Medical image production and display has reached the stage where decisions about what is in the image, and where, are limited solely by statistical noise. One would like to know how well humans use image information and what steps might be taken to improve decision performance. A number of experiments demonstrate that human decision-making for simple tasks is very close to the theoretical limit. Under best conditions, humans require about more SNR than the ideal bserver to operate at a given decision accuracy.
Arthur E. Burgess,
"Statistical Efficiency Of Perceptual Decisions", Proc. SPIE 0454, Application of Optical Instrumentation in Medicine XII, (15 June 1984); doi: 10.1117/12.939309; https://doi.org/10.1117/12.939309