Conventional neural networks including Transformers encounter the catastrophic forgetting problem during sequential task learning, where learning new tasks interferes with previously learned knowledge. Existing memory replay and regularization methods cannot effectively eliminate interference among different tasks. Soft parameter sharing methods usually necessitate a large amount of additional parameters for learning each task, and task identity information is essential for leveraging task-specific parameters. To this end, we propose Remembering Transformer leveraging an adapter mixtures architecture enhanced by a generative routing mechanism for efficient task retention. In generative routing, input samples are allocated to the most relevant expert adapters based on a reconstruction loss. Moreover, unlike existing studies on soft parameter sharing that do not consider model capacity limitations, we investigate a challenging setting where the number of task-specific parameters is constrained. In particular, we devise an adapter fusion strategy to aggregate resembling experts based on similarity matching and knowledge distillation. Extensive empirical results measured by task accuracy, forgetting rate, and memory footprint, demonstrate that Remembering Transformer significantly enhances knowledge retention without task identity information. The proposed method surpasses various conventional methods with enhanced parameter efficiency in a broad range of incremental learning tasks.

Continual learning with deep neural networks presents challenges distinct from both the fixed-dataset and convex continual learning regimes. One such challenge is plasticity loss, wherein a neural network trained in an online fashion displays a degraded ability to fit new tasks. This problem has been extensively studied in both supervised learning and off-policy reinforcement learning (RL), where a number of remedies have been proposed. Still, plasticity loss has received less attention in the on-policy deep RL setting. Here we perform an extensive set of experiments examining plasticity loss and a variety of mitigation methods in on-policy deep RL. We demonstrate that plasticity loss is pervasive under domain shift in this regime, and that a number of methods developed to resolve it in other settings fail, sometimes even performing worse than applying no intervention at all. In contrast, we find that a class of ``regenerative'' methods are able to consistently mitigate plasticity loss in a variety of contexts, including in gridworld tasks and more challenging environments like Montezuma's Revenge and ProcGen.

We aim to understand how people assess human likeness in navigation produced by people and artificially intelligent (AI) agents in a video game. To this end, we propose a novel AI agent with the goal of generating more human-like behavior. We collect hundreds of crowd-sourced assessments comparing the human-likeness of navigation behavior generated by our agent and baseline AI agents with human-generated behavior. Our proposed agent passes a Turing Test, while the baseline agents do not. By passing a Turing Test, we mean that human judges could not quantitatively distinguish between videos of a person and an AI agent navigating. To understand what people believe constitutes human-like navigation, we extensively analyze the justifications of these assessments. This work provides insights into the characteristics that people consider human-like in the context of goal-directed video game navigation, which is a key step for further improving human interactions with AI agents.

The rapid pace of recent research in AI has been driven in part by the presence of fast and challenging simulation environments. These environments often take the form of games; with tasks ranging from simple board games, to competitive video games. We propose a new benchmark - Obstacle Tower: a high fidelity, 3D, 3rd person, procedurally generated environment. An agent in Obstacle Tower must learn to solve both low-level control and high-level planning problems in tandem while learning from pixels and a sparse reward signal. Unlike other benchmarks such as the Arcade Learning Environment, evaluation of agent performance in Obstacle Tower is based on an agent's ability to perform well on unseen instances of the environment. In this paper we outline the environment and provide a set of baseline results produced by current state-of-the-art Deep RL methods as well as human players. These algorithms fail to produce agents capable of performing near human level.