El estudio caracteriza perfiles de la competencia mirar profesionalmente el razonamiento proporcional de 14 estudiantes para profesor de matemáticas de secundaria, al identificar e interpretar características del razonamiento proporcional y decidir sobre cómo continuar la enseñanza. Identificamos tres perfiles de estudiantes para profesor considerando el desempeño en las destrezas (atender, interpretar y decidir): perfil notable, caracterizado por un desempeño alto en las tres destrezas; perfil mixto, caracterizado por un desempeño desigual; y perfil emergente, que evidencia dificultades significativas en las tres destrezas. Estos perfiles revelan dos características en el aprendizaje de esta competencia docente: i) la dificultad de los estudiantes para profesor, al considerar al mismo tiempo varios elementos matemáticamente relevantes; y ii) la no linealidad entre las destrezas., The study characterizes profiles of professional noticing proportional reasoning of fourteen prospective secondary mathematics teachers as they attend to and interpret characteristics of proportional reasoning to decide how to proceed with teaching. We characterize three prospective secondary teachers' profiles regarding the development of the three skills (attend to, interpret and decide). The notable profile was characterized by high performance in the three skills; the mixed profile was characterized by uneven performance across the skills; and the emerging profile when prospective teachers had difficulties in the three skills. These profiles reveal two features of the learning of professional noticing: (i) the difficulty in simultaneously considering multiple mathematically relevant elements, and (ii) the non-linearity between the skills.