Biomedical subjects

C Craver-Lemley

Publications and source records attributed to C Craver-Lemley.

4 recordsLinked to original sources

PubMed2001

Imagery-induced interference on a visual detection task.

The literature on the interaction between visual imagery and visual perception provides conflicting outcomes. Some studies show imagery interferes with perception whereas others show facilitation on perceptual tasks. The effects of visual imagery on a detection task were examined in six experiments. When either a bar image (Experiment 1) or an image of the letter 'l' (Experiment 3) overlapped with the targets, interference was discovered; however, images not overlapping the target did not effect detection (Experiments 2 and 4). Increasing the number of target locations caused the interfering effects of the image to disappear; however, there was no evidence of facilitation (Experiment 5). Physical stimuli interfered with detection whether there was overlap or not (Experiment 6). The results indicate that imagery induced interference may be lessened with more complex visual displays.

Cognition↗

PubMed1997

Effects of imagery on vernier acuity under conditions of induced depth.

Imagery interferes with visual acuity (the "Perky effect") when an image is close to a visual target and both the image and the acuity target are located in the same depth plane. Whether imagery-induced interference occurs when a mental image and a target are separated by induced depth was investigated. Participants projects an image in front of or behind a vernier acuity target on a frontal or back plan suggested by the panels of an outline cube. A drop in accuracy for the target was found when an image was projected in front of, but not behind, the target. Thus, induced depth can influence the Perky effect. By contrast, real lines interfered with the target regardless of perceived depth plane, which is inconsistent with the hypothesis that imagery and perception are equivalent. Results support the hypothesis that images interfere with perception only when the participant must see through an image to obtain information specifying the visual target.

Depth Perception↗

PubMed1992

How visual imagery interferes with vision.

Mental visual imagery interferes with vision: the Perky (1910) effect. Is the effect optical, sensory, perceptual, attentional, or just a response bias? Acuity was measured (in undergraduates and graduates) using target lines, with and without images (of lines). Optics (fixation, pupil size, accommodation), response bias, global attention (effort; diversion of attention to imagery), perceptual assimilation (target incorporation by imagery) and perceptual masking (of target by imagery) all fail to explain the effect. Foveally, local attention plays a limited role, as the Perky effect in divided attention is half that in focused attention, but this interaction vanishes with extrafoveal targets. Images produce primarily sensory interference, mimicking a reduction in target energy.

Adult↗

PubMed1987

Visual imagery selectively reduces vernier acuity.

Mental imagery interferes with perception. This, an example of the 'Perky effect', was studied for vernier acuity. Mean accuracy for reporting the offset of vertical line targets declined from 80% to 65% when subjects were requested to imagine vertical lines near fixation. Images of horizontal lines or of a grey mist in the fixation region lowered accuracy to a similar extent. However, accuracy was barely affected when the image was requested 1.5 deg or more from the target. The Perky effect remained strong for at least 4 s after an instruction to 'clear' the image away. The results were not due to imagery-induced changes in fixation, pupil diameter, or accommodation, or (at least primarily) to central attentional or decisional factors. Rather, imagery produces a local, pattern-insensitive, and relatively long-lasting reduction in visual sensitivity. The sensitivity loss may be mimicked by a 0.24 log unit reduction in target energy.

Fixation, Ocular↗