In an experiment with animated stimuli, should I accept answers during Animation Time and count it into the Response Time? In an experimental task where the response time is an important variable to compare two groups with different conditions, and there are animated stimuli (movement), should the response be accepted during the movement and the animation time be included in the response time measurement?
For instance, suppose that I have a categorization-like task where there are two kinds of movements for the objects, and those movements are presented through a 500ms animation. If a participant manages to notice the expected answer before the animation ends and press the button in, like, 450ms, should I accept this response?
I'm worried that some participants might wait until it's finished to answer while some others might not, and that might add some noise which I'm not sure about the significance (maybe for lack of experience).
You could solve this problem telling your participant that they have to answer as soon as they spot the right answer or if you do not want them to answer before the end of the stimuli you can disable answers before the end of the stimuli (normally you write what you expect in the experiment introduction screen).
If you let (want) your participant to answer as soon as they spot the right answer then you should consider as time response the time they took to answer. In concrete:
if the stimuli are presented at time 0 and last 200ms and your participant answer at time 50ms you should record them as answer time 50ms.
As far as I understood you are interested in seeing how long it takes for your participants to spot the right answer. So if you wait till the end of the stimuli for recording their answer you might just see how fast they are in pressing the bottom and not how fast they spot the right answer.