What is the primary focus of Donder's pioneering experiment?

Donder's pioneering experiment primarily focused on the time taken to respond to stimuli, which was groundbreaking in the field of cognitive psychology. This experiment established a method for quantifying the duration of mental processes, notably through tasks that required participants to make decisions based on different types of stimuli. By measuring reaction times, Donder was able to infer the complexity of cognitive processes involved in decision-making and other mental activities.

In contrast, while understanding mental processes is certainly a significant aspect of cognitive psychology, the specific intent of Donder's work was to provide empirical data about the time taken to respond, thus linking reaction time with cognitive effort. The other options, such as identifying specific sensations and measuring emotional responses, do not align with Donder's primary aim, which was directed towards time measurement in cognitive tasks rather than the qualitative aspects of mental experiences or emotional states.