Ashna Shah¹, Sami Yousif¹; ¹University of North Carolina at Chapel Hill

Imagine different Tetris pieces. They are all made up of four blocks, yet some appear distinctly more complex than others. Why is that? One compelling idea is that the different pieces vary in the topology of their underlying skeletal structure; we know that differences in skeletal structure predict ratings of complexity and visual engagement (Sun & Firestone, 2021). But what if participants are not asked to judge the complexity of objects, but generate objects of varying complexity? Here, we had participants complete a block-building (or block-destroying!) task in which they were asked to either modify or maintain the complexity of Tetris-esque objects by altering the number of blocks in the object. We measured changes in the number of specific topological features in the skeletal structure of the objects (e.g., T-junctions, crosses, and holes). There were strikingly different patterns of block placement depending on the instructions participants were given. When asked to increase complexity, participants added more T-junctions and crosses in the objects but added fewer L-junctions and holes (compared to the maintain-complexity condition). In two additional experiments, we did the opposite: We asked participants to remove blocks to either decrease or maintain the complexity. We found the same pattern: When asked to decrease complexity, participants retained more L-junctions and holes in the objects but retained fewer T-junctions and crosses (compared to the maintain-complexity condition). The instructions in all of these tasks were minimal: Participants were given virtually no guidelines about how to alter the blocks except to increase/decrease/maintain the complexity of the objects. Yet the objects they created as a result differed dramatically in their overall structure (a fact which is immediately apparent when looking at the resulting objects). Thus, these results demonstrate that topological structure influences not only how people perceive complexity, but also how they create complexity.