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Game Testing And Research: The Body And The Mind

April 7, 2011 Article Start Previous Page 2 of 4 Next

Specific Psychophysiological Measures

Electroencephalography (EEG)

When it comes to trying to access the central nervous system, EEG is one of the easiest measurement tools for game testing and research to turn to. This is because unlike higher resolution PET scans or fMRI measurement, EEG does not require participants to be placed, lying down and still, in large, expensive (and magnetic) machinery.

Rather, EEG operates through the use of electrodes on a player's skull that measure the electrical impulses generated by the brain.

EEG setups range from full electrode caps, which take an hour or more to attach and are capable of measuring specific activations in certain brain regions, to relatively simple headbands which are capable of only general brain wave analysis.

Thankfully, when it comes to game research, this latter less intrusive and expensive form of EEG does provide quite workable measures of engagement and emotion by measuring various different frequencies of brain activity (or brain waves).

In terms of these frequencies, the bands of interest are usually the:

  • Alpha band (8-14 hz) that reflects calm, mental work.
  • Beta band (14-30 hz) that reflects focused, engaged mental work
  • Delta band (1-4 hz) that reflects sleep, relaxation and fatigue
  • Theta band (4-8 hz) that reflects emotions and sensations

So if someone is playing a game and EEG records an increase in Beta wave function, then you can assume that the player is actively engaged in some kind of mental work.

The Star Wars Force Trainer relies on reading Beta waves via a simple EEG setup.

However, there are several disadvantages to EEG. The first is that it is relatively expensive compared to other measures, especially if you want to go for the full electrode cap, and is quite time-consuming and invasive to set up and use. For example, with a full electrode cap setup, each electrode must be very specifically placed, with the addition of conducting gel, which is usually applied using a needle to ensure good coverage. While the needle is not used to pierce the skin, it can still be somewhat unpleasant and I have known of participants with aversions to needles to even faint during this process.

Furthermore, as with all of these measures, EEG is somewhat prone to producing artifacts if players move too much or speak (speaking activates areas of the brain, of course). Another commonalty for all of the measures I will mention is that there are considerable individual differences in psychophysiology, which means that baseline measures must always be taken. This is especially important for EEG, since some individuals do not produce any activity in the Alpha band at all (but are otherwise normal).

Finally, EEG can be difficult to interpret. For example, if you detect increased Delta activity, it could be that your game is relaxing and therefore enjoyable. On the other hand, it may be that it is boring and tiring. Similarly increased Beta band activity may indicate your game is engaging, or perhaps that the player is disengaged and thinking about a particularly hard day they had at work.

Electromyography (EMG)

EMG is all about detecting the activation of muscles through the use of electrodes, which are attached to the relevant muscle (or muscles). So again, like EEG, (and like most of the measures I am mentioning) this method relies on detecting electric current. However, unlike EEG, EMG is a direct indication of activation in the peripheral nervous system.

EMG can be applied to basically any muscle -- for example, the muscles of the upper back could be examined to test tension or stress. But of particular interest in game research and testing is generally facial EMG. This is where electrodes are attached to specific facial muscles that are sad to be related to negative or positive emotional reactions.

Specifically these are muscles in the:

  • Brow (Corrugator supercilii) that register negative emotion (unpleasant valence)
  • Cheeks (Zygomaticus major) that register positive emotion (pleasant valence)
  • Area around the eyes (Orbicularis oculi) that are said to register expressions of enjoyment and "genuine pleasure" (whatever that is)

This makes facial EMG one of the few physiological measures that can actually tap the valence axis of the typical two-axis view of emotions. Furthermore, the sensitivity of facial EMG means that changes in these muscles that could otherwise be missed from direct observation, or facial analysis software, can be detected and used.

Working all three muscles.

However, once again EMG has its disadvantages. First of all, you still have to deal with individual differences, so baselines are required (although this is less of a problem with EMG as it is with other measures). Then there is the intrusive nature of electrodes being on a player's face, combined with wires hanging off them.

This may actually limit natural movement of the face, and since it gives and indication to players that their facial muscles are being recorded, they may themselves produce unnatural responses -- perhaps overemphasizing facial movements in an attempt to assist your data collection (something that may even occur subconsciously).

Finally, and this will become somewhat of a broken record (or a corrupt mp3 player), but there is always the possibility of artifacts in your data caused by electrical interference or non-target events -- excessive body movement for example, or your players talking.

Electrodermal Activity (EDA)

Electrodermal Activity (EDA) is also known as Galvanic Skin Response or Skin Conductance and, as the "electro" prefix hopefully gives away, is related to measuring changes in electric current on the skin. Specifically, changes in electric current caused by the activation of sweat glands.

EDA is typically taken by recorded electrodes to two fingers (or toes) and are probably most famous for their use in "lie detector" tests. Since it does only use two electrodes, this means that EDA is less expensive and somewhat easier to set up than other physiological methods. Although care should be taken that the digits to which the electrodes are attached are not moved much during data recording -- something that can obviously be a problem if controllers have to be manipulated easily.

In terms of what EDA measures, it is seen as reacting to emotional arousal and mental workload, and gives very distinctive "spikes" in response to emotional stimuli and workload. This means that EDA can be handy for at looking at specific events during gameplay -- although it can also be averaged over time and examined.

A single EDA response, showing latency, the response, and the recovery period.

However, as the graph above shows, there can be quite a time between a game event occurring and the EDA response -- usually between one to five seconds. There is also a recovery period in EDA that must pass before any further response can be registered. This is of course a problem if you have lots of events going on in your game, as some may be missed, and due to the time lag it may not be clear exactly what an individual EDA is in response to.

Furthermore, EDA is quite a sensitive and noisy signal, which means that it suffers from specificity problems -- in other words an increase in EDA may be because a player was talking, moving too much, is engaged in your game, or is thinking about how cute you are (or a combination of these factors).

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Nicholas Sweeney
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Great article, I really like how you clearly presented each method. Thanks for your contribution!

Graham McAllister
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Nice article, a very concise primer on the key biometric approaches used in user research today.

Tim Carter
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God help us if this is where game design is going. Game design as pure manipulation, devoid of an actual meeting of heart and mind between game designer and game player above the horizon of the spinal cortex. Human beings are more than just animals, no matter what science tells us.

In psychotherapy this is a similar debate: the symptomatic approach on the one hand, known as "the medical model" which tends to use stuff like drugs and electroconvulsive therapy (formerly known as "electroshock"); and on the other, humanistic therapies, which treat a human not as a puzzle to figure out, but simply as a human being.

Ben Lewis-Evans
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Hi Tim,

To use your comparison to psychotheorpy, in my opinion the answer, as it is with many of these extreme dicotomies, is to take the best of what works from both approaches and combine them.

Ultimately what comes from psychophysiology is just more information that designers can access. It still must be intrepreted, and combined with other sources of information (from designers and players) otherwise it is just numbers on a screen.

In other words, as with any information source, its meaning still comes ultimately from the interface between designers and players.

Mark Venturelli
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@ Carter

Biometrics are just a tool. Design is "manipulation", no matter what tools you use, and there is nothing wrong with that. You sound like an old man shaking a stick.

Also, this is is a highly questionable and prejudiced view of therapy, but this is way off-topic.

Jack Garbuz
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What I want to know about game testing is, when is any company going to use 40 or even 50 year olds to test games? Is there anyone at all even slightly interested in making video games more user friendly for people over a certain age? Has anyone even bothered to try to sit down a 64 year old (that's my age) with in front of a console with controller in hand to find out what it takes to get middle age and older people involved? Or are 70 million Americans to be forever completely written off as potential consumers of these interactive entertainment products?

Thomas Nocera
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Great observation, Jack. I want you to know I am, and have been working on creating a game franchise which will offer a much broader appeal. The non-traditional gamer makes a very attractive, but hard to capture game consumer. However, the games that I am developing have as design criteria to take full advantage of new game interface technologies, (no more use of those damned little joysticks and arrary of push button controls. You are of the generation that are on my board of advisors for the WAYBACK2 ( and together we are designing what Professor Peabody and his boy Sherman would have, had they only had the 3D and motion sensing technologies that did not arrive until 50 years after their original WAYBAC was introduced on the Adventures of Rocky and Bullwinkle. (Remember that "must see TV" of yesteryear?)

Jack Garbuz
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Of course I remember Rocky and Bullwinkle :) I will go to your website to check out what you have there. Thanks. Cheers.

Bart Stewart
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Jack, IMO that question deserves a feature article of its own.

Consider: who has the most money to spend on games? Older gamers who *make* more money, that's who! It's bizarre to me that that publishers insist on chasing the 18-34 demo to the exclusion of going (as Willie Sutton once said) where the money is. Of course there's a question as to who has more free time to actually play games, but the idea that the Atari 2600 generation of gamers like myself have all fallen off the face of the earth is a needlessly wasted business opportunity.

If the numbers show that older gamers don't buy as many games as the 18-34 crowd, could that be in part because the games being made obviously aren't intended to be fun for the post-50 gamer?

I agree; more games for and testing with older gamers would be a Good Thing. The idea that if you're over 50, the only game you want to play is Wii Bowling -- with help from the nursing home staff -- is foolish. On the other hand, it's true that these folks don't have the same twitch skills they did as kids. Some level of publisher interest in testing games so that they can be physically fun for these gamers would seem to be appropriate... or did game publishers stop liking money when I wasn't looking?

Jack Garbuz
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Well, Bart, as I have stated in other posts, I'm a 64 year old gamer, who has played roughly 350 video games, mostly shooters and some RPG's, since I retired just little over a decade ago. Now I will agree that getting old dogs to learn new tricks is definitely an uphill battle. Have not managed nudge any of my friends in my "baby boomer" age group to try. But there are many reasons for it, mainly fear of failure and the resultant embarrassment, and a general aversion to trying anything "new." It's a shame, because I consider video games, without doubt, the premiere entertainment medium of the 21st century. I could no longer see myself living without video games anymore than I could without the internet, computers, movies or books. I'm addicted.

But the industry is at least as much to blame as the oldsters themselves. It does ABSOLUTELY NOTHING in the slightest to even take anyone over age 35 into account. We don't even exist in their universe.

Is say that any game made COULD be adapted to take into account the needs of prospective older players, if only the industry even gave us a second thought! Simple, inexpensive adapations. Let me list a few of my ideas:

1. In options, to include the ability to change font sizes.

2. To include a true novice mode that is almost impossible to fail;

3. To include a walkthrough or guide, either in-game, or in a booklet, preferable in game, so that it could be called up when in novice mode, to tell the player what to do next if he or she is stuck. And/or include cheats and anything required to make it possible to continue and finish the game for anyone of any age group it they want to so so. Embarrassment and fear of failure is what keeps oldster from trying. They don't want to be embarrassed in front of their kids or grandkids.

The games themselves don't really have to be changed otherwise. Don't need a separate category of games for older people, but just a few adaptations that could be relatively cheap to implement, and could do AN AWFUL LOT to pull this ignored audience in.

It's not that game publishers stopped liking making of money. It's just that it's an industry started by kids, made for kids, and now they are growing up, but still remain somewhat immature in their collective thinking. They just need someone who can really think out of the box, a they claim they try to do, but I don't see much evidence of it. At least not from my perspective. Often, people mostly overlook the most obvious.

A huge audience simply being utterly ignored, not being marketed to or adapted to in the slightest. It's actually crazy when you really think about it.

And what annoys me, is I know how SIMPLE and relatively inexpensive it could be.

Again, any game can be fun to people of all ages, if all ages are taken into account. I have played them all, so I know whereof I speak. I happen to be partial to FPS's and some better RPG's, but every genre can be as appealing to oldsters as to youngsters IF someone just makes the slightest effort to bring them into the game.

Thomas Nocera
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Jack, I share your observation and am working on something big - not many of our generation doing game development, but the Kinect game interface is a game changer.

Contact me at tomnocera (at) yahoo dot com and I will share with you some of the details and see where it leads.

Jack Garbuz
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Thank you. BUt frankly, I don't think that 50 year olds need a special category of games for themselves. The same old games are fine, as long as they have accommodations for older newbies. As I mentioned in my post, what I think is needed is simply a fail proof novice mode, adjustable fonts, built in guides or walkthroughs, maybe cheats, and other accommodations to make it easier for a novice to get through the game from beginning to end without being frustrated into giving up prematurely. I don't think that a controller is that hard a thing to master, and I don't know if everyone wants to move around or dance around in front of a Kinect, I could be wrong on that score, since they have sold a large number of those. But I don't know how a Kinect would make playing Red Dead Redemption any easier.

But it's nice that you are working on something relevant. If you want to fill me in, you can reach me at jgarbuz (at)

Daniil Sarkisyan
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I am a 40ye novice at the Gamasutra so perhaps I missed the blog where the rich issue of elderly player's niche is discussed. If so, could you please point me the right direction?

I would like to second Jack's opinion that instead of designing special games segregating old players into separate back room, there is huge social and monetary potential to give them special roles in the usual games.

1) Spending quality time with your kids (or any kids), helping them and being appreciated for such help is extremely valuable commodity.
2) Choosing help-the-kids fun over alcohol "fun" is socially valuable. Plus it gives a good estimate of the monthly fees that game designers could count on.
3) There is no need to super innovative. One can implement widely known and accepted archetype of white-haired, unhurried, sometimes even "extravagant" Wise Old Wizard with extremely powerful spells.
4) Please stick to good old familiar keyboard + mouse and very standard interface! Please do not force dignified old wizard to aim quickly and precisely, while timely pushing convoluted sequences of buttons.

Adams Greenwood-Ericksen
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Since it's not general-access, I'm reproducing a comment I made on this article at the IGDA GUR sig linked-in group:

Very nicely (and succinctly) laid out synopsis of the primarily physiological measures available for (relatively) easy use in game development. I may have missed it, but it didn't look like you addressed eyetracking (or pupillometry, an associated and very low intrusiveness measure of arousal or cognitive stress). Mike Ambinder talked about this briefly at GDC this year, but I don't think he did it credit either. In my experience, eyetracking is a great asset for interface assessment, especially in conjunction with low intrusiveness measures like GSR, HRV, or pupillometry. These three measures are infamous for the "what the hell happened there?" effect, where the subject has an intense reaction to something in the interface (or game), but the observer has no idea what it was. By showing the observer what the subject was looking at at the time of the reaction (or usually just before, since there are significant latencies for most physio measures) eyetracking gives the observer a great deal of insight into what the user was responding to and why. Additionally, the real-time nature of these measures means that the observer can pause the session and probe the player to get a subjective response to the stimulus of interest ("hey, it looked like you had something to say about the minimap there, did you have any thoughts to share?"). Alternatively, the observer can just note the circumstances (or save a screenshot) to discuss at the post-session debriefing.

Robert Whelan
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I'm currently working on biometrics testing for electronic slot games. We're using a combination of an Emotiv EEG headset with Mirametrix Eye Tracker recording both fed into iMotion AttentionTool. We tried using a Galvanic Skin Response (Electrodermal Activity) bracelet in conjunction with this, but found that during a typical qualitative session with users, that it took GSR too long to normalise, and that decay rates / recovery time for this was just too long to provide usable data.

Our typical approach to a test session is
1) allow 15 minutes to calibrate the eye tracker and get the EEG headset recording strong signals.
2) allow at least 15 minutes for a user to get into the "flow" (to borrow from Mihály Csíkszentmihályi) of the game. Our games are relatively simple, so this gives sufficient time to gather data. During play we encourage the customer to play as they normally would, and not speak to us.
3) we ask customers what they recalled about the game ( standard qualitative method rather than specifically biometric, but useful nonetheless)
4) we then replay the video (of what's happening on screen), alongside the eye tracking and EEG data back to the user and get them to tell us what they were thinking. They may not always recall, but it helps give some insight. It can also help explain some of the biometric ambiguities - e.g. calm vs bored.

We're at a relatively early stage of using EEG as a test method, but early pilots have suggested that it helps give some useful insight into what a user is thinking / feeling during play.