What phenomenon occurs when the grey circle around a fixated plus sign disappears due to continuous fixation?

The phenomenon where the grey circle around a fixated plus sign disappears due to continuous fixation is referred to as sensory adaptation. This occurs when sensory receptors become less sensitive to constant or unchanging stimuli over time. In the context of visual perception, when a person fixates on a particular stimulus, such as the plus sign, the visual system adapts to the unchanging background (the grey circle) and effectively reduces its response to it. As a result, the grey circle may seem to fade away or disappear from conscious perception because the visual system no longer prioritizes it as a relevant stimulus.

Sensory adaptation is a common experience across various sensory modalities, as it allows individuals to focus on changes in their environment rather than being constantly aware of unchanging stimuli. This adaptation is crucial for efficient sensory processing, facilitating attention toward new or dynamic stimuli while ignoring stable objects that do not provide additional information.