Imagery-induced light and dark adaptations

Abstract

The present study examines whether mental imagery could induce light and dark adaptations. The participants discriminated differences in brightness between an achromatic standard stimulus and multiple comparison stimuli under a control condition in the first experiment. In imagery conditions, the participants performed the same task with images generated based on previously presented achromatic cues; one was darker than the standard stimulus, while another was brighter. With the generated darker image, the participants could discriminate smaller differences in brightness than under the control condition. However, the participants needed greater differences in order to be able to discriminate between the standard stimulus and multiple comparison stimuli with the generated brighter images. The second experiment indicates that observing a cue stimulus without an intention to create a mental image does not induce such effects. These results suggest that darker and brighter images induced dark and light adaptations, respectively. In the first experiment, the participants observed the cue stimuli with one eye and performed the discrimination task with the other eye. The procedure suggests that imagery induced adaptation is not at the peripheral level (e.g., the retina), but at the central level of visual processing.