|MadSci Network: Neuroscience|
It sounds like you conducted an interesting science project. In fact, the type of study you did is so good that many psychologists use that same type of test in their own research.
You asked if practicing would impact the results of your study. I would say that it most certainly could (and probably does to some extent) make people better at responding. There are a lot of ways you could examine this.
First, perhaps put people into different groups: A) no practice; B) some practice - say 30 seconds worth, or 10 button presses; or C) lots of practice - 3 or 4 minutes, or maybe 100 button presses. Then run them in the experiment. You might see a practice effect - that is that people with practice (either a little or a lot) do better than those without. Or you might even see a relationship that more practice leads to better results (that is, group C is better than group B is better than group A).
However, you might also consider that there are different TYPES of practice. What I described above is just button pressing practice, but what would you expect if you ran a subject through a real practice experiment (seeing the light and pressing the button). So they would practice the whole experiment. Do you think whole experiment practice would provide better training than just button pressing?? (I do.). But another twist is whether too much practice may not be a good thing. If you examined group C, you might see that they did better than the no practice (group A) people, but did worse than the little practice (group B) students. Maybe too much practice makes them tired. Perhaps you could figure out the optimum amount of practice to have.
But there are many other things that you mentioned that might be important to know also.
You talked about left-handed vs. right-handed….which is very important (using your dominant or non-dominant hand). You could ask people which is their dominant hand and have them use that one only. Or maybe have them use the non-dominant hand. About 10% of people are left-handed, but most things in our day-to-day world are made for right-handed people (think about scissors-they actually do make left-handed scissors for people who want them, but most are right-handed). If you think about it, left-handed people using their right hand might perform better than right-handed people using their left hand (since few things are built left-handed). Or maybe practice is more effective with your non-dominant hand than with your dominant hand. This might be a good example of the law of diminishing returns. Simply put, when you originally learn how to do something (like throw a frisbee, or hit a baseball, or play the piano), you see a LOT of improvement when you begin to practice. Each day of practice seems to make a big difference. But as you get better and better, the same amount of practice produces smaller increases in your performance.
Another thing you might find interesting is what stimulus you use to signal the person. In your previous experiment, you used a light. You might think about using different colored lights (does red or blue light work better than white light?) Or maybe pick a different sensory modality-like sound. Maybe examine some people with a light, and others using a whistle or bell. Which stimuli do you think people would respond better to? the light or the bell?? (I don't know).
Finally, I'd like to point out some other things that you might want to think about. First, you talk about a difference between 221 msec and 228 msec. Now, I know you haven't had statistics yet (fancy math that scientists use to see if results are "significantly" different from each other), but that seems like a small difference to me. I wonder if you repeated the experiment if you might get different results. Or if you repeated the experiment 10 times, and then took the average times, whether the left- and right-handed results would be the same. Don't get me wrong-some of the most important things discovered in science have been small differences, but what is MORE important is seeing small differences CONSISTENTLY (or reliably). With any sort of reaction time experiment there will be individual differences. People will perform differently (sometimes better, or maybe even worse) if you retest them.
Anyway, I hope this has helped and given you some new ideas. Best of luck with your project.
Josh Rodefer, Ph.D. Harvard Medical School (firstname.lastname@example.org)Here are some web sites that give some information or ideas about reaction time experiments:
Try the links in the MadSci Library for more information on Neuroscience.