At first glance, it's a simple video of a dancer spinning. However, in fact it is an optical illusion that some say could actually reveal how smart you are.

乍看，这是简单的舞者旋转视频。然而，事实上，这是种光学假象，有些人说这能体现出你有多智慧。

It plays with the brain's visual perception - some see her spinning clockwise, counterclockwise or even switching between the two.

这玩的是大脑的视觉感知，人们会看出舞者按顺时针、逆时针旋转，甚至有人看出在两种旋转方式间切换。

For years, the rotating figure was used to test intelligence and determine which side of the brain was more dominate. Now, experts say it isn't about brain hemispheres, but most will see the dancer rotate clockwise because we tend to have a viewpoint from above and an attentional bias towards the right side of the body.

多年来，这一旋转的身影用来测试智力，决定哪边大脑占主导。如今，专家称这无关左右脑，但多数人看到舞者顺时针旋转，因为我们容易根据所言形成观点和对右边人体形成注意偏向。

There is are much more complex reasons behind why we see her spinning in different directions.

缘何我们看到她在不同方向旋转，其后有更复杂的原因。

And the reason for the uncertainty is because these kinds of optical illusions do not reveal any clues about the image's depth to help us make sense of it. When images aren't clear, your brain takes the initiative to fill in the gaps where information is missing.

不确定的原因在于这些光学幻象并没有透露任何图像深度的线索以助我们有所意识。图像不清晰的时候，你的大脑主动填补信息的不足的空白。

However, a video adds small white contour lines in certain areas of the dancer's body, which allows our brain to 'solve the illusion faster'.

然而，有个视频给舞者身体特定部位加上些许白色轮廓，让我们大脑“更快速解决幻影问题”。

This is because your brain is able to gather more information from what is being presented.

这是因为大脑可以根据眼前所呈现的收集更多信息。

And a study from 2015 says another reason for our clockwise bias, which is an attentional bias - humans tend to lean towards the right side of the body and that the area of our brain that deals with fear, rage and panic – the subcortical system.

2015年的研究称，我们的“顺时针偏见”另有一原因：人类倾向于向身体右方倾靠，还和我们大脑处理恐惧、愤怒和惊慌的部分即皮层下体系有关。