Final answer:
Perceptual completion, or closure, is the phenomenon where our brain fills in missing information based on limited sensory input. In the case of the green square and blue circle, participants might report seeing a green circle.
Step-by-step explanation:
The phenomenon described in the question is called perceptual completion or closure. This occurs when our brain fills in missing information or makes assumptions based on limited sensory input. In the case of the green square and blue circle, participants might report seeing a green circle because the brain perceives the incomplete information and fills in the missing part.