What does the Next Sentence Prediction (NSP) task involve in pre-training a model?

The Next Sentence Prediction (NSP) task is designed to train models to understand the relationships between pairs of sentences. Specifically, it involves determining whether a second sentence logically follows a first sentence in a coherent manner. This ability is crucial for various natural language processing tasks, including reading comprehension and dialogue systems, where understanding context and relationships between sentences is necessary.

By focusing on the task of identifying whether two sentences appear consecutively in a text, models can learn to recognize coherence and contextual transitions in language. This skill helps the model in effectively capturing the nuances of language usage, making it more adept at tasks that require an understanding of sentence flow and semantic connections.

The other options focus on tasks or features that do not align with the definition of the NSP task. Predicting the next token pertains more to language modeling tasks rather than the specific relationship between sentence pairs. Optimizing training speed and reducing training data size are operational considerations that relate to training processes but do not define the NSP task itself.