Σ Sphragis

Benchmark results

Sphragis

19 models · 8 baselines and floors

Select a row to highlight its line in the plot; rows with diagnostics also compare accuracy by author

Sentence. Main in-work track, 28 authors. The test split holds out random sentences of every work; the same works appear in training. Athenaeus is a compilation of quotation and is retained on this track only.

  • Representation:
  • Combination selected before test
  • GreBERTa
  • KainoBERTa
  • KainoBERT
  • LUAR encoder
  • Qwen3.5
  • Char n-gram
  • Lemma TF-IDF
  • Function words
  • Cosine Delta
  • Syntax (human trees)
  • Syntax (machine trees)
  • Syntax
  • Burrows
  • ALM
  • Metrical line
  • Stacked ensemble
  • Floor (no Greek seen)
Sentence
Markup-only (machine trees)floorscikit-learn logistic regression19.934.133.1sentence 82 / 82 / 82; work-held-out 80 / 80 / 80; tragedians 79 / 79 / 79; orators 78 / 78 / 78; historians 79 / 79 / 79; archaic epic 78 / 78 / 78; tragedians (works held out) 78 / 78 / 78; orators (works held out) 78 / 78 / 78Floor: non-lexical rates over UPOS, DEPREL and FEATS values, head direction, binned head distance and function words heading anything, plus token count of the machine annotation and no Greek at all; a model that does not clearly beat it has demonstrated annotation-scheme identification, not authorship attribution. From the dataset's metadata/leakage_report_conllu_machine.json
Markup-only (human trees)floorscikit-learn logistic regression17.733.031.1sentence 70 / 70 / 70; work-held-out 69 / 69 / 69; tragedians 65 / 65 / 65; orators 66 / 66 / 66; historians 67 / 67 / 67; archaic epic 64 / 64 / 64; tragedians (works held out) 64 / 64 / 64; orators (works held out) 64 / 64 / 64Floor: non-lexical rates over UPOS, DEPREL and FEATS values, head direction, binned head distance and function words heading anything, plus token count of the human annotation and no Greek at all; a model that does not clearly beat it has demonstrated annotation-scheme identification, not authorship attribution. From the dataset's metadata/leakage_report.json

Scores are held-out test macro-F1 (%) with a 95% bootstrap interval under each, over test rows on the in-work tracks and over held-out works on the work-held-out tracks; the bold value is a column's best only when its interval lies wholly above every other contender's, so a column may have no bold value. On the work-held-out tracks the score is over the authors with a same-genre rival; the singletons' figure beside it is a genre floor. Grey floor rows see no Greek (majority class, markup-only probes), or are contenders the third edition publishes as floors (the human-tree syntax rates, the function-word Cosine Delta), pinned at the bottom. The pre-committed pick row is the one combination chosen per task before its test score was read, and the only combination whose test score exists; hover one of its cells for that task's recipe, or select the row for the full list.

Plotted results

Score by task size

Held-out test macro-F1 (%); points are linearly connected. Select a line, a table row, or a legend entry to highlight one model.

0.820.640.560.380.2100Macro-F1 (%)1 sentence5 sentences10 sentencesChar n-gram: 1 sentence, 65.77%Char n-gram: 5 sentences, 95.50%Char n-gram: 10 sentences, 97.45%GreBERTa (end-to-end): 1 sentence, 71.59%GreBERTa (end-to-end): 5 sentences, 95.26%GreBERTa (end-to-end): 10 sentences, 97.37%KainoBERT (end-to-end): 1 sentence, 65.89%KainoBERT (end-to-end): 5 sentences, 92.24%KainoBERT (end-to-end): 10 sentences, 96.23%KainoBERTa (end-to-end): 1 sentence, 63.56%KainoBERTa (end-to-end): 5 sentences, 92.15%KainoBERTa (end-to-end): 10 sentences, 96.64%KainoBERT (trained on chunks): 1 sentence, 64.15%KainoBERT (trained on chunks): 5 sentences, 92.26%KainoBERT (trained on chunks): 10 sentences, 95.97%GreBERTa: 1 sentence, 64.74%GreBERTa: 5 sentences, 91.42%GreBERTa: 10 sentences, 95.52%KainoBERT: 1 sentence, 59.16%KainoBERT: 5 sentences, 90.24%KainoBERT: 10 sentences, 95.67%KainoBERTa: 1 sentence, 57.34%KainoBERTa: 5 sentences, 88.54%KainoBERTa: 10 sentences, 95.18%Lemma TF-IDF: 1 sentence, 62.92%Lemma TF-IDF: 5 sentences, 94.27%Lemma TF-IDF: 10 sentences, 98.48%Burrows lemma z-scores: 1 sentence, 42.49%Burrows lemma z-scores: 5 sentences, 84.28%Burrows lemma z-scores: 10 sentences, 94.23%Cosine Delta (lemma frequencies): 1 sentence, 40.35%Cosine Delta (lemma frequencies): 5 sentences, 80.41%Cosine Delta (lemma frequencies): 10 sentences, 92.30%Cosine Delta (function words only): 1 sentence, 18.04%Cosine Delta (function words only): 5 sentences, 43.28%Cosine Delta (function words only): 10 sentences, 61.19%Syntax feature rates (human trees): 1 sentence, 40.64%Syntax feature rates (human trees): 5 sentences, 76.62%Syntax feature rates (human trees): 10 sentences, 86.08%Syntax feature rates (machine trees): 1 sentence, 37.06%Syntax feature rates (machine trees): 5 sentences, 75.30%Syntax feature rates (machine trees): 10 sentences, 86.67%Siamese GreBERTa (SupCon + CE): 1 sentence, 74.15%Siamese GreBERTa (SupCon + CE): 5 sentences, 95.20%Siamese GreBERTa (SupCon + CE): 10 sentences, 99.14%Siamese KainoBERT (SupCon + CE): 1 sentence, 63.53%Siamese KainoBERT (SupCon + CE): 5 sentences, 84.90%Siamese KainoBERT (SupCon + CE): 10 sentences, 87.92%LUAR-style encoder + kNN: 1 sentence, 47.89%LUAR-style encoder + kNN: 5 sentences, 69.42%LUAR-style encoder + kNN: 10 sentences, 72.55%LUAR-style encoder + linear probe: 1 sentence, 56.60%LUAR-style encoder + linear probe: 5 sentences, 79.89%LUAR-style encoder + linear probe: 10 sentences, 85.61%Char n-gram Dirichlet-multinomial: 1 sentence, 67.15%Char n-gram Dirichlet-multinomial: 5 sentences, 94.34%Char n-gram Dirichlet-multinomial: 10 sentences, 96.97%Char n-gram naive Bayes: 1 sentence, 67.01%Char n-gram naive Bayes: 5 sentences, 94.29%Char n-gram naive Bayes: 10 sentences, 97.07%OLMo-1B authorial language models: 1 sentence, 62.97%OLMo-1B authorial language models: 5 sentences, 83.26%OLMo-1B authorial language models: 10 sentences, 83.51%Qwen3.5-27B (LoRA, tuned on train): 1 sentence, 72.49%Qwen3.5-27B (LoRA, tuned on train): 5 sentences, 96.96%Qwen3.5-27B (LoRA, tuned on train): 10 sentences, 98.69%Qwen3.5-27B (zero-shot): 1 sentence, 26.12%Qwen3.5-27B (zero-shot): 5 sentences, 49.26%Qwen3.5-27B (zero-shot): 10 sentences, 58.74%Combination selected before test: 1 sentence, 74.43%Combination selected before test: 5 sentences, 96.72%Combination selected before test: 10 sentences, 98.39%Majority class: 1 sentence, 0.79%Majority class: 5 sentences, 0.79%Majority class: 10 sentences, 0.79%Markup-only (human trees): 1 sentence, 17.67%Markup-only (human trees): 5 sentences, 33.00%Markup-only (human trees): 10 sentences, 31.11%Markup-only (machine trees): 1 sentence, 19.90%Markup-only (machine trees): 5 sentences, 34.08%Markup-only (machine trees): 10 sentences, 33.09%

Has the encoder seen the test sentences?

EncoderPretraining corpusBenchmark testBenchmark trainCorpus seenCorpus unseenSeen − unseenTest position on seen scale
grebertanot this corpus (AncientGreek-no-sphragis-v1 used as reference text)46.145.746.843.23.6n/a
kainobertAncientGreek-no-sphragis-v232.932.038.038.8-0.87.61
kainobertaAncientGreek-no-sphragis-v212.812.216.819.1-2.42.69

Top-1 masked-token accuracy (%). A clean encoder scores the benchmark test sentences at its unseen level. KainoBERT is pretrained from the second corpus derivative, which removes the benchmark's works and passages, and sits below its unseen level. The first KainoBERT, pretrained from a derivative that removed exact lines only, scored the test sentences at its seen level (0.460 against 0.434 unseen and 0.463 seen) and was withdrawn on 2026-09-24. GreBERTa was pretrained elsewhere on corpora not screened for the benchmark and is shown as a baseline only.