Scientists Let Fish Choose Their Perfect Partners Through Nine Generations of Virtual Dating

Scientists have created a virtual dating experiment that allowed green swordtail fish to repeatedly choose their preferred partners, revealing how different preferences can shape the appearance of potential mates over several generations.

Researchers from the University of Exeter placed individual fish in tanks with screens on both sides. Each screen displayed a different virtual fish, allowing the researchers to measure which potential partner attracted more attention.

A Dating Game for Fish

The experiment involved 11 female and 12 male green swordtails.

Each fish was given three minutes to choose between two virtual partners. Researchers measured the amount of time the fish spent near each screen to determine which one it preferred.

The preferred virtual fish was then used to create new digital candidates for the next round.

By repeating the process, scientists effectively created nine generations of virtual fish whose characteristics were gradually shaped by the animals’ choices.

Males Had a Clear Preference

Male swordtails consistently showed a preference for larger females.

As the experiment progressed, the virtual females became increasingly larger. By the ninth generation, they were more than 24 percent larger on average than the virtual females presented during the first generation.

Researchers say the preference may be related to the fact that larger females can potentially produce more offspring.

Female Choices Were More Varied

The female fish produced a much more complicated pattern.

Different females appeared to favor different characteristics, including tail length, body size, coloration and patterns.

One female even repeatedly selected virtual males that became increasingly similar in appearance to females.

The researchers said they do not yet know exactly why that happened. One possibility is that the female was avoiding physical characteristics associated with threatening males.

Why Use Virtual Fish?

Studying mate preferences in real animals can be difficult because researchers can only present a limited number of possible partners at one time.

The new system allowed scientists to generate thousands of combinations of characteristics and let the fish effectively “design” the type of partner they preferred.

Computer algorithms created new virtual fish using characteristics from previous winners, allowing the researchers to observe how preferences changed over successive generations.

A Shortcut for Studying Evolution

Normally, observing how mate preferences influence traits over generations could take many years.

The researchers say their virtual approach provides a much faster way to study sexual selection, the evolutionary process in which certain characteristics become more common because they make an individual more likely to be chosen as a mate.

The method could potentially be adapted to investigate mate preferences in other animals that respond to images or videos of members of their own species.

What the Fish Experiment Reveals

The study shows that there is not necessarily one universal idea of an attractive partner, even within the same species.

Male swordtails in the experiment showed a relatively consistent preference, while individual females displayed considerably more variation.

Researchers hope that experiments like this will help scientists better understand how animal preferences influence the evolution of physical traits over time.

The study was published in Royal Society Open Science on September 29, 2026.

Sources

• University of Exeter — “Fish choose perfect partners in dating game study” — September 29, 2026.
• EurekAlert! — “Fish choose perfect partners in dating game study” — September 29, 2026.
• Phys.org — “Nine generations of virtual dating reveal how fish shape their ideal mates” — September 29, 2026.
• Royal Society Open Science — “Exploring male and female mate preferences using genetic algorithms and digital phenotypes” — September 29, 2026.