MEASURING PERFORMANCE EFFICIENCY AND CONSISTENCY IN VISUAL DISCRIMINATIONS WITH NOISY IMAGES

These experiments measured the efficiency of disk discrimination perfo rmance, relative to an ''ideal'' observer, and compared 2 visually dis similar tasks in which noisy image stimuli were identical for a physic al calculation yielding optimum decisions. Performance consistency was measured by estimating the assumed underlying correlation in an obser ver's judgments about the same individual ''frozen noise'' images acro ss independent replications of each condition. Larger disk sizes on th e stimulus images considerably reduced observer performance efficiency (by a factor of 10) in both discrimination tasks, regardless of the i mage viewing distance. But even when efficiency was very low (5% or le ss), performance consistency still remained quite high (about 50%). Ab out half of each observer's inefficiency appeared to reflect consisten t (but suboptimal) perceptual ''miscalculations'' of the noisy stimulu s information.