A long-term goal of artificial intelligence is to have an agent execute commands communicated through natural language. In many cases the commands are grounded in a visual environment shared by the human who gives the command and the agent. Execution of the command then requires mapping the command into the physical visual space, after which the appropriate action can be taken. In this paper we consider the former. Or more specifically, we consider the problem in an autonomous driving setting, where a passenger requests an action that can be associated with an object found in a street scene. Our work presents the Talk2Car dataset, which is the first object referral dataset that contains commands written in natural language for self-driving cars. We provide a detailed comparison with related datasets such as ReferIt, RefCOCO, RefCOCO+, RefCOCOg, Cityscape-Ref and CLEVR-Ref. Additionally, we include a performance analysis using strong state-ofthe-art models. The results show that the proposed object referral task is a challenging one for which the models show promising results but still require additional research in natural language processing, computer vision and the intersection of these fields. The dataset can be found on our website: http:// macchina-ai.eu/

In recent years, we have seen significant steps taken in the development of self-driving cars. Multiple companies are starting to roll out impressive systems that work in a variety of settings. These systems can sometimes give the impression that full self-driving is just around the corner and that we would soon build cars without even a steering wheel. The increase in the level of autonomy and control given to an AI provides an opportunity for new modes of human-vehicle interaction. However, surveys have shown that giving more control to an AI in self-driving cars is accompanied by a degree of uneasiness by passengers. In an attempt to alleviate this issue, recent works have taken a natural language-oriented approach by allowing the passenger to give commands that refer to specific objects in the visual scene. Nevertheless, this is only half the task as the car should also understand the physical destination of the command, which is what we focus on in this paper. We propose an extension in which we annotate the 3D destination that the car needs to reach after executing the given command and evaluate multiple different baselines on predicting this destination location. Additionally, we introduce a model that outperforms the prior works adapted for this particular setting.

The task of visual grounding requires locating the most relevant region or object in an image, given a natural language query. So far, progress on this task was mostly measured on curated datasets, which are not always representative of human spoken language. In this work, we deviate from recent, popular task settings and consider the problem under an autonomous vehicle scenario. In particular, we consider a situation where passengers can give free-form natural language commands to a vehicle which can be associated with an object in the street scene. To stimulate research on this topic, we have organized the Commands for Autonomous Vehicles (C4AV) challenge based on the recent Talk2Car dataset. This paper presents the results of the challenge. First, we compare the used benchmark against existing datasets for visual grounding. Second, we identify the aspects that render top-performing models successful, and relate them to existing state-of-the-art models for visual grounding, in addition to detecting potential failure cases by evaluating on carefully selected subsets. Finally, we discuss several possibilities for future work.

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Humans often leverage spatial clues to categorize scenes in a fraction of a second. This form of intelligence is very relevant in time-critical situations (e.g., when driving a car) and valuable to transfer to automated systems. This work investigates the predictive power of solely processing spatial clues for scene understanding in 2D images and compares such an approach with the predictive power of visual appearance. To this end, we design the laboratory task of predicting the identity of two objects (e.g., "man" and "horse") and their relationship or predicate (e.g., "riding") given exclusively the ground truth bounding box coordinates of both objects. We also measure the performance attainable in Human Object Interaction (HOI) detection, a real-world spatial task, which includes a setting where ground truth boxes are not available at test time. An additional goal is to identify the principles necessary to effectively represent a spatial template, that is, the visual region in which two objects involved in a relationship expressed by a predicate occur. We propose a scale-, mirror-, and translation-invariant representation that captures the spatial essence of the relationship, i.e., a canonical spatial representation. Tests in two benchmarks reveal:(1) High performance is attainable by using exclusively spatial information in all tasks. (2) In HOI detection, the canonical template outperforms the rest of spatial, visual, and several state-of-the-art baselines. (3) Simple fusion of visual and spatial features substantially improves performance. (4) Our methods fare remarkably well with a small amount of data and rare categories. Our results obtained on the Visual Genome (VG) and the Humans Interacting with Common Objects -Detection (HICO-DET) datasets indicate that great predictive power can be obtained from spatial clues alone, opening up possibilities for performing fast scene understanding at a glance.INDEX TERMS Spatial understanding, spatial layout, computer vision, vision and scene understanding. I. INTRODUCTION 1A Well-researched concept in cognitive science is the 2 gist, or the initial representation of a scene obtained 3 in a brief glance. The gist may include semantic content 4 (e.g., "is a classroom"), the identity of a few objects (e.g., 5"there are books"), and the spatial layout [1]. Humans can 6 categorize scenes in a fraction of a second (∼13-250 ms) 7[1], [2]. Generally, more detailed scenes and finer-grained 8