# When Style Similarity Scores Fail: Diagnosing Raw CSD Cosine in Artist-Style Evaluation

Source: [When Style Similarity Scores Fail: Diagnosing Raw CSD Cosine in Artist-Style Evaluation](<https://www.sota2.com/research/paper/6a02b410dbc836b87d8246ae>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2026-07-08T05:00:20.838Z

Authors: J\\"org Frochte

Published: 2026-05-09T16:15:13.000Z

## Abstract

Raw cosine in the 768-dimensional output space of the Contrastive Style Descriptor (CSD) is now widely read as an absolute, calibrated style-fidelity score for text-to-image and style-imitation evaluation. We introduce the discrimination gap, a corpus-internal, prototype-free and threshold-free diagnostic that tests whether contrastive style cosines admit an absolute same-versus-different interpretation on a candidate artist corpus. On a 1799-artwork, 91-artist public-domain corpus, raw CSD cosine yields negative point-estimate gaps for $23/91$ artists at the pairwise level ($2/91$ robust under bootstrap) and for $15/91$ in the aggregated-pool scoring regime style-fidelity evaluations typically use. CSLS readout on the frozen backbone reduces the aggregated negative-gap count to $4/91$; combined with positional-embedding interpolation to $336$ pixels it raises unsupervised pair-verification AUC from $0.883$ to $0.905$ across $25$ artist-disjoint splits. We refer to this diagnostic-driven readout protocol on the frozen backbone (CSLS as default, pos-interp $336$ as the stronger optional setting) as CSD+, not a new encoder.A cross-backbone check on CLIP-ViT-L/14, SigLIP-large and DINOv2-Large reproduces the same shared-tradition failure pattern, providing evidence that the residual reflects a shared limitation of the four backbones we tested rather than a CSD-specific artefact. Practical implication: before reporting CSD cosine as an absolute style-fidelity score, run the diagnostic on the candidate corpus; CSLS is the minimal correction when it fails.

## Recorded benchmark results

A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage.

- [Artist Verification on 91-artist corpus (25 random artist-disjoint splits)](<https://www.sota2.com/research/sota/artist-verification-on-91-artist-corpus-25-random-artist-disjoint-splits.md>): Artist Verification; 91-artist corpus (25 random artist-disjoint splits); Mean AUC: 91.7.

- [Style Verification on 91-artist corpus strict-anchor (25 artist-disjoint splits)](<https://www.sota2.com/research/sota/style-verification-on-91-artist-corpus-strict-anchor-25-artist-disjoint-splits.md>): Style Verification; 91-artist corpus strict-anchor (25 artist-disjoint splits); Wins (out of 25): 25.

## Original sources and implementation

[Original paper](<https://arxiv.org/abs/2605.09030>)

[PDF](<https://arxiv.org/pdf/2605.09030.pdf>)