Engineering Division
Memorandum Report No. ECREXD-691-18D
25 April 1949
UNCLASSIFIED
APPENDIX A
PSYCHOLOGICAL ANALYSIS OF REPORTS OF
UNIDENTIFIED AERIAL OBJECTS
I
The Inaccuracy of Human Observation
Psychologists have long known that human perception is fallible. In fact, part of the science of psychology is concerned with the measurement of errors of observation, and with the discovery of the conditions and laws that govern such phenomena.
Errors of observation may be classified as *variable* or *constant*. *Variable errors* are those in which a number of separate observations are found to differ from one another. The distribution of such errors often follows the normal probability curve. *Constant errors* are those in which observations are consistently biased in one or another direction. For example, individuals often are guilty of a constant error, in the direction of underestimation, in reporting their ages.
Errors of observation may be classified further as *precision errors* and *identification errors*. Inaccuracy in estimating the speed of an aircraft is an example of the former. Mistaking an aircraft for a "flying saucer" is an example of the latter.
It is the purpose of the present report to analyze 212 reports of observations of unidentified flying objects in order to see to what extent these reports can be explained in terms of known psychological facts and principles.
Scientific Method and a Posteriori Data
A word of caution must be injected at the outset of this report. Certain conditions are necessary for drawing valid scientific conclusions.
DOWNGRADED AT 12 YEAR INTERVALS; NOT AUTOMATICALLY DECLASSIFIED. DOD DIR 5200.10
UNCLASSIFIED