SOMtime the World Ain$'$t Fair: Violating Fairness Using Self-Organizing Maps
This reveals a fairness risk in unsupervised machine learning pipelines, indicating that fairness through unawareness fails for ordinal sensitive attributes, which is a problem for practitioners auditing AI systems.
The paper tackled the assumption that unsupervised representations are neutral to sensitive attributes by showing that Self-Organizing Maps (SOMtime) can recover such attributes as latent axes, achieving Spearman correlations up to 0.85 on real-world datasets, while other methods like PCA and UMAP remained below 0.23.
Unsupervised representations are widely assumed to be neutral with respect to sensitive attributes when those attributes are withheld from training. We show that this assumption is false. Using SOMtime, a topology-preserving representation method based on high-capacity Self-Organizing Maps, we demonstrate that sensitive attributes such as age and income emerge as dominant latent axes in purely unsupervised embeddings, even when explicitly excluded from the input. On two large-scale real-world datasets (the World Values Survey across five countries and the Census-Income dataset), SOMtime recovers monotonic orderings aligned with withheld sensitive attributes, achieving Spearman correlations of up to 0.85, whereas PCA and UMAP typically remain below 0.23 (with a single exception reaching 0.31), and against t-SNE and autoencoders which achieve at most 0.34. Furthermore, unsupervised segmentation of SOMtime embeddings produces demographically skewed clusters, demonstrating downstream fairness risks without any supervised task. These findings establish that \textit{fairness through unawareness} fails at the representation level for ordinal sensitive attributes and that fairness auditing must extend to unsupervised components of machine learning pipelines. We have made the code available at~ https://github.com/JosephBingham/SOMtime