knee-jerk reaction. Fig. an automatic or reflex reaction; an immediate reaction made without examining causes or facts. With one of his typical knee-jerk reactions, he said no immediately, citing some moral argument that no one understood. See also: reaction.
What did you see when the patients head was rolled to the opposite side? In horizontal canal BPPV, you should have seen a direction change. When the horizontal nystagmus is geotropic, the BPPV is suspected to be canalithiasis, occurring on the side with the more intense nystagmus.
In the following set of axes, the vertical scale is logarithmic (equal scale between powers of 10) and the horizontal scale is linear (even spaces between numbers). There are no negative numbers on the y-axis, since we can only find the logarithm of positive numbers. Semilogarithmic axes.