Social norms can help solving cooperation dilemmas, constituting a key ingredient in systems of indirect reciprocity (IR). Under IR, agents are associated with different reputations, whose attribution depends on socially adopted norms that judge behaviors as good or bad. While the pros and cons of having a certain public image depend on how agents learn to discriminate between reputations, the mechanisms incentivizing agents to report the outcome of their interactions remain unclear, especially when reporting involves a cost (costly reputation building). Here we develop a new model---inspired in evolutionary game theory---and show that two social norms can sustain high levels of cooperation, even if reputation building is costly. For that, agents must be able to anticipate the reporting intentions of their opponents. Cooperation depends sensitively on both the cost of reporting and the accuracy level of reporting anticipation.

The objective of my research project is the formal treatment of memory issues in Intelligent Software Agents. I extend recent work which proposed a (partial) formalization of SOAR architecture in modal logic, reasoning on a particular type of agents: resource-bounded agents. I introduce explicit treatment of time instants and time intervals by means of Metric Temporal Logic, both in the background logic and in mental operations.

While constraints are ubiquitous in artificial intelligence and constraints are also commonly used in machine learning and data mining, the problem of learning constraints from examples has received less attention. In this paper, we discuss the problem of constraint learning in detail, indicate some subtle differences with standard machine learning problems, sketch some applications and summarize the state-of-the-art.

Unsupervised learning is widely recognized as one of the most important challenges facing machine learning nowadays. However, in spite of hundreds of papers on the topic being published every year, current theoretical understanding and practical implementations of such tasks, in particular of clustering, is very rudimentary. This note focuses on clustering. The first challenge I address is model selection---how should a user pick an appropriate clustering tool for a given clustering problem, and how should the parameters of such an algorithmic tool be tuned? In contrast with other common computational tasks, for clustering, different algorithms often yield drastically different outcomes. Therefore, the choice of a clustering algorithm may play a crucial role in the usefulness of an output clustering solution. However, currently there exists no methodical guidance for clustering tool selection for a given clustering task. I argue the severity of this problem and describe some recent proposals aiming to address this crucial lacuna.

Human communication is multimodal and includes elements such as gesture and facial expression along with spoken language. Modern technology makes it feasible to capture all such aspects of communication in natural settings. As a result, similar to fields such as genetics, astronomy and neuroscience, scholars in areas such as linguistics and communication studies are on the verge of a data-driven revolution in their fields. These new approaches require analytical support from machine learning and artificial intelligence to develop tools to help process the vast data repositories. The Distributed Little Red Hen Lab project is an international team of interdisciplinary researchers building a large-scale infrastructure for data-driven multimodal communications research. In this paper, we describe a machine learning system developed to automatically annotate a large database of television program videos as part of this project. The annotations mark regions where people or speakers are on screen along with body part motions including head, hand and shoulder motion. We also annotate a specific class of gestures known as timeline gestures. An existing gesture annotation tool, ELAN, can be used with these annotations to quickly locate gestures of interest. Finally, we provide an update mechanism for the system based on human feedback. We empirically evaluate the accuracy of the system as well as present data from pilot human studies to show its effectiveness at aiding gesture scholars in their work.

We present a novel approach to modeling stories using recurrent neural networks. Different story features are extracted using natural language processing techniques and used to encode the stories as sequences. These sequences can be learned by deep neural networks, in order to predict the next story events. The predictions can be used as an inspiration for writers who experience a writer's block. We further assist writers in their creative process by generating visualizations of the character interactions in the story. We show that suggestions from our model are rated as highly as the real scenes from a set of films and that our visualizations can help people in gaining deeper story understanding.

Current progresses on fine-grained recognition are mainly focus on learning the discriminative feature representation via introducing the visual supervisions e.g. part labels. However, it is time-consuming and needs the professional knowledge to obtain the accuracy annotations. Different from these existing methods based on the visual supervisions, in this paper, we introduce a novel feature named audio visual attributes via discovering the correlations between the visual and audio representations. Specifically, our unified framework is training with video-level category label, which consists of two important modules, the encoder module and the attribute discovery module, to encode the image and audio into vectors and learn the correlations between audio and images, respectively. On the encoder module, we present two types of feed forward convolutional neural network for the image and audio modalities. While an attention driven framework based on recurrent neural network is developed to generate the audio visual attribute representation. Thus, our proposed architecture can be implemented end-to-end in the step of inference. We exploit our models for the problem of fine-grained bird recognition on the CUB200-211 benchmark. The experimental results demonstrate that with the help of audio visual attribute, we achieve the superior or comparable performance to that of strongly supervised approaches on the bird recognition.

We propose a new neural network called Temporal-enhanced Convolutional Network (T-CN) for video-based person reidentification. For each video sequence of a person, a spatial convolutional subnet is first applied to each frame for representing appearance information, and then a temporal convolutional subnet links small ranges of continuous frames to extract local motion information. Such spatial and temporal convolutions together construct our T-CN based representation. Finally, a recurrent network is utilized to further explore global dynamics, followed by temporal pooling to generate an overall feature vector for the whole sequence. In the training stage, a Siamese network architecture is adopted to jointly optimize all the components with losses covering both identification and verification. In the testing stage, our network generates an overall discriminative feature representation for each input video sequence (whose length may vary a lot) in a feed-forward way, and even a simple Euclidean distance based matching can generate good re-identification results. Figure 1: The overall architecture of our proposed model. Experiments on the most widely used benchmark datasets demonstrate the superiority of our proposal, in comparison with the state-of-the-art.

Person images captured by public surveillance cameras often have low resolutions (LR) in addition to uncontrolled pose variations, background clutters and occlusions. This gives rise to the resolution mismatch problem when matched against the high resolution (HR) gallery images (typically available in enrolment), which adversely affects the performance of person re-identification (re-id) that aims to associate images of the same person captured at different locations and different time. Most existing re-id methods either ignore this problem or simply upscale LR images. In this work, we address this problem by developing a novel approach called Super-resolution and Identity joiNt learninG (SING) to simultaneously optimise image super-resolution and person re-id matching. This approach is instantiated by designing a hybrid deep Convolutional Neural Network for improving cross-resolution re-id performance. We further introduce an adaptive fusion algorithm for accommodating multi-resolution LR images. Extensive evaluations show the advantages of our method over related state-of-the-art re-id and super-resolution methods on cross-resolution re-id benchmarks.

Current deep learning methods for action recognition rely heavily on large scale labeled video datasets. Manually annotating video datasets is laborious and may introduce unexpected bias to train complex deep models for learning video representation. In this paper, we propose an unsupervised deep learning method which employs unlabeled local spatial-temporal volumes extracted from action videos to learn midlevel video representation for action recognition. Specifically, our method simultaneously discovers mid-level semantic concepts by discriminative clustering and optimizes local spatial-temporal features by two relatively small and simple deep neural networks. The clustering generates semantic visual concepts that guide the training of the deep networks, and the networks in turn guarantee the robustness of the semantic concepts. Experiments on the HMDB51 and the UCF101 datasets demonstrate the superiority of the proposed method, even over several supervised learning methods.