**Ding, Y., Hults, C.M., Raja, R., & Simons, D. J. (2023). Similarity of an unexpected object to the attended and ignored objects affects noticing in a sustained inattentional blindness task. *Attention, Perception, & Psychophysics*, *85*, 2150–2169. https://doi-org.proxy2.library.illinois.edu/10.3758/s13414-023-02794-2** Studies of inattentional blindness reliably find greater noticing for unexpected objects that are similar to the attended objects and less noticing for those that are similar to the ignored objects. Other studies show that noticing rates are lower when the primary task is more difficult. To our knowledge, no studies have examined, systematically, how varying the similarity of the attended and ignored items to each other affects noticing of an unexpected object that differs from both. This planned set of studies will examine whether people notice unexpected objects more or less when the attended and ignored objects vary in their similarity to each other.