The absolute threshold concept refers to the minimum intensity of a stimulus that can be detected by an individual 50% of the time. It represents the boundary between when a stimulus is too weak to be noticed and when it becomes noticeable.
Related terms
Subliminal Perception: This term refers to stimuli that are below our absolute threshold and therefore go unnoticed consciously.
Also known as just noticeable difference (JND), this term refers to the smallest amount by which two stimuli must differ in order for an individual to perceive them as different.