Are we shaped by social experiences in the earliest phase of life?

It is widely accepted that our childhood social experiences shape our behavior as adults, and that events we may not even remember can have lifelong effects. A recent study from the Champalimaud Centre for the Unknown is shedding new light on this phenomenon, suggesting that the very earliest stages of life have the greatest impact on behavior.

Experiments with zebrafish revealed that social experiences during the first week of development impacted future behavior. The fish are not even considered social at the larval stage, so this was completely unexpected. 

“Social experiences greatly define subsequent social behavior. Lack of such experiences, especially during critical phases of development, can severely impede the ability to behave adequately in social contexts,” wrote the researchers. “To date, it is not well characterized how early-life social isolation leads to social deficits and impacts development.”

For the investigation, zebrafish larvae were raised either in regular groups or alone in a dish. Later, high-speed video tracking was used to precisely measure swim movements as the fish interacted.

“It was previously thought that the effects of early-life social experience could only be seen at an age when the animal shows attraction to social stimuli, but we have shown that, in zebrafish, the effects can already be observed earlier,” said study lead author Antonia Groneberg. 

“Normally, larvae move away from other close-by larvae, but we have found that larvae raised in isolation tend to react with a stronger escape swim, even when the other larvae are located at a larger distance.” 

“By removing inputs from different senses and testing artificial stimuli that mimic another fish, we found that isolation-raised fish showed stronger reactions to local water vibrations.”

In the next phase of this project, the researchers will study the brain activity of the zebrafish. “Using live imaging, we can record activity throughout the whole brain, from areas that process sensory stimuli to those that control behavior,” said study co-author Michael Orger. 

“We are working towards a framework of collective behaviour in which we include the information on how the brain processes the information about the environment and about neighbouring conspecifics,” added principal investigator Gonzalo de Polavieja.

The study is published in the journal Current Biology.

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By Chrissy Sexton, Earth.com Staff Writer