Millions of people post images and texts to express their feelings and point of views on social media everyday, especially on the short text social media such as Twitter or Weibo. As the images can provide important supplementary information for the text, many multimodal topic models have been developed to mine the topics from the multimodal social media content. We summarize three fundamental characteristics of the short text multimodal social media. The first is that the text of a short social media document generally belong to only one topic. The second is that the attached images can be relevant to multiple topics due to the rich information expressed in the images. The last is that although in most cases, text and images in social media posts are relevant, it should be noted that in a small number of cases, text and pictures are not relevant. However, most of the current multimodal topic models fail to model the these characteristics, and thus may produce low-quality topics. Based on these characteristics, we propose an unsupervised multimodal topic model SMMTM to model the short text multimodal social media documents. In the SMMTM model, only one topic is sampled for the the text while an image can belong to different topics. The correlation of the topics between the text and the images in a document are also formulated in an appropriate way. The experiments on three short text social media datasets with four evaluation metrics show the advantages of our model over the existing models.

Curiosity affects users' selections of items, and it motivates them to explore the items regardless of their interests. This phenomenon is particularly common in social networks. However, the existing social-based recommendation methods neglect such feature in social network, and it may cause the accuracy decease in recommendation. What's more, only focusing on simulating the users' preferences can lead to information cocoons. In order to tackle the problem, we propose a novel Curiosity Enhanced Bayesian Personalized Ranking (CBPR) model. Our model makes full use of the theories of psychology to model the users' curiosity aroused when facing different opinions. The experimental results on two public datasets demonstrate the advantages of our CBPR model over the existing models.