Constructive feedback is crucial for creative writers to refine their storytelling abilities. Since receiving feedback from human experts is often costly and time-intensive, large language models (LLMs) offer a scalable and efficient alternative as automatic writing assistants. Despite their potential, research indicates that LLM-generated feedback is often generic, lacks actionability, and fails to identify which writing issue is most critical. To address these limitations, we present a reinforcement learning approach that steers LLMs to generate constructive feedback without the need for ground-truth feedback. We train our model using group relative policy optimization (GRPO) with a novel multi-component reward function aiming at constructiveness: it prioritizes feedback that is uniquely tailored to the story, helps to improve story quality, and addresses the most critical writing issue. In automatic and human evaluation across three story corpora, our approach outperforms state-of-the-art LLMs (including Gemini) and competitive baselines. We find that providing actionable suggestions is the main driver of feedback constructiveness.
Figures & tables
Figure 1: Example story from Rashkin et al. (2025) with two generated feedback texts, highlighting the criteria of constructiveness our approach improves compared to standard LLM prompting: (a) priority in addressing the most critical issue, (b) specificity to the given story, and (c) actionability via concrete revision instructions.
Figure 2: Our reinforcement learning approach to story feedback generation, including the policy π(f∣s) for generating feedback f on a story s , and the multi-component reward function R(s,f) based on scoring models for priority, specificity, and actionability.
Model
Priority
Specificity
Actionability
mse ↓
pcc ↑
mse ↓
pcc ↑
mse ↓
pcc ↑
Random baseline
.197
.100
.332
-.096
.213
.008
Mean baseline
.128
.075
.120
.036
.100
.031
Reward model
.092
.537
.031
.865
.058
.651
Table 1: Reward model performance measured by mean squared error ( mse ) and Pearson correlation coefficient ( pcc ) for priority , specificity , and actionability .
Model
Approach
(a) StoryFeedback
(b) Storal
(c) WritingPrompts
Pr
Sp
Ac
Avg
Rank ↓
Pr
Sp
Ac
Avg
Rank ↓
Pr
Sp
Ac
Avg
Rank ↓
Gemma
Base targeted
.718
.912
.763
.798
9.41
.688
.862
.727
.759
10.46
.734
.919
.757
.803
8.19
GRPO targeted
.952
.993
.930
.958
7.33 ‡
.874
.987
.860
.907
5.89 ‡
.907
.974
.875
.919
4.32 ‡
Base open
.668
.971
.780
.807
4.93
.655
.951
.733
.780
5.26
.685
.949
.758
.797
4.28
GRPO open
.930
.998
.914
.947
4.76
.825
.984
.823
.877
4.72
.845
.979
.857
.894
2.96 ‡
LLaMA
Base targeted
.803
.966
.790
.853
8.02
.753
.962
.764
.827
7.74
.790
.954
.772
.839
8.59
Table 2: Automatic evaluation results of feedback generation on (a) StoryFeedback, (b) Storal, and (c) WritingPrompts: Mean priority ( pr ), specificity ( sp ), actionability ( ac ), their average ( avg ), and the Bradley-Terry average rank computed from pairwise multi-LLM judgments (see Section 5.4 ) for our approach GRPO , the three instruction-tuned Base LLMs, and Gemini using targeted and open prompts. Bold: best overall; underlined: best per model family; ‡ : significant rank improvement over the Base counterpart (Wilcoxon signed-rank test, p<.05 ).
Approach
(a) StoryFeedback
(b) Storal
(c) WritingPrompts
Pr
Sp
Ac
Avg
Rank ↓
Pr
Sp
Ac
Avg
Rank ↓
Pr
Sp
Ac
Avg
Rank ↓
Base open
.668
.971
.780
.807
4.53
.655
.951
.733
.780
5.86
.685
.949
.758
.797
5.00
GRPO open_pr
.969
.998
.901
.956
5.94
.910
.984
.834
.909
5.47
.930
.963
.837
.910
6.48
GRPO open_sp
.724
.991
.808
.841
4.18
.692
.982
.753
.809
4.01
.709
.976
.789
.825
4.26
GRPO open_ac
.884
.988
.950
.941
3.08
.786
.984
.860
.877
2.15
.817
.979
.882
.893
3.10
GRPO open_no_pr
.842
.996
.896
.911
4.33
.753
.983
.819
.852
3.32
.761
.979
.835
.858
3.37
Table 3: Ablation study of reward signals in feedback generation using the Gemma model. We compare our full approach GRPO open against variants trained with a single reward signal ( open_pr / open_sp / open_ac ), and all but one reward signal ( open_no_pr / open_no_sp / open_no_ac ). Metrics as in Table 2 .
Figure 3: Comparison of model performance on human-written stories ( original rank ) versus synthetically-corrupted stories from the StoryFeedback corpus ( corrupted rank ). The dotted lines show the balanced rank .
Approach
Pr
Sp
Ac
Co
Gemma+Base open
4.23
4.81
3.70
3.55
Gemma+GRPO open
4.24
4.85
3.96
3.69 ‡
Gemma+GRPO open_ac
4.45
4.90
4.11
4.01 ‡
Gemini+Base open
3.61
4.40
3.59
3.19
Table 4: Human evaluation of feedback in terms of priority ( pr ), specificity ( sp ), actionability ( ac ), and constructiveness ( co ). Our approach Gemma+GRPO open_ac is best in all dimensions (bold), followed by the full approach Gemma+GRPO open (underlined). Both are significantly better ( ‡ ) than Gemma+Base open (Wilcoxon signed-rank test with Bonferroni correction, p<.05 ).
Criterium
Pr
Sp
Ac
Co
Priority (Pr)
0.313
0.246
0.452
Specificity (Sp)
0.313
0.214
0.226
Actionability (Ac)
0.246
0.214
0.556
Constructiveness (Co)
0.452
0.226
0.556
Table 5: Kendall’s τ correlation between the feedback criteria rated in the human evaluation. The highest value per colunm is marked in bold.
Appendix figures & tables6 assets
Supplementary material from the paper’s appendix.
Appendix
Hyperparameter
Value
Optimizer
Paged AdamW 8-bit
Learning Rate
5×10−6
Learning Rate Scheduler
Cosine
Warmup Ratio
0.03
Weight Decay
0.01
GRPO Group Size ( G )
8
Appendix
Table 6: Hyperparameters used for GRPO training.
Judge Model
Gemma (9B)
LLaMA (8B)
Qwen (7B)
Gemma (27B)
3.80 %
-5.07%
1.26%
LLaMA (72B)
-4.15%
2.63 %
1.52%
Qwen (72B)
0.35%
2.43%
-2.78 %
Appendix
Table 7: Relative preference matrix: Bold diagonal elements indicate the self-preference delta ( Δself ), representing the deviation in win rate when a judge evaluates its own model family compared to the cross-family average. Positive values denote a relative preference, while negative values indicate a relative aversion.
Model
Approach
(a) Original Stories
(b) Corrupted Stories
(c) All Stories
Pr
Sp
Ac
Avg
Rank ↓
Pr
Sp
Ac
Avg
Rank ↓
Pr
Sp
Ac
Avg
Rank ↓
Gemma
Base targeted
.672
.857
.740
.757
9.98
.733
.931
.771
.812
9.23
.718
.912
.763
.798
9.42
GRPO targeted
.938
.995
.922
.952
7.68
.954
.994
.927
.959
7.21
.950
.995
.926
.958
7.33
Base open
.648
.966
.770
.795
2.90
.675
.973
.783
.810
5.61
.668
.971
.780
.807
4.93
GRPO open
.918
.997
.908
.941
2.86
.934
.998
.916
.949
5.39
.930
.998
.914
.947
4.76
LLaMA
Base targeted
.787
.976
.782
.848
8.26
.809
.963
.793
.855
7.94
.803
.966
.790
.853
8.02
Appendix
Table 8: Automatic feedback generation results on (a) original, (b) corrupted (backtranslated, sentence swapped, sentence deleted), and (c) all stories from the StoryFeedback corpus. We compare our approach GRPO against instruction-tuned Base LLMs and Gemini using targeted and open setups: Mean priority ( pr ), specificity ( sp ), and actionability ( ac ) scores and the Bradley-Terry average rank computed from pairwise multi-LLM judgments (see Section 5.4 ). Underlining marks the best value per model family; bold marks the best overall.
Human \ Reward
Pr
Sp
Ac
Co
Priority (Pr)
.35
.30
.29
.31
Specificity (Sp)
.37
.53
.38
.47
Actionability (Ac)
.29
.32
.42
.34
Constructiveness (Co)
.34
.28
.30
.43
Appendix
Table 9: Pearson correlation between reward model predictions (columns) and human ratings from the manual evaluation (rows). Bold marks each reward component’s correlation with its matching human dimension.
Human \ Judge
Llama
Gemma
Qwen
Majority
Priority (Pr)
.32
.32
.31
.34
Specificity (Sp)
.37
.36
.33
.38
Actionability (Ac)
.22
.21
.20
.23
Constructiveness (Co)
.36
.35
.34
.38
Appendix
Table 10: Pearson correlation between LLM judge verdicts (columns) and human ratings from the manual evaluation (rows). The majority-vote ensemble correlates most strongly with human judgments in every dimension (bold).
Judge \ Reward
Pr
Sp
Ac
Co
Llama 72B
.28
.43
.33
.37
Gemma 27B
.34
.45
.35
.42
Qwen 72B
.15
.35
.25
.27
Majority
.27
.43
.33
.37
Appendix
Table 11: Pearson correlation between reward model predictions (columns) and LLM judge verdicts (rows).
While LLMs hold significant potential to transform scientific research, we advocate for their use to augment and empower researchers rather than to automate research without human oversight. To this end, we study constructive feedback generation, the task of producing targeted, actionable feedback that helps authors improve both their research and its presentation. In this work, we operationalize the effectiveness of feedback along two author-centric axes-validity and author action. We first curate GoodPoint-ICLR, a dataset of 19K ICLR papers with reviewer feedback annotated along both dimensions using author responses. Building on this, we introduce GoodPoint, a training recipe that leverages success signals from author responses through fine-tuning on valid and actionable feedback, together with preference optimization on both real and synthetic preference pairs. Our evaluation on a benchmark of 1.2K ICLR papers shows that a GoodPoint-trained Qwen3-8B improves the predicted success rate by 83.7% over the base model and sets a new state-of-the-art among LLMs of similar size in feedback matching on a golden human feedback set, even surpassing Gemini-3-flash in precision. We further validate these findings through an expert human study, demonstrating that GoodPoint consistently delivers higher practical value as perceived by authors.
Jimin Mun, Chani Jung, Xuhui Zhou +2
Carnegie Mellon University · Independent Researcher · NVIDIA
Training models for open-ended writing requires diverse prompts and sufficiently precise specifications of response quality. Constructing such specifications at scale entails recovering task requirements, consolidating overlapping criteria, and defining observable differences between performance levels. We introduce Writer-R1, a writing training pipeline built around Inductive Rubric Generation (IRG), which integrates these operations into an automated rubric construction procedure. The pipeline expands an open writing corpus and uses the resulting prompt-specific rubrics throughout supervised training and reinforcement learning (RL). Each rubric is concatenated with the user request and also defines the reward criteria, making the requirements used for assessment available to the writer before generation. A compact model, RubricGen-4B, learns to supply rubrics for new requests. Writer-R1 improves WritingBench scores by 0.182 and 0.158 over the 4B and 8B backbones, respectively, with gains also on HelloBench. Training ablations favor IRG over direct rubric generation, and further analyses support rubric transfer and the robustness of writer improvements across evaluators. These results support using inductively mined rubrics as both generation guidance and reward specifications for open-ended writing.
Jihao Zhao, Shuaishuai Zu, Zhiyuan Ji +2
School of Information, Renmin University of China, Beijing, China · School of Information, BRAIN, Renmin University of China, Beijing, China
We investigate whether state-of-the-art large language models (LLMs) generate feedback that reflects the pedagogical practices of expert teachers in terms of feedback focus and adaptivity. Previous evaluation efforts have examined feedback characteristics, its impact on learning, and its target, yet the focus of feedback and its adaptivity remains largely overlooked. To bridge this gap, we adopt and refine Narciss's taxonomy into seven feedback focus types to annotate teacher and LLM-generated feedback across three university writing courses. We release FeedType, a benchmark containing annotated teacher and LLM feedback from six LLMs under three prompting strategies. We assess the coverage and distribution of feedback focus types, and examine whether LLMs adapt their feedback across draft stages and student performance levels as an expert instructor does. Our findings show that while most LLMs cover most feedback focus types, they fail to reflect teacher feedback distributions and show varying levels of adaptivity, with none matching the teachers' adaptive behavior. We believe FeedType will support future research on pedagogical alignment in LLM feedback generation.