Dating identical twin
After three months, all the mice had grown more active and adventurous.
But though the mice at the start all demonstrated a similar level of wanderlust, by the end of the experiment their travel patterns were decidedly different.
Researcher Julia Freund and colleagues at various German universities began with 40 genetically-identical young female mice.
These mice were housed in a custom-built mouse paradise: a cage with five levels, tubes to climb through, boxes to hide in and toys throughout.
Even our friends, who could easily tell us apart, sometimes referred to us as the twins rather than using our names.
I think some of it is just people's laziness, not bothering to recognise and develop separate relationships, but I think some of it is also because twins have such a close bond that it sort of shuts other people out.
While some mice hung around a home area and occasionally ventured outside their comfort zones, others spent equal parts of time in all the cage’s corners.
For identical twins, people not bothering to, or not being able to, distinguish between them is likely to reinforce the twins' tendency to be seen as a unit (the twins) rather than as two unique individuals.
At a simple level, biology says you’re a product of your genes and your environment—or, nature and nurture.
But the explanation is trickier when you consider identical twins raised in the same home: they have the same genes, and grew up in the same environment, but, if you’ve ever met a pair you’d probably agree, they’re different people.
Identical twins often experience this stage very differently from singletons.
For twins it's not an "I" stage but instead, a "we" stage, where twins learn to distinguish only so far as "us" and "them" creating a unit style identification.