Can ChatGPT Learn to Count Letters?

In this paper we explore if ChatGPT can learn to count letters. Since the introduction of ChatGPT two years ago, Large Language Model (LLM) based tools have shown impressive capabilities to solve mathematical problems or to answer questions on almost any topic [1]. In fact, evaluation benchmarks have to be revised frequently to make then harder as LLM performance improves continuously [2]. The development of LLMs has also been hectic with new models presented by large companies such as Google with Gemini or Gemma, Meta with Llama or x.AI with Grok. OpenAI has also released newer versions and improvements of their Generative Pre-trained Transformer (GPT) family such as GPT4 [3] and its variants GPT4o and GPT4o1. Those foundational models are then adapted to answer questions or interact with users and complemented with other functionalities to implement conversational tools like ChatGPT. Despite these astonishing results, there are some simple tasks that LLMs struggle with, for example arithmetic operations [4] or even counting the occurrences of a given letter in a word. For example, many LLMs failed to count the number of "r" in strawberry