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retinal rod

any of various photoreceptors in the retina that respond to low light levels, as opposed to retinal cones, which require moderate to bright light for activation. In primates, which have both rods and cones, the rods are excluded from the center of the retina, the fovea centralis. All rods contain the same photopigment, rhodopsin; therefore, the rod pathways do not provide color information. The connections of the rod pathways enhance retinal sensitivity to light, but acuity is relatively poor. See also scotopic vision.

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Psychology term of the day

October 11th 2024

method of difference

method of difference

the second of the five canons of empirical science laid down by John Stuart Mill. It is meant to establish sufficient conditions for a phenomenon. For example, if under one condition, C1, an effect, E1, does not occur, and as C1 is changed to C2 the effect E1 does occur, it may be concluded that C2 is a sufficient cause of E1, and the alternative hypothesis, that C1 causes E1, can be eliminated. Thus, the effect is attributed to the “difference” between conditions C1 and C2. Also called difference canon.