MAHWISH KITTUR¹, Sami Yousif²; ¹University of North Carolina at Chapel Hill, ²Ohio State University

From the gist of a narrative to the details of the visual scene, our memories are not veridical. Yet, the ways in which we misremember things are not random either. Rather, they can reveal something meaningful about the content that is represented in the first place: Essential information tends to be preserved, and incidental information tends to be lost. Careful examination of these visual memory errors can therefore reveal the underlying format of a mental representation. Here, we exploit this fact. By having observers remember and draw simple letter-like objects, we ‘reverse engineer’ the building blocks underlying their representation. Consistent with recent work, we find evidence of topological representation. In a first experiment, using strategically designed line drawings, we investigated how angular information is distorted. We found an unambiguous bias to misremember angles as closer to 90 degrees. We found a similar pattern for line lengths: All line lengths tended to be biased towards the average value. Despite these distortions, the overall topological form – consisting of the “T-junctions” and “holes” that composed the shapes – was remarkably well preserved. In fact, holes were virtually never lost, and we found that topologically relevant junctions (e.g., T-junctions) were maintained at a higher rate than visually similar but topologically irrelevant junctions (e.g., L-junctions). In other words, while the metric properties of the line drawings were robustly washed away, the overall topological structure was preserved in memory. To investigate the stability of these findings further, we repeated the angle and length experiments with children. In a sample of five to eight year olds, we found similar distortions and memory errors as we found in adults. These results provide a direct window into the shape of visuospatial representations, revealing the topological primitives underlying visual representation throughout the lifespan.