Abstract
This paper addresses the need to perform laboratory activities in secondary education science subjects, and what prospective science teachers feel while they themselves are doing these activities in their initial training. A laboratory activity based on the calculation of the oscillation period of a simple pendulum was done with 12 prospective teachers at the University of Extremadura, who were specializing in Biology/Geology, Physics/Chemistry, and Mathematics. When they had finished the activity they filled out a questionnaire about the difficulty, reasoning, capability, and emotions they had experienced in each of the stages needed to resolve the problem. The results showed how, as they go developing the stages of scientific methods, prospective teachers improve their reasoning and capability, and change negative emotions into positive ones, ending with being able to solve the problem on their own.