In Ian McEwan's "Saturday," the concept of Mentalese is introduced as a form of pre-verbal language. This unique language functions as a complex matrix, quickly processing and compressing meaning while infusing it with emotional context. Rather than being a structured language, it operates on a more instinctive level, allowing individuals to convey ideas and feelings rapidly without the need for words.

The author illustrates this by describing a moment where a character perceives a flash of red out of the corner of his eye. This sudden visual stimulus is immediately interpreted as an idea imbued with emotion, carrying an essence of danger and urgency. This response showcases how individuals internalize experiences and perceptions, turning them into personal interpretations that reflect their inner world rather than the external reality.