relational threshold

re·la·tion·al thresh·old

the smallest degree of difference between two stimuli that permits them to be perceived as different.
Farlex Partner Medical Dictionary © Farlex 2012

re·la·tion·al thresh·old

(rĕ-lāshŭn-ăl threshōld)
Smallest degree of difference between two stimuli that permits them to be perceived as different.
Medical Dictionary for the Dental Professions © Farlex 2012