In certain experiments, an image is briefly shown and immediately followed by a masking stimulus that prevents the conscious awareness of the initial image. What phenomenon are the researchers investigating in these studies?

Explanation

Option A refers to tinnitus, a hearing condition unrelated to visual masking. Option B describes accommodation, the eye's focusing mechanism. Option C, blindsight, involves visual processing without conscious sight but is distinct from masking. Option D, priming, correctly describes how a stimulus can affect response even when not consciously perceived, which is the focus of these experiments.