Craviatior,
As a private pilot you are trained to look out of the window at the picture. It's as advertised - Visual.
If you take a visual only pilot and stick them into a cloud, there is a high probability that they will believe whatever their body (inner ear) is telling them. And that will normally induce spacial disorientation.
When I was working on my instrument rating, my instructor took me up, put the hood on, and made me take my hands and feet off the controls.
He spent a matter of 90 seconds turning, climbing, descending and then asked me what attitude the aircraft was in without looking at instruments or outside.
And boy was I wrong. Every time. It's to do with the inner ear and how we balance.
As Di-Vosh says, if you are not an instrument pilot, you will find it very hard to switch from outside the plane to the instruments. Trust me, been there, seen it, done it, changed underwear and prayed to the gods of all things in the air to save me.... And been lucky. Never did that one again.