LLM-as-a-Judge evaluators are increasingly used to score open-ended generation, yet a judge's correlation with human ratings on its development set may not guarantee valid measurement when outputs are closely matched and human preferences are subjective. We study this failure mode through psychological depth in short stories. Seven human readers and an LLM-judge ensemble selected on the original scalar Psychological Depth Scale dataset (ρ=0.646) evaluated 60 blinded, prompt-matched story pairs from GPT-5 vs.\ GPT-4o and DeepSeek-R1 vs.\ DeepSeek-V3. Human preferences showed no universal reasoning advantage: GPT-5 was modestly preferred over GPT-4o (60.0--62.9%), whereas DeepSeek-R1 trailed V3 (42.9%), and inter-reader agreement was near chance (Krippendorff's α=0.070), with within-reader consistency and recurring weighting patterns suggesting structured heterogeneity rather than random responding. The judge, by contrast, favored reasoning outputs in 89.0% of dimension-level comparisons and 59 of 60 pairs on aggregate PDS, uniformly across all five evaluator configurations, and its scores were associated with surface features such as sentence length and lexical diversity. These results suggest that development-set performance is insufficient evidence for deployment validity on a shifted distribution, and that point-estimate judges can obscure the heterogeneity in subjective human evaluation.
Figures & tables
Figure 1: Human preferences vary by model pairing and dimension; the LLM judge does not. (a) Human preference for the reasoning-model story with pointwise 95% GLMM intervals; the dashed line marks chance. (b) LLM-judge preference for the reasoning-model story pooled over all 60 pairs. Solid bars are reasoning wins; hatched segments credit each exact score tie 0.5 to the reasoning story; labels give the resulting even-split rate, with raw tie counts in parentheses. Aggregate PDS averages the five dimension scores and is a distinct target from the human overall-preference question.
Appendix figures & tables25 assets
Supplementary material from the paper’s appendix.
Appendix
DeepSeek-R1
GPT-5 auto
GPT-5 high
Dimension
vs. V3
vs. 4o
vs. 4o
Authenticity
47.9% [39.0, 56.4]
55.7% [47.8, 65.6]
52.1% [43.0, 61.6]
Empathy
52.9% [44.4, 62.2]
68.6% [62.7, 78.3]
69.3% [64.4, 80.1]
Engagement
39.3% [29.6, 46.6]
58.6% [50.7, 67.3]
65.0% [58.1, 74.4]
Emotion prov.
61.4% [53.6, 69.9]
70.7% [64.2, 79.3]
62.9% [55.5, 72.3]
Narr. complexity
58.6% [50.9, 67.7]
55.0% [47.0, 64.3]
52.9% [44.5, 62.5]
Appendix
Table 1: Human preference for the reasoning-model output, with pointwise 95% GLMM intervals. Rates above 50% favor the reasoning model. The 18 intervals are unadjusted for multiplicity and interpreted descriptively.
Dimension
Fleiss’ κ
Kripp. α
Raw
Authenticity
0.035
0.037
52.5%
Emotion prov.
0.080
0.082
54.1%
Empathy
0.182
0.185
59.1%
Engagement
0.059
0.061
53.3%
Narr. complexity
0.016
0.018
52.1%
Overall preference
0.035
0.038
51.9%
Appendix
Table 2: Inter-reader agreement across 60 pairs and seven readers. Raw is mean pairwise agreement.
Dimension
All
R1 vs. V3
GPT-5 auto vs. 4o
GPT-5 high vs. 4o
Authenticity
0.037
0.073
0.053
−0.015
Emotion prov.
0.082
0.035
0.147
0.072
Empathy
0.185
0.047
0.176
0.290
Engagement
0.061
0.101
0.010
0.080
Narr. complexity
0.018
0.049
−0.013
0.005
Overall preference
0.038
0.074
−0.003
0.050
Appendix
Table 3: Krippendorff’s α by model pairing.
Figure 2: Exploratory reader-level structure. Left: coefficients from separate logistic regressions relating PDS dimensions to each reader’s overall preference. Right: within-reader Cohen’s κ between each dimension and overall preference. Similar clusters across analyses are consistent with recurring dimension-weighting patterns, but the seven-reader sample precludes population-level archetype claims.
Pairing
Human overall votes
Judge agg. PDS
Δ
dz
GPT-5 auto vs. 4o
84/140 (60.0%)
20/20
+0.518
1.14
GPT-5 high vs. 4o
88/140 (62.9%)
20/20
+0.500
1.12
DeepSeek-R1 vs. V3
60/140 (42.9%)
19/20
+0.214
0.68
Overall
232/420 (55.2%)
59/60
+0.411
0.95
Appendix
Table 4: Human overall-preference votes and judge aggregate-PDS pair decisions favoring reasoning-model outputs. These columns measure different targets and are not direct agreement statistics. Δ is the descriptive mean paired judge-score difference (reasoning minus comparison) pooled across the five routed dimensions, and dz is the corresponding standardized mean difference. Because dimensions from the same pair are dependent, we do not report naive paired-test inference.
Evaluator
AUT
PROV
EMP
ENG
NCOM
Mean/routed ρ
Llama 3.1 70B, 7 demo
0.576
0.674
0.637
0.507
0.637
0.606
Llama 3.1 70B, 5 demo
0.588
0.655
0.596
0.450
0.575
0.573
Llama 3.1 70B, 10 demo
0.561
0.702
0.671
0.387
0.568
0.578
Llama 3.3 70B, 10 demo
0.580
0.676
0.702
0.407
0.550
0.583
Qwen 3.5 397B, 7 demo
0.511
0.663
0.602
0.564
0.496
0.567
Llama 3.1 70B CoT, 10 demo
0.499
0.627
0.658
0.356
0.664
0.561
Appendix
Table 5: Spearman correlation with human PDS annotations on the 80% development/selection split. Bold marks the configuration selected for each dimension; these are not untouched-test estimates. For individual configurations, the final column is the mean of the five displayed correlations; for the routed ensemble, it is computed from routed predictions.
Configuration
Auth.
Emo.
Emp.
Eng.
Narr.
Ties
Decisive
Even-split
Llama 3.1 70B (5d)
43/44 ∗
54/57
49/54
47/51
53/55
39
94.3%
88.5%
Llama 3.1 70B (10d)
43/43
53/53 ∗
48/51
46/46
54/54
53
98.8%
90.2%
Llama 3.3 70B (10d)
32/33
53/55
51/57 ∗
47/58
47/56
41
88.8%
83.5%
Qwen 3.5 397B (7d)
57/57
58/58
55/58
57/59 ∗
57/58
10
97.9%
96.3%
Llama 3.1 70B CoT
7/8
49/50
47/53
43/55
49/59 ∗
75
86.7%
77.5%
Routed ensemble
43/44
53/53
51/57
57/59
49/59
28
93.0%
89.0%
Appendix
Table 6: Reasoning-output preference for five evaluator configurations and the routed ensemble. Dimension cells report reasoning wins / non-tied pairs; ∗ marks the routed dimension. Decisive pools wins over non-tied comparisons; Even-split credits ties 0.5 to each story over all 300 comparisons.
Dimension
Ties
Reasoning wins
Even-split rate
Authenticity
16
43
85.0%
Emotion prov.
7
53
94.2%
Empathy
3
51
87.5%
Engagement
1
57
95.8%
Narr. complexity
1
49
82.5%
Five dimensions pooled
28
253
89.0%
Appendix
Table 7: Tie frequency and reasoning-output preference for the routed ensemble. Even-split rate =(wins+0.5×ties)/60 per dimension, or /300 for the pooled row. Aggregate PDS is a separate evaluator target, not human overall preference.
Feature
Auth.
Emo.
Emp.
Eng.
Narr.
Word count
−.28
−.19
−.12
−.18
+.09
Mean sentence length
−.32
−.43
−.17
−.70
−.09
MATTR
−.37
−.33
−.35
−.29
−.14
MTLD
−.24
−.19
−.25
−.09
+.03
Appendix
Table 8: Story-level Pearson correlation between surface features and ensemble judge scores ( n=120 ).
Feature
Auth.
Emo.
Emp.
Eng.
Narr.
Word count
−.64
−.40
−.18
−.54
+.11
Mean sentence length
−.56
−.47
−.27
−.59
+.03
MATTR
−.31
−.17
−.24
−.28
+.13
MTLD
−.39
−.13
−.15
−.36
+.31
Appendix
Table 9: Within-pair standardized regression coefficients ( β ) relating surface features to ensemble judge scores ( n=60 pairs).
Model
Temperature
Other
GPT-4o
1.0 (default)
—
GPT-5 (auto)
1.0 (default)
—
GPT-5 (high)
1.0 (default)
reasoning_effort=high
DeepSeek-V3
1.0
—
DeepSeek-R1
1.0
thinking tags stripped
Appendix
Table 10: Generation parameters. All models used temperature =1.0 and default settings for top- p , frequency penalty, etc. GPT-5 (high) used OpenAI’s reasoning_effort parameter. No max-token limit was set.
ID
Premise
Sourced from r/WritingPrompts
1
While other god’s shrines are magnificent, yours is a bit too humbling. And yet a little girl visits you every year after stumbling upon it, never missing a year even as she grows old. Deeply moved, you decide to give her a parting gift greater than what any other God would dare to give.
2
Elves realized ages ago that, due to the lifespan differences between them, humans will eventually forget the reasoning for various treaties and break them. So it’s understandably shocking to the elves when they discover some long-forgotten treaties in their own records that humans never broke.
3
A princess who is going to be in an arranged marriage runs away. She cuts her hair and pretends to be a man. However, she runs into the prince who was going to get married to her. He also ran away, and he is pretending to be a woman. They instantly recognize each other.
4
"You know… Most vampires I hunted tend to see humans as just cattle." "Oh, don’t misunderstand me. This is just how I see you too." "Really? Then why don’t you hurt people in your town?" "Well, you don’t slaughter dairy cows for their meat, do you?"
5
You’re a hero with a weird name. “Anything for 20”.Yougaintheabilitytodoanything,aslongasyou’reoffered20. Everyone takes it as a joke, until one day there’s a cataclysm, and someone offers you $20 to end it.
Appendix
Table 11: All 20 premises used to prompt the models. The selection was intended to include speculative and grounded settings; 15 of 20 premises came from r/WritingPrompts. Premises from r/WritingPrompts are reproduced verbatim, including original spelling and grammatical errors.
Figure 3: Annotation interface: instructions and PDS metric definitions shown to annotators.
Figure 4: Annotation interface: side-by-side story presentation with premise shown above.
Figure 5: Annotation interface: evaluation questions and optional comment field.
Figure 6: Distribution of annotation time per pair for each of the 7 human annotators. Times exceeding 600 s are capped for display; the number of capped outliers is shown in each subplot title. Red dashed lines mark the median; navy dotted lines mark the mean of capped times. The rightmost panel compares median and mean times across annotators. Overall median annotation time is 5.2 minutes (n = 420).
Figure 7: Annotation time per pair plotted chronologically, with linear trends per annotator. Red points denote times capped at 600 s. Dashed black lines show linear trends; colored dotted lines show 5-pair rolling averages. The rightmost panel overlays all trend lines.
Figure 8: Leave-One-Annotator-Out (LOAO) stability analysis: shift in the aggregate reasoning-model win rate when each annotator is removed.
Pair
Ann
Pref.
Comment
Pair 0 (4–3 for A)
1
A
“A: greater focus on the abstract. B: prose heavy, but greater focus on concrete; convoluted”
5
A
“Story A was much more engaging because it was straightforward in depicting the stages of life…”
7
B
“Story B delves deeper into the characterization of the humble god…Death of worshiper is more profound”
Pair 24 (5–2 for A)
1
A
“A: good imagery, dialogue. B: interesting parallels, odd tone”
7
B
“A is a step by step of the prompt given. B builds up characters, establishes risk, and is authentic.”
Pair 27 (4–3 for B)
1
A
“A: like a prologue. B: prose, very nonsensical”
Appendix
Table 12: Selected annotator comments across five story pairs. Only annotators who provided free-text justifications are shown.
Figure 9: Evaluating psychological depth on a representative story pair (Pair 24, GPT-5 vs. GPT-4o). Left: human annotators displayed diverse preferences across PDS dimensions and overall preference. Right: all five evaluator configurations favored GPT-5 on every dimension. Blue denotes preference for GPT-5 and red preference for GPT-4o.
Figure 10: Preference rates for reasoning models across all 60 pairs for each of the 7 human annotators, the human average, and the ensemble LLM judge. Red denotes stronger reasoning-model preference, blue stronger base-model preference, and white 50%. Judge percentages credit each exact score tie 0.5 to the reasoning model (even-split rate; Table 7 gives tie counts). The final row compares human overall preference with the judge’s aggregate PDS, which are different targets.
Figure 11: Preference rates for DeepSeek-R1 vs. DeepSeek-V3 (20 pairs) across 7 human annotators and the GLMM group estimate.
Figure 12: Preference rates for GPT-5 (auto) vs. GPT-4o (20 pairs) across 7 human annotators and the GLMM group estimate.
Figure 13: Preference rates for GPT-5 (high) vs. GPT-4o (20 pairs) across 7 human annotators and the GLMM group estimate.
Auth.
Emo.
Emp.
Eng.
Narr.
Pref.
Reader 1
B
B
B
B
R
B
Reader 2
R
B
B
R
R
R
Reader 3
B
B
B
B
R
B
Reader 4
B
B
B
R
B
B
Reader 5
B
B
B
R
B
B
Reader 6
B
B
B
R
R
B
Appendix
Table 13: Per-reader pairwise preferences for Pair 56 (GPT-5 high vs. GPT-4o). R = prefers reasoning model, B = prefers comparison model.
Large language model (LLM)-as-a-judge research uses language models to score, compare, and verify AI outputs as scalable alternatives to human evaluation.