Gallimore (2002) discussed the ongoing concern with appraisal inaccuracy, describing appraisal as making use of the lens model from cognitive psychology. This model describes the situation where people have to make judgments about an event without the benefit of direct observation. The inability to see the event might be because it will occur in the future (such as the reversionary value of a brownfield).
Gallimore notes that such a person making the judgment has to rely on various indicators of the outcome of the event - what the model refers to as cues. These 'cues' form the 'lens' through which the person making the judgment attempts to see the outcome. The lens model implies that the accuracy of an appraisal relies on three factors:
the inherent predictability of events in the environment as reflected in an "environmental" forecasting model (such as using econometrics or the Triad process).
the match between the forecaster's (appraiser's) model and the environmental model
the consistency with which the forecaster (appraiser) applies his or her model
But appraisers don’t use such models. They rely on sales of other property subject to an intangible-indemnification. They cannot see (or model) the future sales price of the property or the movement of the contaminants in the subsurface and their potential effect on the health of area residents, so they cannot solve Problem 1 or Problem 2 or know if a buyer is well-informed. The research presented in Weber (2005) should help to provide a foundation for appraisers, so the field can progress from an art to a science, and so their trade can progress to a profession, per Canonne and Macdonald (2003).