The figure (positive space) and ground (negative space) principle is probably the most difficult one to understand. In terms of design, the figure refers to the object and the ground is the background. When looking at a visual element, people tend to look for ways to differentiate between the figure and the background.
1-Size: Images and visual elements that appear to be larger will be perceived as closer and as part of the figure.
2-Contrast: Use of high contrast can lead people to differentiate between the figure and the ground.
3-Blurriness: A blurred or out-of-focus element will give the effect to be the background.
The figure and ground principle can be used to create illusions in design.