Figure 3. Luminance manipulation experiments.

Luminance attenuates working memory and imagery, but only for good imagers. (A). The graph shows the mean performance for all participants in the luminance and no luminance conditions. There is no significant effect of luminance. Error bars show ± SEMs (N = 17). (B). Data separated by imagery ability using a median split. The leftmost graph shows the data for poor imagers (N = 10), graph on the right for good imagers (N = 7), error bars show ± SEM. Good imagers show an effect of background luminance. It should be noted that separating participants by imagery ability using a mean split resulted in the same patterns with no differences in performance for poor imagers and attenuation effects for good imagers when in the luminance condition for visual working memory and luminance respectively, t(5) =  −6.19, p = .002, and t(5) =  −4.21 p = .008.