Vivid mental imagery is a strength but also has its downsides (Knauff et al., 2002). Especially patients with trauma-related disorders suffer from distressing visual memories often experienced as uncontrollable (Brewin et al., 2010). Under which conditions can people voluntarily control the vividness of their mental images? Using congruency effects between imagery and perception as an objective measure of vividness, Cochrane et al. (2021) showed that healthy humans can intentionally control how vividly they generate mental images of colored shapes. Yet, it remains unclear whether already present mental images can be voluntarily downregulated. To investigate this, we are planning a behavioral experiment adapting Cochrane et al.’s paradigm. Twenty-eight healthy adults will perform pair sequences of visual pop-out search tasks. Between the tasks, participants will be asked to vividly imagine a shape in the previous distractor color. In half of the trials, an auditory cue will then instruct them to “dim” the mental image during the interval, while in the control trials, the cue indicates to keep it up. We expect faster search times if the target color is congruent to the previously imagined color. Most importantly, we expect this effect to be smaller in “dimmed” compared to vivid-imagery trials, indicating that the vividness of the mental image can be intentionally reduced. We further expect practice effects, and that objective imagery effects align with subjective vividness ratings. Exploratorily, we will assess individual imagery control strategies. The results are meant as a pilot study for following experiments in trauma patients.