The Perky effect revisited: Imagery hinders perception at high levels, but aids it at low.

Visual, although not auditory, imagery typically interferes with visual acuity: the so-called Perky effect. However, visual images can facilitate detection of visual Gabor patterns. Here we report that this discrepancy is not due so much to the class of stimuli but primarily to the level of accuracy; visual imagery interferes with acuity when performance is good but facilitates it when performance is poor.

Rapid Adaptation of Night Vision.

Apart from the well-known loss of color vision and of foveal acuity that characterizes human rod-mediated vision, it has also been thought that night vision is very slow (taking up to 40 min) to adapt to changes in light levels. Even cone-mediated, daylight, vision has been thought to take 2 min to recover from light adaptation. Here, we show that most, though not all adaptation is rapid, taking less than 0.

Role of extrinsic noise in the sensitivity of the rod pathway: rapid dark adaptation of nocturnal vision in humans.

Unlabelled: Rod-mediated 500 nm test spots were flashed in Maxwellian view at 5 deg eccentricity, both on steady 10.4 deg fields of intensities (I) from 0.00001 to 1.