12-7] IMPORTANT CHARACTERISTICS OF THE HUMAN OPERATOR 649 



Fig. 12-31 shows the results of a study on the amount of information 

 absorbed as a function of the rate of presentation and the mode by which 

 the subjects transmitted the information to a recorder. ^ In this study the 

 subject was presented with a series of numeral stimuli. These numerals 

 were presented at different rates on a screen in front of the subject. The 

 subject either pressed keys to indicate the correct number or called out 

 the name of the numeral. The bits per stimulus is a measure of the number 

 of possible numerals that can be displayed in one block of trials. The data 

 presented indicate that the complexity of the human data processing and 

 read-out system can be adequately studied to the point that system 

 specifications can be based on objective and reliable data. 



This point of view is further emphasized in the results of a study in which 

 the human operator was asked to perform as an error sensor in a tracking 

 system.' Fig. 12-32 is a block diagram of this system. In this study it was 

 necessary to determine the characteristics of the display that would lead 

 to optimum performance. An examination of the engineering and psycho- 



Function 

 Generator 



Error Plus Noise 



Input Heading 

 Command 



!//=Yaw Angle 



Scope 



Pilot 



Roll Angle 



5, =Stick 

 Deflection 



Aileron 

 Deflection 



Fig. 12-32 Block Diagram of Experimental Setup. 



8E. A.'Alluisi, P. F. Muller, Jr., and P. M. Fitts, Rate of Handling Information and the Rate 

 of Information Presentation, WADC Technical Note 55-745, December 1955. 



9A. Kahn and M. Mazina, Human Tracking Performance I. Tracking Ability as a Function 

 of System Noise, Scope Sensitivity and Forcing Function, Westinghouse Electric Corp., System 

 Research and Development Rpt. 57-103-6-1 16- A- 1, March 1957. 



