In decades of films, the dead have risen from the grave to stalk the living. Classic zombies go slow (a literal plodding approach of death), while modern zombies are often swifter, sometimes speedy. Though science-fiction fans will endlessly debate which is better, a new neuroscience study on the closest thing we have to zombies in real life—those who rise from the dead of sleep—finds they tend to be the snappy kind.

In a small study published Monday in Current Biology, researchers found that sleepwalkers tended to have better locomotor control and awareness than those who don’t wander while out cold. Specifically, researchers gave study participants (when they were awake) a movement test and a mental task to do at the same time. Even though the mental task was known to interfere with motor control, the sleepwalkers could still complete the movement test with the same accuracy and at their normal, brisk pace. But the extra brain work tripped up the non-sleepwalkers: they lurched through the movement task, even though they could perform it quickly when not mentally distracted.

The finding has two main takeaways, the authors argue. First, it hints that the brains of sleepwalkers may be better wired to automate locomotor control and awareness, freeing the body to move about without full consciousness. Secondly, it suggests that there may be waking behavioral tests that potential sleepwalkers could take to help determine if they have the sleep condition.

But for now, the takeaways are just preliminary hypotheses. The study was small, involving only 11 sleepwalkers and 11 non-sleepwalkers (who were age- and gender-matched to the sleepwalkers). Also, the study was only “single-blind,” meaning that although the participants didn’t know what was going on, the researchers knew which patients were sleep-walkers. This could unintentionally introduce bias to the experiment and analysis. A single-blind study is opposed to the gold-standard “double-blind” type, in which both the researchers and the participants are in the dark to avoid any bias.

Still, the authors, led by neuroscientist Olaf Blanke of École Polytechnique Fédérale de Lausanne in Switzerland and cognitive neuroscientist Oliver Kannape at the University of Central Lancashire in the UK concluded:

Although the present data should be regarded with caution (sample size; single-blind design), we argue that the experimentally induced wakeful locomotor state in the present sleepwalker cohort bears resemblance to their nightly walking episodes in the absence of full consciousness. Our findings link sleepwalkers to the neuroscience of locomotor control and awareness and characterize a potential behavioral marker of sleepwalkers during full wakefulness that only becomes overt while walking under cognitive load.

Zombie mind

To test the locomotor and awareness skills of the nocturnal nomads, Blanke and colleagues had them perform a walking task through virtual reality while their real body movements were tracked in a motion-capture area. The walking task was simple: they just had to walk their VR avatars 1.8 meters to a tall, virtual cylinder. Each participant did this 88 times in a row. Twenty-four of those times was with an accurate VR experience. That is, their avatar’s movement matched theirs. Then, they did four sets, each with 16 repetitions, where their avatar’s movement was purposefully skewed to the left or right of their actual movement—by 5, 10, 15, or 30 degrees—and the participant had to account for that. The control participants did the same 88 trials.

In each trial, the researchers tracked the participants’ velocity. And after each run-through, the participants had to rate whether they thought their avatar’s movement was skewed.

Next, the participants did the whole thing again. But this time, they had to do the 88 walking tests while serially subtracting seven from 200 out loud—200, 193, 186, 179, etc. This is a task that researchers have repeatedly shown to interfere with locomotor control, altering the manner and pace of steps.

Here’s how the subjects did: in the first block of 88, when they just had to walk, both groups did about the same at velocity and assessing the skewed trials. But, with the mental task, the sleepwalkers took the lead. They kept the same velocity they had in the first block, whereas the non-sleepwalkers slowed down while counting.

Subjects were asked to note how much their avatars’ movements were skewed while they were walking and counting versus when they were just walking. The sleepwalkers were just as good, if not slightly better, at knowing the difference. But the non-sleepwalkers fared worse. They overestimated the amount of skewing while they were counting and walking.

Though there’s much more research to do to back up the findings, the authors are hopeful that the data is headed toward a better understanding of and diagnostics for sleepwalking.

And if the research holds up, it suggests that, in the event of a zombie apocalypse, sleepwalkers may have a brainy advantage.

Current Biology, 2017. DOI: 10.1016/j.cub.2017.08.060 (About DOIs).