What is defined as the speed of responding to signals with body movement?

The correct answer is reaction time. This term refers specifically to the duration it takes for an individual to respond to a stimulus, which can involve detecting a signal and then executing a body movement in reaction. This concept is crucial in fields such as psychology and physiology, where understanding the speed of response can correlate with cognitive processing and motor skill effectiveness.

While the concept of response time is related and often used interchangeably with reaction time, it's more general and can include any form of response, not just physical movement. Movement speed, on the other hand, refers more to how quickly a body can move once a decision has been made, rather than the time taken to decide to move in the first place. Impulse response is typically used in contexts related to systems and signals, especially in engineering and physics, which does not apply here as it pertains more to the system's output rather than an individual's physical reaction.