Originating from Gestalt theory, a Gestalt shift is when someone's interpretation of his experience changes from one thing to another. The famous duck/rabbit illusion provides a simple example: the moment one's brain switches from seeing the image as a duck to seeing it as a rabbit represents a Gestalt shift.
Gestalt shifts are not limited to changes in the perception of physical phenomena, they can also occur in the intellectual, emotional and spiritual realms of human experience. Consider, for example, an adult who just had an emotional experience of "letting go" of his anger toward his parents and forgiving them for grievances he previously held regarding his upbringing. An event like this might trigger a broader shift in that person's overall interpretation and valuation of his relationships with his parents or even with others in his life. This is a Gestalt shift.
Named after a German word that roughly translates into "shape" or "pattern," the Gestalt theory of psychology originated in the early 1900s in Austria and Germany. It was a response to the prevailing atomistic view of psychology of the time that emphasized the scientific analysis of the individual parts in order to understand a whole. Gestalt theory, in contrast, emphasized the concept that the whole is more than the sum of its parts and was an effort to introduce a more humanistic approach to understanding human psychology.