  Large Language Models (LLMs) have demonstrated remarkable abilities, one of
the most important being In-Context Learning (ICL). With ICL, LLMs can derive
the underlying rule from a few demonstrations and provide answers that comply
with the rule. Previous work hypothesized that the network creates a "task
vector" in specific positions during ICL. Patching the "task vector" allows
LLMs to achieve zero-shot performance similar to few-shot learning. However, we
discover that such "task vectors" do not exist in tasks where the rule has to
be defined through multiple demonstrations. Instead, the rule information
provided by each demonstration is first transmitted to its answer position and
forms its own rule vector. Importantly, all the rule vectors contribute to the
output in a distributed manner. We further show that the rule vectors encode a
high-level abstraction of rules extracted from the demonstrations. These
results are further validated in a series of tasks that rely on rules dependent
on multiple demonstrations. Our study provides novel insights into the
mechanism underlying ICL in LLMs, demonstrating how ICL may be achieved through
an information aggregation mechanism.
