The most commonly used rationale for reference pricing is Helson’s AdaptionLevel Theory (1964).
Adaptation level theory describes the process by which a person becomes insensitive to the effects of constant stimuli. This theory is based on the assumption that the initial effect one experiences, upon exposure to an unchanging sensory stimulus, quickly dissipates with time. The past and present experiences define the adaptation level or reference point, leading to seeking new stimuli for comparison and perception