Guppies Raised on Screens Develop Brain Abnormalities

The debate regarding the impact of screen time duration on child brain development has gained a new perspective. A recent study from the Department of Zoology at Stockholm University, Sweden, has revealed surprising facts through trials on guppy fish (Poecilia reticulata). Young fish that interacted only through video screens experienced brain development similar to fish living in total isolation.

The study, led by Olivia Carmstedt for her master’s thesis, intentionally chose guppy fish due to the high flexibility of their brain development. “Fish are an excellent model for studying brain plasticity because their brains continue to develop throughout their lives,” explained Professor Niclas Kolm, the senior author of the research.

In the experiment, which lasted 20 days, researchers divided young guppies into three different environmental conditions. The first group was placed next to an aquarium containing live fish that they could see and interact with. The second group was presented only with video recordings of other guppies via a monitor. Meanwhile, the third group was raised in conditions of almost total isolation without any companions.

All environmental variables were kept exactly the same, ranging from food and water quality to lighting. The only difference was the type of social stimulation they received. The second group, which watched the videos, actually received the same visual information as the first group, but they lacked the two-way feedback aspect of real interaction.

When the research team measured the brain volume of the fish, the results were astonishing. The group of fish growing alongside live companions had a brain size almost 6% larger than the group that only watched screens. Additionally, this direct interaction group also developed a much larger olfactory bulb.

The most surprising finding for the researchers was the condition of the screen-watching group. Instead of falling somewhere between the direct interaction group and the isolated group, the brain structure of the guppies watching the screens was almost identical to those raised in total isolation.

“Interaction itself—the fact that another individual responds to you in real-time—appears to be vital for normal brain development,” stated Carmstedt. Watching visual content alone proved not to provide the same impact as real interaction.

Nevertheless, these differences in brain size did not affect their basic non-social cognitive abilities. When tested using an object permanence test—the ability to track a target that has disappeared from view, similar to a baby understanding a hidden toy—all three groups performed equally well. This indicates that social experience specifically shapes certain brain areas, rather than overall intelligence.

While humans are not guppy fish and these results cannot be directly applied to the impact of tablets on toddlers, the findings provide an important analogy in the screen time debate. This study suggests that the quality of interaction is far more important than the quantity of visual information. Two-way video calls with family members, where there is reciprocal real-time response, are thought to provide much better stimulation for the developing brain than merely watching passive, one-way broadcasts. The research has been officially published in the journal Biology Letters.