” synchrony.
Synchrony as a changing process
Let us imagine two people drawing together for five minutes. During this time, one of them starts a new movement several times, the second responds; then the first stops, and the second continues; then both simultaneously focus on different parts of the image.
If everything that happens is reduced to a single number, most of this story will disappear.
That is precisely why the second analysis is important methodologically. It shows that the connection between two participants cannot be fully described by an average value: one needs to see when, where and in what configuration coherence arises. At the same time, both the connection between the participants and the organization of processes within each of them can change.
In such a reading, synchrony becomes not a state of “we are working in the same way,” but a dynamic mode of coordination.
Sometimes two participants really do turn out to be neurally more coordinated. Sometimes one acts more independently, while the second orients toward them. Sometimes a more pronounced organization arises within one nervous system while the interpersonal connection remains relatively low.
And all of this can happen within the same drawing.
The unity of the process through various actions
Here an especially interesting conclusion emerges — already at the boundary between science and art.
Joint work does not necessarily become unified because two systems gradually begin to function in the same way. It can become unified thanks to the fact that various actions begin to work within a single process.
This is clearly visible precisely in the intergenerational pair. One participant can create a direction, the second can develop it. One can hold their own line while the other reads the changes in the shared space. Initiative can pass from one to the other, and the mode of interaction can be restructured.
At the level of individual indicators, this looks like a changing, sometimes decreasing synchronisation. At the level of the creative task itself, it looks like a continuous coordination of actions around a single emerging work.
The study does not prove that a decrease in interpersonal synchronisation causes such unity. But it shows why these two concepts cannot be equated.
Flexible coordination instead of complete coincidence
The main value of these works lies precisely in the fact that they expand the popular image of two people who gradually “tune in to the same frequency.”
Interpersonal neural synchronisation can increase during a shared task and then change; the connection between two participants can be combined with a strengthening of internal organisation in one of them; interaction can be symmetrical or asymmetrical; initiative can pass from one person to the other. And the more attentively researchers look at the temporal structure of the process, the less it resembles a simple movement toward complete coincidence.
Perhaps this is precisely why joint creativity turns out to be such an accurate model of human interaction.
Two people are not obliged to think alike, move simultaneously, or constantly demonstrate high direct synchronisation. They need something else — to remain sensitive to changes in the shared process and to respond flexibly to the partner's actions.
And then the shared drawing becomes not the result of ever greater similarity, but the trace of a living coordination: of the way two independent systems find new ways of acting within a single creative space.
