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

Understanding Why Large Language Models Struggle to Count Letters in Words

In recent discussions, you might have seen instances where large language models (LLMs) are humorously criticized for their inability to count specific letters within words—such as the number of “R”s in “Strawberry.” This raises an interesting question: why do these advanced models sometimes fall short on seemingly simple tasks?

The Inner Workings of LLMs

At their core, LLMs process text by dividing it into small units known as “tokens.” These tokens can be words, parts of words, or even individual characters, depending on the language model’s design. Following this, each token is transformed into a numerical format called a “vector”—a multi-dimensional array that captures semantic and syntactic information about the token.

These vectors are then fed into the model’s neural network layers, which generate responses or predictions based on learned patterns. However, this process isn’t designed to retain a detailed, character-by-character memory of the original text.

Why Counting Letters is Challenging

Since LLMs convert text into abstract vectors rather than explicit character data, they lack precise awareness of individual letters once the input has been tokenized and embedded. Consequently, the models do not “know” how many times a specific letter appears in a word like “Strawberry.” Their training focuses more on understanding language context, syntax, and semantics rather than tracking specific character counts.

Visual Reference

For a clearer understanding, you can explore an illustrative diagram here: https://www.monarchwadia.com/pages/WhyLlmsCantCountLetters.html. (Please note that direct image sharing may be restricted on some platforms, but the resource offers valuable insights.)

Final Thoughts

While it’s tempting to think of LLMs as perfect language machines, it’s important to recognize their limitations. Tasks requiring pinpoint precision at the character level—like counting specific letters—are outside their primary design scope. Recognizing these nuances helps in setting realistic expectations about what these models can achieve.


Interested in the science behind AI and language models? Stay tuned for more insights and explanations!

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