Sometimes we tend to think of our brains like a very complicated computer hard drive. When you first buy one, it’s a clean slate waiting for data to be dumped onto it over time. But is that actually true for a human brain? Are babies born as empty storage devices waiting for life to install software onto them? Or do our brains arrive with some information already preloaded, like naturally occurring bloatware?

According to a recent study of mice published in Nature Communications, the answer may lean closer to us coming home fresh from the factory with some preloaded bloatware on board.

Researchers at the Institute of Science and Technology Austria studied mouse brains from birth through adulthood, focusing on the hippocampus, the memory-processing part of our brain. They found that newborn mouse brains already came prepackaged with a densely packed network of neural connections. Instead of building complexity over time, the brain seemed to begin at max capacity before gradually trimming itself down to a more efficient bandwidth.

This means that your brain isn’t a blank notebook, waiting to be written on by life. It’s more like a densely packed jungle that gets naturally pruned back over time.

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The researchers focused on CA3 pyramidal neurons, which help process spatial memory and turn short-term memories into long-term ones. In newborn mice, these networks were a disconnected, disorganized mess. But as they grew older, the unnecessary connections were severed entirely, leaving behind a more optimized system.

There’s a bit of logic to this, the researchers argue. Building a functioning brain from scratch would be extremely, painfully slow if every neuron had to find and connect with every other neuron individually. It’s a lot faster to start off with way too many fully connected neurons and then just cut away the ones that are unnecessary and keep the ones you actually need.

Of course, this was a study of mice. For as much as they are like us, physiologically, there are still big enough differences that it’s not a one-to-one comparison. But it’s a nice starting place to one day figure out if we also come into the world with a brain overloaded with connections that get cut away over time, or if maybe our brains are blank Word docs that we load with valuable information.