One of the key challenges in the field of haptic research is designing plausible stimuli using haptic interfaces with limited degrees of freedom. Although the plausible approach, which simplifies and/or exaggerates stimuli to enhance information transfer or create an artistic effect, has proven effective, evaluations of such stimuli have traditionally relied on subjective measures. This study aims to establish an objective evaluation method for haptic stimuli designed using the plausible approach. Focusing on stiffness/material perception, we developed a Stroop test within visuo-tactile tapping interactions in a virtual space. The demonstration system presents visual (textures) and tactile (vibration) stimuli at the moment of contact between a stylus and a cube, prompting participants to immediately identify the material they perceive visually. If the tactile stimuli are perceived as plausible, reaction times will be longer when the visual and tactile stimuli represent different materials than when they represent the same material.