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CORPITORAT LAL Engineering Division Memorandum Report Noe MC REXD=69l.-18D 26 April 1919 These conditions are largely lacking in the case of the data available on unidentified flying objects. It is impossible to say with any assurance what any partioular individual in this series of 2¥2 reports was actually observing at any particular time, t is only possible © to examine the accumulation of available evidence or the acowulation of all reports of a riven class (e.¢., all rerorts from supposedly conpetent observers) and to consider them in a statistical sense. If certain characteristics appear repeatedly in reports fren different people it may be possible to infor causal factors. It will never be possible, on the other hand, to say with certainty that anv given observer could not have seen a space ship or an ememy missidie, or some other object. It will only be possible to estimate ¢ the prohability thet he could have seen such thingse The principal hypothesis to be examined in the following dis oussim © is thet reports of unidentified flying objects have the characteristios that would be expected if they were cases of failure, on the part of typical normal individuals, to identify oonmon or familiar phenomena. Possible Sources of Inacourate Reports of Flying Objects Stich tse es at There are three broad classes of mistakes in human observations. These are the following; 1, Misinterpreting the nature of real stimli, 2, Mistaking unreal (imaginary) stimuli for real ones, and 3. Del berate falsifioationse Each of these are considered briefly bolo. (1) Brrors in Identifying Roal Stimli. All nornal, a helen = intelligene people experience certain errors of observation, The moon appears much larger on the horizon than when it is high in the () skye A stick looks bent when one end is in water. Distant objects appear relatively close in clear, desert atmosphere. A small point~ source of light, if viewed in a dark roam, will appear to move about in Declassification Authority: NND 57565