I think it's fair to criticize this blog post for being unclear on what exactly is novel here; pre-training is a straighforward and old idea, but the blog post

I think it's fair to criticize this blog post for being unclear on what exactly is novel here; pre-training is a straighforward and old idea, but the blog post does not even mention this. Having accessible write ups for AI work is great, but surely it should not be confusing to domain experts or be written in such a way as to exacerbate the rampant oversimplification or misreporting in popular press about AI. Still, it is a cool mostly-experimental/empirical result, and it's good that these blog posts exist these days. For what it's worth, the paper predictably does a better job of covering the previous work and stating what their motivation was: "The experimental and evaluation protocols may be underestimating the quality of unsupervised representation learning for sentences and documents due to certain seemingly insignificant design decisions. Hill et al. (2016) also raises concern about current evaluation tasks in their recent work which provides a thorough survey of architectures and objectives for learning unsupervised sentence representations - including the above mentioned skip-thoughts. In this work, we test whether this is the case. We focus in on the task of sentiment analysis and attempt to learn an unsupervised representation that accurately contains this concept. Mikolov et al. (2013) showed that word-level recurrent language modelling supports the learning of useful word vectors and we are interested in pushing this line of work. As an approach, we consider the popular research benchmark of byte (character) level language modelling due to its further simplicity and generality. We are also interested in evaluating this approach as it is not immediately clear whether such a low-level training objective supports the learning of high-level representations." So, they question some built in assumptions from the past by training on lower-level data (characters), with a bigger dataset and more varied evaluation. The interesting result they highlight is that a single model unit is able to perform so well with their representation: "It is an open question why our model recovers the concept of sentiment in such a precise, disentangled, interpretable, and manipulable way. It is possible that sentiment as a conditioning feature has strong predictive capability for language modelling. This is likely since sentiment is such an important component of a review" , which I tend to agree with... train a on a whole lot of reviews, it's only natural to train a regressor for review sentiment.