Instruction Fine-tuning (IFT) is a crucial phase in building large language models (LLMs). Previous works mainly focus on the IFT’s role in the transfer of behavioral norms and the learning of additional world knowledge. However, the understanding of the underlying mechanisms of IFT remains significantly limited. In this paper, we design a knowledge intervention framework to decouple the potential underlying factors of IFT, thereby enabling individual analysis of different factors. Surprisingly, our experiments reveal that attempting to learn additional world knowledge through IFT often struggles to yield positive impacts and can even lead to markedly negative effects. Further, we discover that maintaining internal knowledge consistency before and after IFT is a critical factor for achieving successful IFT. Our findings reveal the underlying mechanisms of IFT and provide robust support for some very recent and potential future works.

“Instruction Fine-Tuning(IFT) emerges as an essential step of training large language models torobustly carry out tasks of interest. However, there lacks a systematic investigation about theunderlying mechanisms of instruction fine-tuning, particularly on the forgetting phenomenonafter IFT, known as alignment tax. Therefore, to understand the mechanism of IFT from theforgetting perspective, we investigate the alternation of the text pattern and knowledge withinmodels throughout the entire IFT process. Specifically, we restore fine-tuned models to their baseversion by training them on the data sharing a similar distribution with the pre-training corpusand compare their results Our experiment indicates that there is a stage transition of forgettingduring IFT process: (1) Pseudo Forgetting: in this stage, models mainly shift their familiar textpattern away from pre-training data format while the world knowledge is preserved. Consequently,models will recover to their original performance when they are restored to the base version. (2)Actual Forgetting: in this stage, models forget the acquired knowledge as well. Therefore, theyfail to reach the original performance even if they are restored to the base version.”

Syntactically Controlled Paraphrase Generation (SCPG), which aims at generating sentences having syntactic structures resembling given exemplars, is attracting more research efforts in recent years. We took an empirical survey on previous SCPG datasets and methods and found three tacitly approved while seldom mentioned intrinsic shortcomings/trade-offs in terms of data obtaining, task formulation, and pre-training strategies. As a mitigation to these shortcomings, we proposed a novel Dual-Stage Multi-Task (DSMT) pre-training scheme, involving a series of structure-oriented and syntax-oriented tasks, which, in our opinion, gives sequential text models the ability of com-prehending intrinsically non-sequential structures like Linearized Constituency Trees (LCTs), understanding the underlying syntactics, and even generating them by parsing sentences. We performed further pre-training of the popular T5 model on these novel tasks and fine-tuned the trained model on every possible variant of SCPG task in literature, finding that our models significantly outperformed (up to 10+ BLEU-4) previous state-of-the-art methods. Finally, we carried out ablation studies which demonstrated the effectiveness of our DSMT methods and emphasized on the SCPG performance gains compared to vanilla T5 models, especially on hard samples or under few-shot settings.