Hacking stylometry with multiple voices: Imaginary writers can override authorial signal in Delta.

This article investigates the limits of stylometric authorship attribution, focusing on how certain authors' use of pseudonyms or heteronyms can override typical authorial signals detected by Burrows's Delta, a statistical method for clustering texts by authorial style. The study examines Portuguese poet Fernando Pessoa, who created multiple heteronyms—distinct literary alter-egos with fully developed personalities and writing styles—that exhibit strong stylometric autonomy indistinguishable from separate authors. In contrast, the French novelist Romain Gary's pseudonym Emile Ajar shows some stylistic independence but less consistently than Pessoa's heteronyms, while Gary's other pennames lack such autonomy. These findings suggest a continuum between mere pseudonyms, which do not significantly alter authorial style, and fully developed heteronyms that can deceive stylometric methods by producing multiple, distinct authorial voices.