Inhibition of Return in Three-Dimensional Space is Modulated by Depth and Object Membership

We conducted a cued target localization experiment to examine inhibition of return (IOR) in a computer-simulated three-dimensional (3D) environment. Cues and targets were presented either on the same or different depth planes, and on the same or opposite sides. In trials where cues and targets were at different depths, they were positioned either within a single object extending across depth or across two distinct objects separated along the depth axis. IOR was reduced when the cue appeared farther than the subsequent target (a far-to-near switch), compared to when both appeared at the same depth. Notably, this depth-specific reduction in IOR only emerged when the cue and target appeared between different objects, not when they were part of the same object. By contrast, no such effect was found for near-to-far depth switches. These findings suggest that IOR can be modulated by both depth and object structure, but only under specific spatial configurations-particularly when attention shifts from a farther to a nearer location across separate objects.