游戏邦注：本文原作者是游戏研究人员Ben Lewis Evans，他分享了心理生理学研究玩家精神状态的秘决，介绍了脑电描记法、肌电描记术、皮电活动法、心血管测量法、呼吸测量法等几项可行的心理生理学测量方法，分析了它们在测试游戏时存在的优缺点，及其可获取的具有潜在价值的数据资料。

随着游戏研究和测试的发展，评估游戏和游戏性的不同的方法论引起了越来越多的关注。其中之一就是运用心理生理学测量法，例如心率，皮电反应等，来评估玩家的参与度和情绪反应。

本文将讨论目前在心理生理学方面被广泛运用的几个主要的测量法和这些测量法的优缺点，并大体探讨下心理生理学方法的实用性。

什么是心理生理学？

心理生理学是一种通过研究身体提供的信号并借此深入理解什么样的心理生理过程，导致了对应的身体信号或者与身体信号之间存在的联系。

也就是说，这种方法是用人体本身来回答这个问题：“你在想什么？”特别是对游戏研究和测试， 这种方法能有效评估情绪和心理工作负荷。

另外，由于心理生理学为游戏测试和研究人员提供的玩家的数据是不需经由像问卷调查这类的主观的渠道来获得的，一定程度上，显示的玩家反应是公正客观的。

然而，因为心理生理学信号确实经常需要相当多的解读，在游戏测试和研究人员看来，这种方法仍然有待观察。

心理生理学测量法确实拥有的一个大优势在于，它可以检测出可能连玩家自己可能都没有意识到的情绪和身体信号，更重要的是，在无需停止或中断游戏的情况下，能够将这些情绪和身体信号连续不断地自动记录下来。

心理生理学方法测量什么内容？

在讨论这种最流行的心理生理学测量法的详情前，最好先普及下基本的生物背景知识。首先，心理生理学是基于一种认知的观点，这种观点认为人类的认知由整个人体产生。这种认知被称为“具像化的认知”，与其他关于认知的观点相比，这并不是将它与产生思考和情感的心智分离开来。举例来说，具像化的认知即我们的认知和情感由一个广阔的身体反应系统产生，并不是简单地局限于大脑的判断。

换句话说，我们的认知受到我们整个身体的影响，反应于我们的身体上，事实上可以说，它来源于我们的整个身体。现在运用这种心理生理学的方法，你不一定非得认同具像化认知这种观点，但一定要理解这是这一种心理生理学依托的假设。

具体来说，人体拥有一种良好的交流、管理和维持自身运行的方式，它需要通过神经系统来实现。神经系统分成两部分：第一部分是中枢神经系统，它由脑和脊柱最上端组成。这是人体的的“司令部”。因为中枢神经系统被脊椎和颅骨严加防护，因此想要测量里面的运作是相当困难的。

神经系统的另一部分是周围神经系统，它由脊柱发出，负责身体其他部分的日常工作。这意味着从这部分神经系统获取测量值要容易得多，使用最广泛的心理生理学测量法也正是作用在这部分神经系统上。周围神经系统再分成两部分：副交感神经系统和交感神经系统。副交感神经系统处理身体的日常运作和放松；交感神经系统则更多地是负责面临突发情况的反应和兴奋感。

意思就是，周围神经系统可以用于测量情绪。观察典型的情绪二维视图可知，这种方法在测量激励（一般的高活性交感神经活动对抗一般的低活性副交感神经活动）时效果显著，但对于效价（愉悦的情绪对抗不愉的情绪）却并不那么管用。

题外话：情感与情绪

需要指出的是，尽管这二者在日常用语中通常是可互换的，但越来越多的心理学方面的证明得出了这样一种观点：情感和情绪是两种不同的概念。

这种观点称，情绪是身体的状态，我们用心理生理学方法可以探测到。如，计算心率，心率增加则意味着兴奋。然而，情感是情绪状态的意识性感觉。也就是说，情感是你有情绪时才产生的。你可能有情绪，却感觉不到情感，但它仍然以某种方式来影响你的行为。

而就游戏测试层面来说，玩家的情绪是可以通过心率监控器来测量的，但只有当你提供一份调查问卷给玩家时，你才能确定玩家的情感。之前提到过，这意味着你可能可以从心理生理学测量法中得到玩家自己都不一定能够意识到的信息。

特定的心理生理学测量法

脑电描记法（EEG）

在研究中枢神经系统方面，EEG是适用于游戏测试和研发的最简单而有效的工具之一。这是因为它不像高分辨率的PET（正电子扫描）或者fMRI（功能磁共振成像），需要被测量者一动不动地躺在庞大又昂贵（有磁力）的机器上。

EEG的操作是通过在玩家的头上安一个电极来测定大脑产生的电脉冲完成的。

只要让玩家戴上完全电极帽和贴上简易的头带就可以开始执行测量，至少要戴一个小时的电极帽，方可有效测量大脑某区域的特定活动，而头带只负责分析一般的脑电波。

就游戏研究而论， EEG在检测各种不同的大脑活动（或者脑电波）频率等方面，确实是相当可行的参与度与情绪测量法。

大脑活动频率的意义见下：

阿尔法段（8-14赫兹）反映了平静的大脑工作。

贝塔段（14-30赫兹）反映集中，忙碌的大脑工作。

德耳塔段（1-4赫兹）反映睡眠，放松和疲劳。

塞塔段（4-8赫兹）反映激动和震撼。

但是，EEG也存在几个缺点。第一是，其他的测量方法相比，它还是显得较昂贵，特别是购买完全电极帽；脑电图描计器的安装和使用很费时，但对玩家来很有干扰性。例如要安装完全电极帽时，要保证每个电极都得用导电凝胶准确无误地安上，导电凝胶通常还要用针别上，以确保其有较理想的粘贴面。尽管这针不是刺穿皮肤，但还是会使受测者感到难受。据称曾有些受测者甚至在此过程中因极为不适而昏倒。

此外，正如其他测量法一样，EEG一定程度上也易受人为干扰，比如玩家动作太大或者讲话（讲话当然会影响大脑的语言区）。另一点要提的也是所有测量法的普遍缺点，人的心理生理上存在相当大的个体差异，这意味着要不断考虑基线测量值。还有一点对EEG特别重要的是，有些人的大脑在阿尔法段根本不产生任何活动（但在其他方面是正常的）。

最后，解读EEG的测量结果难度较大。比如，如果你探测到德耳塔活动增加了，可能是你的游戏太轻松，因此受测者心情比较愉悦。另一方面，也可能游戏太无聊又累人。同样地，贝塔段活动增加了可能是你的游戏蛮吸引人，或者可能玩家神游了，正在想着他们工作时遇到的让人疲惫的事务。

肌电描记术（EMG）

EMG是一种把电极安到相关肌肉（或者肌群）上来探测肌肉活动的方法。就像EEG（以及大部分测量法），这种方法靠的是测量电流。然而，与EEG不同的是，EMG直接反映的是周围神经系统的活动。

EMG基本上可以用在任何肌肉上——例如，上背部的肌肉群可以反映紧张和压力。但在游戏研究和测试时，通常是用面部肌肉描记术（facial EMG）。把电极放在特定的面部肌肉群上，玩家神情悲伤时，这片面肌群的活动就与消极或积极的情绪反应有关。

准确地说，这些肌肉的位置及对应情绪如下：

眉（皱眉肌）对应消极情绪（不愉快的效价）

面颊（主要是颧肌）对应积极的情绪（愉快的效价）

眼周（轮匝肌）据称是对应快乐和“真正的愉悦”的表情

这使得面肌描计术成为少数几个确实能触及典型双轴情绪视图的效价轴上。此外，面肌描计术具有敏感性，这意味着要是错过了这些肌肉的直接观察，还可以用面部分析软件来弥补。

然而，肌描计术还是存在不足。首先，你仍然必须处理个体差异，所以又得定个基准线（尽管这对能运用其他测量法协助分析的肌描计器来说不是问题）。再者，电极是放在玩家脸上的，还拖着线路，难免存在人为干扰因素。

这可能确实会限制脸部的自然动作，因为这就告诉玩家他们脸上的肌肉正在被记录，玩家自身可能产生不自然的反应—也许在努力帮助你收集数据时会过分强调脸部活动（甚至可能会潜意识地这么做）

最后，可能会产生损坏的记录（或者损坏MP3播放器），在你的数据中一直存在人为干扰的可能性，这可能是由电子干扰或者意外的事件产生的—比如过度的身体动作，或者玩家又讲话了。

皮电活动法（EDA）

皮电活动法也称为皮肤电反应法或者皮肤电传导法。由“electro”这个前缀，可以想到是和皮肤上的电流测量有关，尤其是由于汗腺活动产生的电流变化。

EDA在往往是通过两根手指（或者脚趾）上安装的电极进行记录，它广泛用于测谎测试。由于只需使用两根电极，所以也意味着EDA相对省钱，也比其他心理测量法使用的设备更容易安装。但还是要注意夹着电极的两根指头在记录数据时不能过度移动——如果还要求控制器容易上手，这就显然是个问题了。

EDA测量法看似对情绪激励和心理工作负荷有所反应，并且给出显著的“尖峰”值，这也就是说EDA可以很便利地监测出玩家对游戏中特定活动的反应——不过它的监测也可能在时间上超过平均值。

然而，正如上图所示，在游戏活动发生和EDA作出反应之间还存在一段缓冲时间，通常介于1到5秒钟。EDA在作出下一步反应前还需要一些恢复时间。如果你的游戏中存在大量需检测的活动，

有些可能会被漏掉，并且因为时间延迟，就会难以辨别一个特定的EDA记录的是哪一个活动的反应。此外，EDA是相当敏感和嘈杂的信号，这就意味着它也会带来不少棘手的问题——换句话说，EDA值增加了，可能是因为玩家在说话，动过头，沉浸于游戏中，也可能是正在想你真逗（或者这些全都有）。

心血管测量法

心血管测量法与心脏相关。它主要是观察心脏的节律和节律变化。测量的量值是心率，搏动间隔，心律变化和血压。

前三种测量法都是关于电信号的，都是把电极插在胸部。虽然现在也有许多也可便利使用的心率监控带和高科技T恤，这些是专为运动员设计的（但现在已可在保健商场买到）。

另一方面，血压需要使用(血压计的)橡皮囊细带来测量，这非常像在普通诊断室看医生，与电流测量并无多大关系。

更详尽点，心率就是某个时间段的心跳数（比如一分钟），它会随着工作量的增加和情绪激动而增加。

搏动间隔的测量与心率基本上一样，但它是介于两次跳动之间的时间而言，最初是随着施力增加和情绪激动而减少。这是因为随着心跳次数增加（心率增加），从而介于这些跳动的时间间隔就变短了（所以搏动间隔缩短）。

心率变化由于没有直接测量，所以它会更完整一点，但与搏动时间间隔的变化相当。也就是说，它是由于搏动时间间隔产生的测量值，最初伴随着施力增加和情绪激动而减少。通常情况下，它更能灵敏地测量当工作量改变时的心率变化，而搏动间隔对心率的测量就没那么灵敏，在测量10赫兹频带的情况时尤其如此。

然而，这种方法还是极易受到人为干扰，并且其测量数据源也相当复杂，难以计算。也就是说，如果你在记录搏动间隔时，你还得记录心率变化来扩充你的数据。无论你使用什么设备，都要确保能提供搏动间隔的信息，那些大众市场的训练带并不能达到这个要求。

心血管测量其中一个大优点在于，你可以用肉眼看到心率变量的改变。比如，从休息到完成任务的状态，你可以清楚地看到在搏动间隔之间的心率增加和减少。

最后，血压只是简单地测量血液所处的压力，从而反映心脏的工作强度。血压也会伴随着心绪的激动而增加，但由于它存在的干扰性（游戏邦注：这主要体现在你得用血压计的橡皮囊细带来限制血流量，然后再松开），所以这种测量方法并不是很普遍。

使用心血管测量法还要注意几个要点。首先是上文提到的变化均为初期反应。在经过大约20分钟的工作后，测量结果所出现的趋势，有颠倒的倾向，这是由于身体的自然抵御机制试图返回正常状态所导致的结果。这意味着经过长期的情缴激动或者工作后，心率实际上开始减少，并且搏动间隔增加。如果你没有意识到这种状况，就可能会影响测量数据的准确性。

另外两个问题也在上文其他测量法中已提到，也就是特例和个体差异的问题。一些人可能有特别高或者特别低的心率，或者不规律的心率——当然这个问题还是可以通于比较对应的个体在休息状态下的测量值来解决。

题外话，心血管测量法有时也会让人感到有点压力，受测者可能被测出心率不齐或者高血压，这反映了受测者可能有他们自己都没发觉的潜在心脏问题。你必须要靠自己的判断来处理这个问题，然而，作者的观点是冷静地告诉受测者这可能没什么大不了（有些人只是有心率不齐的特征），同时建议他们去医院做个检查。

最后还有许多可能增加或者减少心血管测量的情况—-是的，可能你的游戏太让人兴奋了，太有挑战性了，但也可能玩家只是深呼吸或者打呵欠（这让心率增加，从而在呼吸中让氧气散布到全身）。人为干扰也是个问题，不用多说，注意，不要有过分的动作或者其他电源造成干扰。

呼吸测量法

最后一种测量法是呼吸作用，它是指呼吸的测量值，这是心血管系统的一部分。之所以将它单独提出是因为它是经常被忽视的测量法，这可能与它不像其测量法那样灵敏有关。但这种测量法操作起来相当简单，也很划算，只需要个呼吸带（或者一件用于测量心脏的高科技T恤也管用）即可。

虽然呼吸带（或者是用于测量心率和搏动间隔的）在皮肤上或胸部上的测量效果最好，呼吸带和心率测量带很容易使用，但一定程度上还是存在着干扰问题，因为受测者必须暴露至少一部分的上身——如果受测玩家是异性的话，这就真成问题了，

然而，因为呼吸作用对诸如EDA、心血管测量法等其他生理测量法具有重大影响，所以呼吸测量法的重要性可见一斑。这意味着如果正在使用其他测量法，为了控制呼吸作用的影响，我们还应该将呼吸作用的情况记录在案。

对游戏来说，工作量对呼吸的一般影响是引起呼吸次数增加。然而，投入游戏或者活动时也会产生玩家憋气的时间，因为这是很自然的准备性动作，是交感神经系统发出“迎战或者撤退”反应的一部分—–玩家在体验特别紧张的游戏时，其呼吸间隔时间可能会比平时更长。

呼吸测量法也不例外，极易受到人为干扰（还是讲话或者动过头），不过因为此法不如其他测量法灵敏，也不是测量电流，所以问题没那么大。

心理生理学测量法折相关问题及益处

作者原本打算再介绍其他测量法，例如记录血皮质醇（一种荷尔蒙），瞳孔扩张，皮肤温度，或者视觉跟踪，但上文的测量法已是心理生理学研究中最普遍使用的方法，因此不再一一赘述。

以下主要总结使用心理生理学测量法的一些问题和益处。

问题

先从与使用心理呼吸测量法相关的问题说起吧。可能有些你已经知道了，但还是值得再提一下。

第一个问题是推断——这与准确理解心理生理学测量法所指含义有关。推论之所以是个问题原因是，大部分认知状态和生理反应之间存在多对一（或者一对多）的关系。

例如，心率增加可能是由许多不同的因素引起的，可能与游戏完全无关。而作为研究者的你，却必须由此推断出心理生理学的量值所传达的信息。

这个问题可以通过心理生理测量法之外的其他辅肋手段来解决。当然，这得和主观的问卷调查结果和客观的游戏用户反馈参数相结合。

又如你发现玩家心率增加，面颊肌电图指数增加，并且问卷调查中的游戏评级指数也在增加，那么你的测量结果就比只用一种测量法的结果更站得住脚了。

然而，一定要避免边说边玩的主观测量法，因为这可能对数据产生干扰。不同测量法相结合有助于通过突显玩家认为比较有意思的战斗，来发现人为干扰因素，但心理生理测量法对此可能没有反应或者仅有消极反应，这可能就会给测量结果带来一些问题。

接下来两个问题是特异性和普遍性。这些因素与推断有关，因为心理生理学测量值对许多不同个体很敏感，而且通过个体，情境，任务和时间产生变化。不是在两者之间定位，而是不断将基准测量值和不同的受测者作比较，以校正个体差异的问题。

然而，更严重的是，这些问题还表明，你在测试环境下看到的结果，可能与在家里安装游戏或者玩你制作的另一款游戏相当不同（即使这款游戏是大量采用了原版游戏机制的继集也难免如此）。

由此可见，正确的推断与使用生理心理学测量方法，对研究游戏玩法与生理反应之间的关系，具有极为重要的作用。

第四个问题有一定益处。这些测量方法擅长检测玩家所承受的工作量和他们的情绪激发。但是面部EMG例外，此法在探测玩家情绪的愉悦感方面并不特别有效。这意味着你可能知道玩家充满激情，但不知道这属于正面还是负面情绪。

最后三个问题是执行成本和人为干扰因素。虽然用于心理生理学测量技术的成本正在降低，但仍然需要借助专门的设备和软件。更重要的是，它需要一定的时间限制，并且要求花大量的时间用于安装设备和分析测量数据。上文曾多次提到，人为干扰因素会介入测量数据——这可能导致数据误差或者隐瞒了真相。

最后，在所提到的所有测量法中，用线路连接和过分动作和说话一样，也算是人为干扰因素。假如无法避免这种情况，那就必须将其记录在案以便控制结果。即使受测者很快适应被线路连接，并且发自内心地配合，但要求受测者的手指保持不动，以便EDA收集数据，这也算是一种人为干扰。

另外，随着时间推移，心理生理学测量法的技术也在进步，干扰性在降低——据作者所称，下一代心率测量传感器不必接触到身体，只需要简单地安置在一张椅子上，就能从坐在该椅子上的人体收集数据。

益处

本文可能看起来有点消极。这主要是因为作者想让读者更清楚，即使这些测量法确实提供了非常客观，可计量的数据，理生理学测量法仍然不算高招。

不过心理生理学测量法仍存在一些益处。首先，它们可以完全自动地，并且还可以连续不断地大量记录数据。这意味着它们可直接与游戏活动的发生关联，不需要你停止和开始游戏，增加游戏量或者等到一切结束才收集数据，这一点确实是超越了众多主观测量法的优势所在。

第二大益处在于，它们能探测玩家的情绪和反应，这些情绪和反应玩家自身可能无法当即意识到（或者在玩家意识以前探查到）。特别是如果玩家不能准确地表达为什么他们不喜欢或者喜欢某个游戏特点，这些测量法就大有帮助了。

最后还是要问一句，玩家是否没有意识到这些情绪可能影响他们的行为和游戏的乐趣？虽然越来越多的心理学研究确实暗示，无意识的身体状态（情绪）对人的行为会产生有意义的影响，但目前为止这一点仍然有待考证。（本文为游戏邦/gamerboom.com编译，转载请注明来源：游戏邦）

Game Testing And Research: The Body And The Mind

[A researcher shares the secrets of psychophysiological research into players' mental states, outlining several possible techniques and both the pitfalls and potential data that can be gained from applying these in a game test environment.]

As game research and testing develops, there has been an increasing interest different methodologies for assessing games and gameplay. One such area is the use of psychophysiological measures, such as heart rate or electrodermal activity, to assess players’ engagement and emotional response.

This article will discuss several of the main measures currently widely used in psychophysiology and their advantages and disadvantages as well as a general discussion of the usefulness of psychophysiological measures.

What is Psychophysiology?

Psychophysiology is a method for studying the signals provided by the body in an attempt to gain insight and understanding into what psychological processes are underlying or related to those body signals.

In other words. it is using the human body to answer the question “Whatcha thinkin’?” In particular for game research and testing, it can be useful for assessing

emotion and mental workload.

Also, since psychophysiology offers game testers and researchers access to data from players without having to go through subjective channels, such as those provided by questionnaires, it also offers a somewhat unbiased assessment of player reactions.

However, since psychophysiology signals do often require quite a bit of interpretation, there is still plenty of room for observation (interpretation) bias on the game tester or researchers’ behalf.

One big advantage that psychophysiological measures do have is that they offer access to emotions and body signals that players themselves may be unaware of, and what’s more, they can be recorded automatically and continuously without stopping or pausing gameplay.

What Does Psychophysiology Measure?

Before getting into the specifics of the most popular psychological measurements, it is important to quickly cover some basic biological ground. First of all, psychophysiology relies on a view of cognition that asserts human cognition as arising from the whole body. This is called “embodied cognition”, and compared to alternate views of cognition, does not propose some kind of separate “mind” where thinking and feeling occurs. Embodied cognition, rather, assumes that our cognitions and feelings arise from a wide system of bodily reactions, and are not simply confined to our brain, for example.

In other words, our cognition is affected by, reflected in, and in fact arises out of our whole body. Now, to use psychophysiological methods you do not necessarily have to buy into this view of embodied cognition, but it is necessary to understand that this is the assumption from which psychophysiology hangs.

Given a view of cognition as embodied, it is important that the body has a good way to communicate, manage and maintain itself. This is handled through the nervous system, which can be split into two parts; the first is the central nervous system, made up of the brain and the very top of the spine. This is the executive control system of the body. As such it is well-protected, and quite difficult to access if you want to measure what is going on in there.

The CNS is much easier to access if you are a demigod.

The other part of the nervous system, the peripheral nervous system, comes out from the spine and handles the day-to-day running of the rest of the body. This means it

is much easier for us to access and get measurements of, and it is with this system that most widely-used psychophysiological measures interact. The peripheral nervous

system is in turn split into two parts: the parasympathetic system, which handles the general maintenance of the body and relaxation, and the sympathetic system, which is more for handling emergency reactions and excitement.

This means that the peripheral nervous system can be used to measure emotion. In particular, given the typical two-dimension view of emotion, it is particularly useful for measuring Arousal (High, generally sympathetic activity versus Low, generally parasympathetic activity) but is less useful when it comes to Valence (Pleasant emotions versus Unpleasant emotions).

An Aside: Feelings and Emotions

As an aside, it is worth noting that there is a growing body of evidence in psychology that has lead to a view of feelings and emotions as two different things, despite their generally interchangeable use in everyday language.

This view states that emotions are the body states we have that psychophysiology can detect, for example an increased heart rate meaning excitement, whereas feelings are the conscious perception of the emotional states. That is to say, feelings are when you feel an emotion. The upshot of this is that it may be possible to have an emotion, but not feel it — yet still have it affect your behavior in some way.

Or to put it in terms of game testing, a player’s emotion can be measured through the heart rate monitor, but only when you provide them with a questionnaire (or

another subjective measure) can you be sure that you are tapping what that player feels. As mentioned earlier, this means that you may be able to get information from psychophysiology that players themselves do not necessarily consciously have access to.

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).

Cardiovascular measurement

Cardiovascular measures are related to your heart, and are mainly about looking at rhythms and how they change. These measures are heart rate, inter beat interval, heart rate variability, and blood pressure.

Canada Game Conference

The first three measurements are again all about measuring an electrical signal, and are measured by attaching electrodes to the chest. Although nowadays there are many heart rate monitoring belts and high-techT-shirts which are designed for athletes (available the commercial fitness market) which can easily be used as well.

Blood pressure on the other hand requires a cuff to measure, much like at your doctor’s office, and does not involve a measurement of electric current.

To go into a bit more detail, heart rate is the number of heat beats you have per unit of time (say per minute), and this will typically initially increase with increased workload and emotional arousal.

Inter beat interval is basically the same measure as heart rate, but refers to the time between beats and therefore tends to initially decrease with increased effort and emotional arousal. This is because there are more beats (heart rate is increasing) therefore the time that passes between those beats is shorter (so inter beat interval decreases).

With relatively cheap and easy heart rate measurement in every sporting goods store and gym, we have come a long way from this (image from Wikipedia).

Heart rate variability is a little more completed in that it is not measured directly, but is rather the variability of the inter beat interval. In other words, it is derived from measurements of inter beat interval over time. This again initially decreases with increased effort and emotional arousal and it is generally seen as a more sensitive measure to changes in workload than inter beat interval and heart rate — especially if the 10hz frequency band is examined.

However, it is also quite vulnerable to any artifacts in the underlying data source, and can be relatively complex to calculate. That said, if you are recording inter beat interval then you should also attempt to calculate heart rate variability as it increases the richness of your data. It is therefore important that whatever device you use does provide you with information on inter beat interval, something that some of the mass market exercise belts do not do.

One of the great things about cardiovascular measures is that you can often see changes in variables with the naked eye. For example here you can clearly see an increase in heart rate and a decrease in inter beat interval when moving from a resting to a task completion state.

The change in heart rate and inter beat interval can be clearly seen when the task begins.

Finally, blood pressure simply measures the pressure that your blood is under, and therefore how hard your heart is working. This also initially increases with arousal but it is a less common measurement due it is intrusiveness in that you need to have a cuff to restrict blood flow, and then release it again.

There are of course some caveats to using cardiovascular measures. The first is that I have said that the changes above are initial reactions. This is because after about 20 minutes or so on a task, the trends I have described above tend to reverse due to the body’s natural defense mechanisms attempting to return the body state to normal. This means that after long periods of emotional arousal or workload, heart rate actually starts to decrease and inter beat interval increases. This can cause problems with your data if you are not aware of it.

The other two problems are ones I have mentioned previously with other measures, and they are of specificity and individual differences. Some people may have particularly high or low natural heart rates, or irregular rhythms — again this can be overcome through the use of individual resting measurements which are then used as comparison points for each individual.

As an aside, cardiovascular measures can also sometimes get you in a bit of a stressful situation, where you may detect irregular rhythms or particularly high blood pressure in your participants which may indicate underlying heart problems that they themselves may not be aware of. You have to use your own judgment when dealing with this. However, I would personally lean towards calmly advising any such participant that it is probably nothing (some people just have irregular patterns) but suggesting that they may want to have a checkup at their doctor’s office.

Finally there are many things that can increase or decrease cardiovascular measures — yes, perhaps your game is really exciting and demanding at his exact moment, but it is also possible that your player just took a deep breath or yawned (which causes your heart rate to increase as to distribute the oxygen in that breath around the body). Artifacts are also a problem, so again, no talking, and be careful that there isn’t interference from excessive moment or other electrical sources.

Respiration

The final measure I want to discuss is respiration. Respiration refers to the measurement of breathing, and is actually part of the cardiovascular system. However, I want to mention it separately because it is an often-overlooked metric. This is probably due the fact that it is not as sensitive as some of the others mentioned here.

However, it is relatively easy and cheap to measure, requiring only a respiration belt (or one of the high-tech T-shirts used to measure information from the heart will also work).

Although it should be noted that respiration belts (and the belts used to measure heart rate and inter beat interval) work best when next to your skin on your chest.

Therefore, even though respiration belts and heart rate measuring belts are easy to use, they are somewhat intrusive in terms of people often having to show experimenters at least part of their bare upper bodies – a situation can particularly be an issue if the player being tested is of the opposite sex to the tester.

However, respiration is also important to measure because breathing has a strong effect on other physiological measure such as EDA and the cardiovascular measures.

This means that if these other measures are being used then respiration should also be recorded, if only to control for its effect.

In terms of gaming, the general effect of workload on respiration is to cause an increase in respiration. However engagement in a game or activity can also cause periods where players breath is held as this is a natural preparatory action as part of the “fight or flight” response setup by the sympathetic nervous system — certainly an ex-girlfriend of mine used to shout at me to “remember to breathe!” whenever I would play particularly tense games.

Respiration is of course also vulnerable to artifacts (again no talking or excessive movement) although because it is not as sensitive as other measures, and is not measuring an electrical current, this somewhat less of a problem.

Issues Related to, And Benefits of, Using Psychophysiological Measures

There are of other measures I could have covered, such as recording blood cortisol, pupil dilation, skin temperature, or eye tracking, but the measures I have covered are probably some of the most common ones used in psychophysiological research. Finally, though, I would like to just wrap up by summarizing the benefits and issues related to the use of psychophysiological measures.

Issues

Because I don’t want to end on too much of a down note, I will start with the issues related to the use of psychophysiological measures. There are a few of these, and you may have picked them up already but they are worth repeating.

The first is problem of inference — this is related to working out exactly what the psychophysiological measurement you have taken actually means. This is problematic because there is a many-to-one (or one-to-many) relationship between most cognitive states and physiological responses.

In other words, an increase in heart rate, for example, can be caused by many different factors and may not be related to gameplay experience at all. The upshot of this is that you, as the researcher, must infer what a psychophysiological measurement means.

This problem can be somewhat overcome by not using psychophysiological measurements in isolation. Rather, they should be used alongside subjective questionnaires and objective game data metrics.

For example, if you find an increase in heart rate, an increase in facial EMG in the cheeks, and an increase in ratings of fun on the Game Evaluation Questionnaire in response to your game mechanic, then you are on much stronger ground than if you had just one of those measures.

However, talk-as-you-play type subjective measures should obviously be avoided as they will produce artifacts in your data. This combination of measures also helps with detection of artifacts, by highlighting conflicts where players may be reporting that they are having fun, but psychological measures may not be reacting or are negative, which could indicate a potential measurement problem.

The next two issues are those of specificity and generality. These factors are related to inference, in that psychophysiological measurements are sensitive to many different things, but also change across individuals, situations, tasks and times. Always taking baseline measurements and comparing within subjects, rather than between, can address the problem with individual differences.

However, more seriously, these issues also potentially mean that the results you see in your test environment may be quite different in a home gaming setup or for the next game you make (even if it is a sequel to your last one that uses many of the same mechanics).

Again, this raises the importance of correct inference and the use of psychophysiological measures to compliment other subjective and objective measurements. Also as research in psychophysiology and games advances its possible that the connection between certain gameplay elements and certain reactions in physiology may become clearer.

The fourth issue is also somewhat of a benefit. This is that many psychological measures are good at detecting the workload a player is under, and their emotional arousal. But, with the exception of facial EMG, they are not particularly useful for detecting the pleasantness of a player’s emotion (valence). This means that you may know that your players are experiencing an intense emotion, but not know if that is a good thing or not.

The final three issues are that of expense, artefacts, and intrusiveness. While the price of much of the technology used to measure psychophysiology is decreasing, it does still typically require specialized equipment and software, and perhaps more seriously given the time limits that often exist in game development can also cost a lot of time to both setup and analyze. Furthermore as mentioned many times above there is always the potential for artifacts in your data — which could lead to your data being biased or the masking of useful effects.

Finally wiring someone up is a somewhat intrusive thing to do and with all of the measures mentioned above extensive movement and talking should be avoided as they produce artifacts. Or if they cannot be avoided, they need to be noted down and recorded in order to be controlled for. Being asked to hold your fingers still if so EDA can be collected is also intrusive in its own way, although thankfully people do quite quickly adapt to being wired up and can often put it pretty much out of their mind.

Also, as time goes on, the technology for measuring psychophysiology is also advancing and its intrusiveness is decreasing — for example I have heard talk of next generation heart rate measuring sensors that do not have to be attached to the body and can simply be placed in a chair to collect data from anyone who sits down.

Benefits

This article may seem a little too negative. This is mainly because I want to make it clear to anyone reading that psychophysiological methods are not a silver bullet, even if they do provide nice objective quantifiable data.

However, to finish up, I would like to again note some of the main benefits of psychophysiological methods. First of all, psychophysiological measures can be fully automated in terms of their recording, and can also be pretty much recorded continuously. This means they can be directly related to gameplay events as they happen.

This is quite a big advantage over many subjective measures that require you to either stop and start a play experience, add additional load to a gameplay experience,

or wait until the end before you can collect data.

Secondly, the other big benefit of psychophysiological measures is that they detect emotions or reactions in players that they themselves may not be aware are present (or detect them before they enter awareness). This can be a great help, especially if players are having problems expressing exactly why they dislike or like a particular feature.

Although, it must be also asked, if players are unaware of these emotions then can they influence their behaviour and their enjoyment of the game? The science around this is currently unclear, although there is a growing body of psychological research that does suggest that unconscious body states (emotions) can have a meaningful impact on human behavior.（source:gamasutra）