threshold

(thresh’dld). That degree of stimulus that just produces a sensation; a stimulus that is just appreciable or just comes within the limits of perception. Called also Schwelle. absolute t., the lowest po ible limit of perceptibility of any sensation. Called also stimulus (. achromatic t., the least intensity of the spectrum that produces a sensation of color. Reduction of intensity below this point produces a sensation of brightne only, without any color distinction. auditory t., the mini’mum audib’ile, or slightest perceptible sound. t. of consciousne , the mini’ mum sensib'ile, or lowest limit of sensibility. differential t., the lowest limit of discriminative sensibility; the ratio which the difference of two stimuli must bear to half their sum in order that their difference may be just perceptible. double-point t., the smallest distance apart at which two stimuli of touch are felt as distinct. meuron t., that degree of excitation of a neuron which just suffices to call forth a fruitful excitation (sensation, movement, or the like) in a neuron with which it is in contact. relational t., the ratio which two stimuli must have to each other in order that the difference between them may be just t perceptible. stimulus t. See absolute (. isual sensation, the mini’mum vis’ ible, ot " slightest po ible vision of any object.