  In-context learning (ICL) is an emerging capability of large autoregressive
language models where a few input-label demonstrations are appended to the
input to enhance the model's understanding of downstream NLP tasks, without
directly adjusting the model parameters. The effectiveness of ICL can be
attributed to the strong language modeling capabilities of large language
models (LLMs), which enable them to learn the mapping between input and labels
based on in-context demonstrations. Despite achieving promising results, the
causal nature of language modeling in ICL restricts the attention to be
backward only, i.e., a token only attends to its previous tokens, failing to
capture the full input-label information and limiting the model's performance.
In this paper, we propose a novel ICL method called Repeated Demonstration with
Sliding Causal Attention, (RdSca). Specifically, we duplicate later
demonstrations and concatenate them to the front, allowing the model to
`observe' the later information even under the causal restriction. Besides, we
introduce sliding causal attention, which customizes causal attention to avoid
information leakage. Experimental results show that our method significantly
improves the input-label mapping in ICL demonstrations. We also conduct an
in-depth analysis of how to customize the causal attention without training,
which has been an unexplored area in previous research.
