Take the 2-minute tour ×
Cognitive Sciences Stack Exchange is a question and answer site for practitioners, researchers, and students in cognitive science, psychology, neuroscience, and psychiatry. It's 100% free, no registration required.

I am an undergrad, I am planning to do some research to see how much I enjoy it before I apply for grad programs.

I am researching the effects of a certain characteristic of a presenter making people upset, uncomfortable, aggravated or displeased during a short clip like a TV commercial. My plan is to have subjects watch a short clip with a presenter and see if they are they aggravated, upset, uncomfortable with the presenter based on that one characteristic changing and compare this across demographics. I do not have much experience with setting up and performing experiments so any help would be much appreciated.

How do I quantify how upset, uncomfortable, aggravated or displeased the subject felt?

How do I make sure that every subjects experience is the same expect for that one factor?

Do I have to do anything special because I will not be able to run the same test on the same exact subject?

I really want to know how to best perform this experiment.

share|improve this question
add comment

4 Answers 4

Without knowing exactly what the factor you are interested in is, it is hard to predict how feasible it would be to manipulate it. For example, is it possible to make two videos of the speaker, one with the factor, and one without, with nothing else changing? My guess is that you probably can't do this, so I'm going to focus on how you might be able to run the experiment without that kind of very specific control.

One option would be to make several videos, half of them with the critical factor, and half without. There will be lots of other things that vary between these videos, but as long as the only thing that varies systematically is the factor you are interested in, then you can run an informative experiment.

You asked: How do I make sure that every subjects experience is the same expect for that one factor? The answer is that you can't really do this. You can try to get close, but subjects will always have slightly different experiences. This is why we need to run many subjects to determine if an effect is reliable. Any given subject may just be tired/hungry/cranky when they come to the experiment and this will affect your results. But, if you run lots of subjects then it is likely that tired/hungry/cranky subjects will be in both conditions, and therefore on average won't impact your conclusions.

Depending on how long the videos are, you could potentially show multiple videos to a single subject, and measure their emotional responses to each one. This is a within-subject design, and the advantage of this is that it controls for some of the random variation (tired/hungry/crankiness) between different subjects in your experiment. If subject A tends to be crankier than subject B, it will introduce noise into your results if each subject only sees one kind of video. But if subjects see both kinds of videos, you can test whether videos with the factor tended to make subjects more aggravated, controlling for their 'baseline' level of aggravation. If the videos are longer, then you could just show one kind of video to each subject (a between-subjects design) but this will probably require collecting data from more subjects to wash out the noise of some subjects being more prone to aggravation than others.

share|improve this answer
    
I know that there are repositories of images for affect-related experiments that contain neutral, positive and negative images (such as the NIMH system). It seems possible that there may be a similar repository of video clips. –  lea Jul 2 at 5:40
add comment

Polygraph-style measurements might be useful to get some hard data - emotional excitement and stress have biological effects, and measuring+recording heart rate and blood pressure can be done rather simply.

For qualitative analysis, it would be useful to capture as much as you can of the experiment - e.g. a video recording of the face to analyse expression changes, as well as a whole body video recording. You also need to have a solid way to sync the recording with the shown stimulus, so you can match the event times afterwards.

share|improve this answer
    
Thanks for the information and how cheap would all that be? And is there open source software for the facial recognition that is available or software that is cheap for students? –  user18101 Jul 1 at 23:21
add comment

I see you want to measure reactions based on viewing a clip by demographics.

How do I quantify how upset, uncomfortable, aggravated or displeased the subject felt?

You quantify it by gathering hard data: heart rate, blood pressure, pupil dilation (if you can get it in the video), and whatever other similar experiments have measured. You have a standard questionnaire. But you should also attempt to get some qualitative data.

How do I make sure that every subjects experience is the same except for that one factor?

You do the best you can, document any possible failure points, and have a system to randomize who gets what.

Do I have to do anything special because I will not be able to run the same test on the same exact subject?

You should review the literature on these types of experiments and try to follow the safeguards other experimenters used. I recall a leading theoretician complained that no-one follows the safeguards established by the person who established different ways rats had of sensing where the food was. You've got to take great pains to ensure you follow the best practices of doing this research, or you'll undermine your credibility as a researcher and the credibility of your results.

share|improve this answer
add comment

Another experimental approach is to have the subjects perform some task before and after viewing the video, where their individual task performance varies according to the subject's emotional state: comfort vs discomfort, relaxation vs agitation, calm vs upset. Ideally, the task is simple and not something that involves thought or skill. In this setup, your goal is to have subjects reveal their emotional state through their performance in this task, and not through any direct revelation or awareness.

The other advantage of this approach is that you aren't signaling to the subjects that you are testing for their emotional state.

An example of such a task is interpreting the emotional state of another person's facial expression. For example, the task might be to evaluate a series of photos with ambiguous facial expressions and put them into two categories: "Trusted" vs. "Not trusted". (You can put this in a simple setting: "Imagine that you are in the library. You need to step outside to take a call. Would you trust this person to watch your valuables (computers, books) for a few minutes?")

Though I don't have a reference for you, I believe I read some research on this that found that subjects were more likely to interpret ambiguous facial expressions positively if the subject was in a positive emotional state.

There are even simpler tasks that might be good candidates. You could probably find a list of candidates by reading the experimental research literature.

Again, all you care about in this experiment is the difference between each individual's performance when they are upset vs. at ease.

You can test the validity of this experimental method independently. Recruit some subjects for a randomized control trial. Instead of showing them the video, you will directly irritate them (stimulus group) or not (control group). Your stimulus could be 15 second audio recording of fingernails scraping over a blackboard. For the control, you could use 15 second audio recording of a sin wave tone (around 400 hz). Your performance on pre- and post-tasks should be very different for the stimulus group and show no change in the control group. (For best results, you should randomly assign subjects to groups, and even you should not know who is in what group -- "double blind".)

The besides validity testing, this experiment will give you a standard of comparison to evaluate just how irritating or upsetting your videos are, compared to fingernails scraping over a blackboard.

EDIT: If you know the TV show "Mythbusters", they have done experiments involving sleep deprivation and also drinking where the subjects had to perform the same task before and after the stimulus. As I recall, the "beer goggles" episode involved a task of scoring faces for attractiveness before and after drinking heavily.

EDIT: The other answers advise you to measure physiological phenomena through direct sensors. Even if you can get the sensors and data recorders, analyzing the data can be more complicated than it sounds. It's not so easy to aggregate those data into a reliable overall assessment of emotional state along a single dimension: at ease vs upset. Inferring emotional state from physiological variables is a whole research field in itself!

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.