Final answer:
The learning curve is the key factor that increases production rates when a task is practised, as it reflects gains in speed and efficiency with experience.
Step-by-step explanation:
The factor responsible for an increase in production rates as a new task is repeated and practiced is known as the learning curve. This concept reflects the increased speed and efficiency that workers develop over time as they become more familiar with a task. Factors such as human capital, physical capital, and technology synergize to improve productivity, enabling workers to perform tasks more quickly and efficiently as they gain experience.