Automatic duplication of layers while dragging them across the page

I just installed the newest Photoshop. Now whenever I drag an image across the page to move it, it duplicates the image, as if I'm holding down the Alt key, which I'm not. It only duplicates the layer once, but there are two versions of the same image on the layer now. 

Also, I can only then move the "new" duplicated image, while the old one stays where it is. A new layer is not created.