  Tokenization significantly influences language models(LMs)' performance. This
paper traces the evolution of tokenizers from word-level to subword-level,
analyzing how they balance tokens and types to enhance model adaptability while
controlling complexity. Despite subword tokenizers like Byte Pair Encoding
(BPE) overcoming many word tokenizer limitations, they encounter difficulties
in handling non-Latin languages and depend heavily on extensive training data
and computational resources to grasp the nuances of multiword expressions
(MWEs). This article argues that tokenizers, more than mere technical tools,
should drawing inspiration from the cognitive science about human language
processing. This study then introduces the "Principle of Least Effort" from
cognitive science, that humans naturally seek to reduce cognitive effort, and
discusses the benefits of this principle for tokenizer development. Based on
this principle, the paper proposes that the Less-is-Better (LiB) model could be
a new approach for LLM tokenizer. The LiB model can autonomously learn an
integrated vocabulary consisting of subwords, words, and MWEs, which
effectively reduces both the numbers of tokens and types. Comparative
evaluations show that the LiB tokenizer outperforms existing word and BPE
tokenizers, presenting an innovative method for tokenizer development, and
hinting at the possibility of future cognitive science-based tokenizers being
more efficient.
