Genetics

Nature, Nurture...Neither? Why Individuality Might Be Unavoidable

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It's one of the most hotly debated questions in science: is personality nature or nurture? That is, is it your genetics or your upbringing that makes you, you? Research into a certain fish species, of all things, suggests that even when both are virtually identical, you can still have personality differences. In essence, the study says this: you're a special snowflake. Deal with it.

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Carbon Copy Amazon Mollie

For a study published in May 2017 in the journal Nature Communications, researchers from the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) took a look at Amazon mollies. They chose this species of fish because they're natural clones: all of the offspring from a single mother shares the exact same genetic material. They placed these newborn mollie clones in three different setups. In the first, each fish was kept individually from each other from birth, but in identical conditions. In the second and third setups, the fish lived in groups of four for one or three weeks, respectively, then were separated.

At the end of seven weeks, the researchers examined each mollie to see how their personalities differed. (In fish terms, personality equates to activity level and exploratory behaviors.) They found that across the board, the fish ended up with distinct personality differences—regardless of the fact that they were genetically identical animals raised in identical environments.

Tiny Differences Make Big Changes

How is this possible? Clearly, there had to have been some differences. But the impact those tiny differences had was still very surprising to the researchers. "Our results suggest that other factors must influence the development of personality in a more substantial way than previously thought," behavioral ecologist and co-author Kate Laskowski said in a press release. Maybe those were tiny differences in temperature from one side of the tank to the other, or the angle the light took in the water. The differences could also be epigenetic; that is, changes in the way certain genes are expressed. What's clear is that personality is much more variable than we thought. Even when we think we can control it, it finds a way to foil us.

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Key Facts In This Video

  1. Trait theory researchers try to define personality by looking at long-term behavior patterns and conscious motivations. 02:00

  2. Reciprocal determinism theorizes that aspects of your environment affect aspects of your personality, and vice versa. 05:13

  3. The humanistic approach generally disregards methods of standardized personality testing. 09:01

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