the minimum amount of stimulation required to trigger a reaction or produce a sensation. Absolute threshold is measured across several trials. It is the lowest or weakest level of stimulation (e.g., the slightest, most indistinct sound) that can be detected on 50% of trials. Although the name suggests a fixed level at which stimuli effectively elicit sensations, the absolute threshold fluctuates according to alterations in receptors and environmental conditions. Also called absolute limen (AL); detection threshold; sensation threshold.