This paper presents a reproduction study aimed at reproducing and validating a human NLP evaluation performed for the DExperts text generation method. The original study introduces DExperts, a controlled text generation method, evaluated using non-toxic prompts from the RealToxicityPrompts dataset. Our reproduction study aims to reproduce the human evaluation of the continuations generated by DExperts in comparison with four baseline methods, in terms of toxicity, topicality, and fluency. We first describe the agreed approach for reproduction within the ReproHum project and detail the configuration of the original evaluation, including necessary adaptations for reproduction. Then, we make a comparison of our reproduction results with those reported in the reproduced paper. Interestingly, we observe how the human evaluators in our experiment appreciate higher quality in the texts generated by DExperts in terms of less toxicity and better fluency. All in all, new scores are higher, also for the baseline methods. This study contributes to ongoing efforts in ensuring the reproducibility and reliability of findings in NLP evaluation and emphasizes the critical role of robust methodologies in advancing the field.

The evaluation of Natural Language Generation (NLG) systems has recently aroused much interest in the research community, since it should address several challenging aspects, such as readability of the generated texts, adequacy to the user within a particular context and moment and linguistic quality-related issues (e.g., correctness, coherence, understandability), among others. In this paper, we propose a novel technique for evaluating NLG systems that is inspired on the triangular test used in the field of sensory analysis. This technique allows us to compare two texts generated by different subjects and to i) determine whether statistically significant differences are detected between them when evaluated by humans and ii) quantify to what extent the number of evaluators plays an important role in the sensitivity of the results. As a proof of concept, we apply this evaluation technique in a real use case in the field of meteorology, showing the advantages and disadvantages of our proposal.