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

Abstract

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.

Temporal integration between visual images and visual percepts.

“…For example, in one of the earliest demonstrations of image-percept interaction, Perky (1910) showed that while intentionally imagining an object, subjects were less able to detect a brief visual presentation of that object as compared with cases where imagery was absent (see also Neisser, 1976;Posner, Boies, Eichelman, & Taylor, 1969). More modern replications of the Perky effect have repeatedly shown that visual detection (e.g., Segal, 1971;Segal & Fusella, 1970) and discrimination (e.g., Craver-Lemley & Reeves, 1992; Craver-Lemley, Arterberry, & Reeves, 1997;Reeves, 1981) are impaired by visual imagery (see also Craver-Lemley, Arterberry, & Reeves, 1999). However, imagining a visual scene facilitates object recognition for items that are semantically related to the imagined scene (Peterson & Graham, 1974), and an imagined context also aids in making judgments about visual patterns (Freyd & Finke, 1984).…”

Imagery-induced interference on a visual detection task

“…Although Craver-Lemley and her colleagues (see Craver-Lemley and Reeves, 1992;Craver-Lemley et al, 1997) have provided evidence ruling out an effort explanation in their studies, this explanation needs to be addressed because the method used in Experiment 1 differed from the methods previously used. To test this possibilit y, participants were asked to evoke a horizontal bar image that lled three of the cells horizontally.…”

“…Therefore, under the imagery condition, the image overlapped the asterisk target. A bar image was used because it has been demonstrated to produce both a Perky effect (Craver-Lemley et al, 1997) and facilitation (Finke, 1986). Furthermore, lling cells with an image was similar to Farah' s (1985Farah' s ( , 1989 method for projecting letter images.…”

“…Some report that imagery can interact with physical percepts to improve or facilitate perceptual tasks (Freyd and Finke, 1984;Farah, 1985Farah, , 1989Sagi, 1995, 1997a; see Kosslyn, 1994 for review); while others have discovered that performance is hindered under imagery (Perky, 1910;Segal and Fusella, 1970;Reeves, 1981;Craver-Lemley and Reeves, 1987;Craver-Lemley et al, 1997;Ishai and Sagi, 1997b; see Craver-Lemley and Reeves, 1992 for review).…”

“…For instance, Baddeley et al (1975) found that visual imagery interfered with visual tracking performance, and Finke (1986) reported that visual imagery reduced detection of a visual target presented under dif cult viewing conditions. Craver-Lemley and her colleagues (Craver-Lemley and Reeves, 1987Reeves, , 1992Craver-Lemley et al, 1997) have systematically investigated the effects of visual imagery on vernier acuity. A Perky effect was discovered when participants were asked to imagine a stimulus in the same spatial region in which a vernier acuity target was rapidly presented.…”