Why LLM’s can’t count the R’s in the word “Strawberry”

Understanding Why Large Language Models Struggle to Count Specific Letters in Words

In recent discussions, you might have seen that large language models (LLMs) sometimes falter when asked to perform seemingly simple tasks — such as counting how many times a particular letter appears in a word, for example, “Strawberry.” This raises an interesting question: why do these advanced models often struggle with such basic counting tasks?

The Underlying Process of LLMs

At their core, LLMs process text by segmenting input into units called tokens. These tokens can be as small as individual characters or as large as words, depending on the model’s design. Once tokenized, the model transforms these tokens into numerical representations known as vectors. These vectors are the foundation for the model’s understanding and subsequent processing.

Why Counting Letters Is Challenging

Since LLMs are optimized for understanding context, semantics, and language patterns rather than precise character-level details, their internal representations do not preserve exact counts of individual characters. Essentially, when the input text is transformed into vectors, the detailed information about each letter gets blended into broader patterns. As a result, the model’s internal “memory” isn’t built for counting or tracking specific characters, making tasks like counting R’s in “Strawberry” inherently difficult.

Visualizing the Concept

For a clearer understanding, a helpful diagram explaining this process is available here. Although I can’t share images directly in this post, I recommend visiting the link for a visual breakdown of how tokenization and embedding contribute to this limitation.

Final Thoughts

While LLMs excel in generating coherent text, understanding context, and even completing complex language tasks, their architecture does not lend itself to precise letter counting. Recognizing these limitations helps us better appreciate both the strengths and weaknesses of current AI language models.


Interested in learning more about how language models process text? Explore the detailed explanation and visuals at the provided link.

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