Is the inner shape a real circle?
Sometimes extraneous information around your target can distort your view. Try covering the lines with a piece of card to remove some of the interfering information.
Here you are exercising your visual perception and decision-making skills. The visual cortex in your occipital lobes processes visual input from your eyes. Not only is the occipital lobe mainly responsible for visual reception, it also contains association areas that help in the visual recognition of shapes and colors. Problem solving, selective attention, and executive functions used in this exercise are handled by the anterior portion of the frontal lobes.
Both shapes are perfect circles.