Bachelor Thesis

Digital Game Development

Thesis no: TA-2013:07

06 2013

Exploring Need-based AI Behaviour

and its E↵ect on the Game

Experience of Neverwinter Nights

Gunnar Sodergren

School of Computing

Blekinge Institute of Technology

SE-371 79 Karlskrona

Sweden

This thesis is submitted to the School of Computing at Blekinge Institute of Technology in

partial fulfillment of the requirements for the degree of Bachelor of Science in Digital Game

Development. The thesis is equivalent to 10 weeks of full time studies.

Contact Information:

Author:Gunnar Sodergren 870517E-mail: gunnar.sodergren@gmail.com

University advisors:Olle HilbornJohan HagelbackSchool of Computing

School of ComputingBlekinge Institute of Technology Internet : www.bth.se/comSE-371 79 Karlskrona Phone : +46 455 38 50 00Sweden Fax : +46 455 38 50 57

Abstract

Single Player Roleplaying Game (SPRPG) is a populargenre among players as well as developers, with recentblockbuster titles such as Skyrim by Bethesda and MassE↵ect 3 by Bioware. In recent years, an occurrence thathave been gaining a lot of attention is the development ofmore advanced and vivid Artificial Intelligence (AI) withinthese SPRPG and a lot of progress has been made towardsmaking the Non-player Character (NPC) more vivaciousand life-like.

It is, however, still a common occurrence that NPCswait around for the player to interact with them; never hav-ing a plan or agenda of their own. Their purpose seem tobe to wait for the player and provide him or her with infor-mation, bartering or a quest. This could result in a gameenvironment that feels static and lifeless to some playersand, thus, possibly become detrimental to the game expe-rience.

The main objective of this thesis was to implement aneed-based system, resembling, to some degree, the oneused in The Sims by Maxis, where NPCs get hungry, thirsty,sleepy and similar, and to test whether this system will en-hance the game experience. If the NPCs of a SPRPG haveneeds of their own and therefore can not just wait aroundfor the player to come to them, it may make the gameexperience more life-like and dynamic.

A need-based system that allows the designer to definea set of needs for each NPC, was implemented using theAurora Toolset for Neverwinter Nights by Bioware. Thesystem was then tested by allowing a number of peopleplay a custom module for Neverwinter Nights twice: oncewith the system in place and once without, then answeringquestionnaires regarding their experience.

The results show, unanimously, that this prototype didenhance the game experience. Though this was a smallmodule and only a prototype, it does indicates that the useof a need-based system might indeed enhance the dynamicand vivacity of a SPRPG.

Keywords: Artificial Intelligence, Neverwinter Nights, Non-player Characters

i

Acknowledgement

A great thanks to my University advisors, without whom this thesis would neverhave been completed on time:

Olle Hilborn, for his patience, great advise and keen grasp of the mysteries ofstatistics.

Johan Hagelback, for his highly appreciated feedback and many advise re-garding implementation and design.

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List of Figures

2.1 Maslows Hierarchy of Needs from [6] . . . . . . . . . . . . . . . . 5

5.1 How to complete the first quest of the module. Both player andNPC must be in the big blue square to progress in the quest. Thedotted red line indicates that an NPC may go straight to attendinga primary need. Plott, Thal and Merem are the names of theNPCs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.2 Thals, one of the NPCs within the module, movement with needsimplemented. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

A.1 The Postplay Questionnaire filled out after having played bothmodules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

A.2 The Module Questionnaire to be filled out after having played eachmodule. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

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List of Tables

5.1 NPCs in the module, their function and their needs. PF:Factor bywhich the primary needs are increased. SF:Factor by which thesecondary needs are increased. . . . . . . . . . . . . . . . . . . . . 11

5.2 Example of a need (Hunger), its triggers and what they trigger forthe NPC Thal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

6.1 Dimensions and their related statements . . . . . . . . . . . . . . 156.2 The means, SDs and p-value of each module for every dimension,

for all twenty-four test subjects, disregarding the order in whichthe modules were played. . . . . . . . . . . . . . . . . . . . . . . 16

6.3 Questions related to third dimension. . . . . . . . . . . . . . . . 176.4 Questions related to fourth dimension. . . . . . . . . . . . . . . . 17

A.1 The means and SDs of each module for every construct, for thetwelve test subjects that played Module Normal first. . . . . . . 24

A.2 The means and SDs of each module for every construct, for thetwelve test subjects that played Module Need first. . . . . . . . . 24

A.3 Questions from A.1 translated to English . . . . . . . . . . . . . . 24A.4 Questions from A.2 translated to English . . . . . . . . . . . . . . 27

iv

Contents

Abstract i

1 Introduction 1

1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Research Question . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Background 3

3 Related Work 6

4 Method 7

5 Approach 8

5.1 Theoretical Layout . . . . . . . . . . . . . . . . . . . . . . . . . . 85.2 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.3 Testing Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5.3.1 Dynamic and Life-like NPCs . . . . . . . . . . . . . . . . . 125.3.2 Change in NPC Behavior . . . . . . . . . . . . . . . . . . 135.3.3 Engaging Experience . . . . . . . . . . . . . . . . . . . . . 135.3.4 Elusive NPCs . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.4 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6 Results 15

6.1 Dynamic and life-like NPCs . . . . . . . . . . . . . . . . . . . . . 156.2 Change in NPC Behaviour . . . . . . . . . . . . . . . . . . . . . . 166.3 Engaging Experience . . . . . . . . . . . . . . . . . . . . . . . . . 166.4 Elusive NPCs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

7 Discussion & Conclusion 18

7.1 Dynamic and life-like NPCs . . . . . . . . . . . . . . . . . . . . . 187.2 Change in NPC behavior . . . . . . . . . . . . . . . . . . . . . . . 197.3 The game o↵ered an engaging experience . . . . . . . . . . . . . . 197.4 The game seemed unusual and strange . . . . . . . . . . . . . . . 207.5 The characters acted in a confusing way . . . . . . . . . . . . . . 20

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7.6 The NPCs were hard to find and to follow . . . . . . . . . . . . . 207.7 Final Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8 Future work 22

References 23

A Appendix 24

vi

Chapter 1

Introduction

The Roleplaying Game (RPG) genre spans a vast variety of sub-categories, eachwith its own distinct features and hooks. RPGs do, however, have commonfeatures that make them such. They usually involve some form of leveling up,where the main character progress in skills and power, it usually takes placewithin a fictional setting [10][1]. Single Player Roleplaying Game (SPRPG)sare roleplaying games that are played alone, unlike Massively Multiplayer OnlineRoleplaying Game (MMORPG) such as World of Warcraft by Activision Blizzard.

A lot of what is discussed in this thesis could be applied to many types ofRPGs, such as MMORPGs. However, throughout this thesis the RPGs referred toare, unless anything else is stated, SPRPGs. The potential enjoyment of a SPRPGcan be determined and described by many factors, where the vivacity and dynamicof the Artificial Intelligence (AI) that controls the Non-player Character (NPC),is one of them.

A few older games, such as Ultima VI by Origin Systems (1990) and SuikodenII by Konami (1998), has made use of scheduled events, where NPCs go to sleepat night, allowing players to, for instance, steal items and gear from their storeand only find certain NPCs certain times of the day.

More recent games, for example Skyrim by Bethesda, also uses similar systemsto create more dynamic NPCs by having shop-keepers close their stores at night,guards only patrolling certain areas during certain times of day, thus potentiallymaking the environment more dynamic and vivid.

These features, and similar ones in other games, certainly work toward en-hancing the vivacity, and potentially the enjoyment of a game. However, theyare usually timed events, based more on time of day rather than the actual needor desire of the single NPC. This can make the system quite predictable, whichcould make the experience feel static and lifeless, since the events are repeatedevery day, hour or whatever time trigger has been set in place.

This thesis revolve around the design and implementation of a need-based AIsystem for use in SPRPG and the exploration of whether it actually enhances thegame experience for the player, with regards to dynamic and vivacity.

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Chapter 1. Introduction 2

1.1 Motivation

While many attempts to create more vivid and life-like NPCs in SPRPGs havecertainly been made, it is still a common occurrence that NPCs, be it quest-givers,vendors or simply citizens of one city or another, stand around throughout theentire game and wait for the player to show up and interact with them. This isa convenient solution, as it gives the player no doubt or hesitation as to when orwhere he or she will be able to complete a quest, buy gear or whatever his or hercurrent goal might be. It does, however, increase the risk of making the gameenvironment feel lifeless and static and thus become a potentially detrimentalfactor to the game experience.

If a quest-giver simply stands around all day, never having to grab a biteto eat, never needing any sleep and never needing to do anything but wait forthe player to come up and talk to him or her, the environment could feel staticand quite unrealistic. This could result in a game environment that is likely toimmerse the player, since realistic and believable NPCs are part of the narrativeand the storyline of the game [12].

1.2 Research Question

Will the design and implementation of a need-based system within NeverwinterNights enhance the gameplay experience with regards to dynamic and vivacity ofthe NPCs?

Chapter 2

Background

AI is said to be the study and engineering of making machines behave what can beconsidered intelligently [5]. AI covers a wide variety of fields and sub-disciplineswithin computer science: from expert systems that use a knowledge base andautomated reasoning in order to answer questions and queries the same way ahuman expert would, to flocking behaviour which attempts to mimic the movepatterns of fish, birds or similar [9].

AI in digital games have made good use of many of these disciplines whenit has fit the problem at hand, with varying success. However, where a lot ofmainstream AI pursue the optimal solution to a problem or strive to simulatehuman cognition, game AI is all about fun [13]. On the subject of defininggame AI, Rabin [9] stated the following: ”Game AI is anything that a gameAI programmer will have to program in order to make game characters appearintelligent. The AI in a game must not only think, but also must sense itsenvironment and act convincingly within it”.

AI in Digital Games have existed almost as long as video games themselvesand has always been a component to what makes up a game AI [9]. As early as1980, in the classic PacMan by Namco, AI was presented to govern the ghosts thatchased the avatar around the level. Two of the ghosts followed the avatar, tryingto catch him, always moving towards his current position and taking the routethat was calculated to be shortest. The other two randomized their movementsaccording to a deterministic randomizer, thus becoming fairly unpredictable [7].Once the player picked up the famous power-up, which allowed him to eat theghosts, the behaviour was reversed and the ghosts tried to move as far awayfrom the avatar as possible. A highly simplistic AI system, but one that did itsjob very well, given the gameplay environment. Game AI is often about findingand implementing the easiest solution to a problem to create intelligent behavior,rather than actually making the NPCs intelligent [11].

It has, however, not always been regarded as very important and thereforelittle e↵ort and research has been put in to it, especially in the early days ofdigital game development. Because of this, Artificial Intelligence in games waslong looked upon with a certain amount of skepticism, from game developers aswell as researchers in what is known as Academic AI [13].

3

Chapter 2. Background 4

In the last decade, with increasing demands from the players, game AI hasbeen given a lot more focus and is becoming richer, more entertaining and complexthan the AI of the past [13]. Titles such as Battlefield by Dice, Dragon Age:Origins by Bioware and The Sims by Maxis exemplifies how life-like and vivid AIis essential to the gameplay experience [9].

In real-time strategy games the main challenge is to o↵er an appropriate chal-lenge level to all players, regardless of their experience. With the use of cleverlyhidden cheats and the use of AI technologies, such as flocking behaviour, thetactical reasoning and deployment has become quite advanced and AI bots cannowadays often provide a challenge even for highly experience players.

In first-person shooters, enemies have long been quite good at aiming andshooting, but a lot worse at using tactics and strategic reasoning. However, thegames of today, such as Battlefield 3 by Dice, o↵er AI agents that seem to think,reason and employ tactical deployment when engaging the players.

When it comes to AI in SPRPG, an imbalance seem to be present, regardingthe NPCs and their behaviour. The combat part of the AI in these games are oftenquite advanced, with challenging enemies and, depending of the game, engagingcombat scenarios. For other NPCs such as vendors and quest-givers, the vivacityis however often lacking [3]. Quest-givers often just stand in one place and waitfor the player to come and interact with them, vendors rarely close shop, andwhen they do it is because of a timed event rather than anything else, and otherNPCs are almost always available with whatever tip, information or training theymight provide.

NPC systems that are based on the needs and desires of the NPC rather thanon schedule are not particularly common in digital games, and certainly not inSPRPGs. They are, however, present in simulation games such as The Sims byMaxis (see chapter 3) and Rollercoaster Tycoon.

When talking about need-based systems, and how the human needs and de-sires actually function, there are many di↵erent factors to consider and approachesto take. One such approach is presented in Maslows Hierarchy of Needs [4].Maslows Hierarchy of Needs defines, as the name implies, a person’s di↵erentneeds on a hierarchal pyramid; from primary to quinary (see Figure 2.1). Thefirst level represent the physiological needs; hunger, sleep, sex, excretion andsuch, the secondary represents safety needs such as health and employment secu-rity and so on until the quinary level that represents self-actualization needs suchas creativity and problem-solving (see Figure 2.1).

It is stated, within the concept of Maslows Hierarchy of Needs, that the sec-ondary needs cannot be satisfied until the primary need are fulfilled, the tertiarynot until the secondary ones are and so forth. For a need-based system withinSPRPGs, this concept could be used to inspire the priority in which the NPCshandle their various needs. The need-based system proposed strives to be life-likeand by using inspiration from Maslows Hierarchy of Needs, a model that attemptsto describe the actual human needs, the structure of the system can be designed

Chapter 2. Background 5

Figure 2.1: Maslows Hierarchy of Needs from [6]

quite easily. Maslows Hierarchy of Needs also provides a clear structure of howneeds are prioritized, which is an important feature of the need-based system.

Chapter 3

Related Work

While recent games, such as Skyrim by Bethesda has indeed introduced an at-tempt to make the NPCs of a SPRPG more life-like and vivid, these system arebased on timed events and does not really simulate a behavior or need of a specificNPC.

Simulation games, such as The Sims 3, does indeed simulate the needs a thecharacter, or ”sim”, where character become hungry, sleepy, thirsty and similar.

The Sims 3 by Maxis, which is a reality-simulation game in which the playertakes control over one or more avatars and help guide them through their dailylife, simulate the needs that the sims might have, such as hunger, sleepiness andthirst. The characters also do what they can to satisfy their need by exploring,and then remembering, where their needs can be satisfied.

Related works to this thesis include the study of emergent psychosocial be-havior by Bailey and Katchabaw [2], where the NPCs, through a system thatuses mechanics such as designer-defined psychological and social concepts, showemergent and, to some degree, unpredicted behaviour. This may enhance the ex-perience of vivacity and life-like gameplay within a game environment and thus,potentially, enhancing the overall experience of the game.

The creation of reactive AI NPCs by Gruenwoldt and Katchabaw [3], by mak-ing use of and manipulating an underlying relationship system that binds NPCsand objects together, thus making NPCs and, potentially, the game environmentmore life-like and vivid. This may, in turn, provide a richer and more dynamicgame environment.

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Chapter 4

Method

The research question to be answered in this thesis is:Will the design and implementation of a need-based system within NeverwinterNights enhance the gameplay experience with regards to dynamic and vivacity ofthe NPCs?

The focus of this thesis is to design, implement and test a need-based systemwithin the established environment of Neverwinter Nights. The purpose is to de-termine whether the implementation of such a system will enhance the gameplayexperience regarding dynamic, vivacity and the feeling of life-like NPCs.

The outcome and result of the need-based system will therefore be generatedthrough empirical study using an experiment where test subjects will test twomodules: one with the need-based system and one without. After having testedeach module, the test subjects will be given questionnaires relating to their ex-perience.

The questionnaires are designed to yield quantitative results, giving exactanswers to the questions. A qualitative approach may have yielded more infor-mation from each test subject, with more nuances, but would most likely also bemore biased as each test subject would provide his/her own set of information.By giving each test subject the same questionnaire and the same information,any potential bias will be eliminated and the results will be easy to quantify.

The sample used for the experiment, 24 game development students, wereselectively chosen, since they are likely to have good insight in both gamingand game development. Thus, any results generated are subject to this specificpopulation; game developers and potentially avid gamers. Though a good sampleto design for, it could potentially eliminate a lot of other players. A few of the testsubjects were also aware of the purpose of the study before doing the experiment,having inadvertently heard about it, which could influence the results.

The results from the 24 test subjects are analyzed using statistical tests, suchas Wilcoxon signed rank test and paired samples t-tests.

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Chapter 5

Approach

The implementation is an attempt to create a system which will help increase thevivacity of the NPCs within a given SPRPG.

As discussed earlier, NPCs in SPRPGs often feel lifeless and static. Onereason for which could be that they do not have needs and desire of their own.The implementation was a prototype for a need-based system which allowed thedesigner to add a unique set of needs for each NPC, making each NPC wantdi↵erent things and, by varying how fast a need grows, at di↵erent times.

5.1 Theoretical Layout

The system proposed here is based upon Maslows Hierarchy of Needs[4] (seeBackground). Whether or not that hierarchy is truly how the human needs work,make little di↵erence since the purpose of this system is to make NPCs morelife-like and the game environment more vivid.

As with Maslows hierarchy of needs, the needs present in this system arearranged in a hierarchal manner and each level of needs must be attended beforethe next one (i.e. primary before secondary, secondary before tertiary and soforth).

The implementation created for this thesis allows for two levels of needs;primary and secondary. The primary needs are intended to correspond to aperson’s most basic needs: the ones he or she need to satisfy in order to survive.Hunger, thirst and sleep are examples of such primary needs. The secondaryneeds correspond to every other need, addiction or desire a person might have.It could be lust, the need for intimacy, the need for alcohol or tobacco to satisfyan addiction or simply a very strong desire to do something. A rule of thumbfor this system is that if failure to satisfy a certain need could result in sicknessor even death, it is to be considered a primary need. All other needs, urges anddesires, though potentially quite strong, can be considered secondary.

While any primary need is stronger than the secondary ones, no secondaryneed is attended to, e.g. if the current hunger value is higher than, for instance,the smoking value and the kleptomania value, the hunger must be dealt withbefore the NPC is allowed to go smoking or stealing.

8

Chapter 5. Approach 9

Figure 5.1: How to complete the first quest of the module. Both player and NPCmust be in the big blue square to progress in the quest. The dotted red line indicatesthat an NPC may go straight to attending a primary need. Plott, Thal and Merem arethe names of the NPCs.

Chapter 5. Approach 10

Whenever a need is not satisfied, the NPCs may react di↵erently when inter-acting with the player. A hungry quest-giver may be irritated, cranky or other-wise unpleasant while speaking to the player; a sleepy vendor may be less likelyto notice that the player is picking his or her pockets or even that the player hasapproached him or her; a quest-giver with a severe case of, say, agoraphobia (thefear of open spaces), may insist that the player meet him or her inside, possiblymaking the e↵ort to get to him or her challenging, and so on.

Along with the many potential interaction-related e↵ects this system provides,it also adds an element of predictable unpredictability to the NPCs behaviour.For example, you can not at a given time be sure where a NPC is, but you knowto look in the tavern, the brothel or the casino (see Figure 5.1). While he orshe is attending to a need, be it hunger, sleepiness or nymphomania (a form ofsex addiction), the NPC is obviously occupied elsewhere and may not be easilyfound: at least not as easy as if he or she is just standing in the same place dayin and day out.

Each need is based upon a value ranging from 0 to 100, where a value 0corresponds to a fully satisfied need and a value of 100 means that the need isextremely urgent. In the case of hunger a 0 would mean a belly full of food and avalue of 100 would correspond to being on the verge of passing out from hunger.As the need becomes more urgent, the value increases and triggers, at predefinedvalue, di↵erent behavior and actions.

The tool used for the implementation of this system was the Aurora Toolset forNeverwinter Nights™ by Bioware™. The Aurora Toolset is a powerful prototypingtool that allows manipulation of almost every aspect of the Neverwinter Nightsgame. This, along with the benefits of testing a new system within an alreadyestablished environment, was the reason it was chosen for this prototype.

5.2 Implementation

To ensure that the system could be tested quickly and without having to play fora long time, the environment was created to contain only three missions for theplayer to carry out and only half a dozen of NPCs to interact with.

Each NPC, whether quest-giver, vendor or simply a source of information,was given one primary need, in this case Hunger, and one or two secondary onesthat were di↵erent on each NPC (see Table 5.1). Examples include Kleptomaniaand Lust.

The Neverwinter Nights engine uses a feature called ”heartbeat”, which func-tions as a update trigger for each character, monster, NPCs and object withinthe game. Using this heartbeat function, each need could be implemented torise slightly according to a set factor, depending on current need and NPC (seeTable 5.1). The factors PF and SF are the factors with which the Primary andSecondary needs are increased.

Chapter 5. Approach 11

Name Function Primary Need Secondary Needs PF SFNicha Informant/Quest-receiver Hunger Lust/Gambling 1.0 1.0Plott Quest-giver Hunger Drinking/Sleep 1.8 0.7Elorfin Quest-giver Hunger Gambling 1.0 1.0Merem Quest-receiver Hunger Kleptomania/Smoking 1.0 1.0Thal Quest-giver/Vendor Hunger Lust 1.0 1.0

Table 5.1: NPCs in the module, their function and their needs. PF:Factor by whichthe primary needs are increased. SF:Factor by which the secondary needs are increased.

Each NPC, and each need within that NPC, was then given a set of triggersthat were set to go o↵ whenever the current need reached a certain level. Forexample, when the value of Hunger reached above twenty, a trigger related toHunger would be set o↵ (see Figure 5.2). The triggers was chosen based on trialand error, with the limit that the maximum value was 100 and the minimum was0.

Trigger Action taken20 Conversation change: becomes irritated ands that player hurries with quest40 Conversation change: becomes more irritated and must be convinced to discuss quest50 Starts walking to tavern, but can still be talked to about quest75 Runs to tavern, refuses to discuss quest

Table 5.2: Example of a need (Hunger), its triggers and what they trigger for theNPC Thal.

Once all needs, primary and secondary, have been increased and the corre-spondent triggers activated, a weighted comparison is made to ensure that themost urgent need is attended to. No secondary need is allowed to be attended towhile any primary need is either higher than the secondary need or high enoughto become dangerous (i.e. close to killing or harming the NPC).

Should a trigger be set o↵ that requires the NPC to attend to the need, theappropriate action will be taken (e.g. if the highest need is hunger, the NPCwill go to the tavern to grab a bite), otherwise he or she will remain posted andcontinue to provide whatever service he or she might give the player. However,not all triggers result in an action be taken; some triggers merely change thecurrent behavior of the NPC. This could, as mentioned above, result in a varietyof things. The NPC becoming agitated, angry, flirty or otherwise changing theway they interact with the player.

Once a need is attended to, the value of that need is decreased, dependingon how, where and for how long the need is attended to. Should a NPC go tothe tavern to satisfy his/her Hunger, for example, the value of that need will bedecreased for as long as he/she is in the tavern (see Figure 5.2), preferably untilthe need is fully satisfied (i.e. the value reaches zero). Should another need reach”attention needed”-levels while the Hunger is attended to, however, this need will

Chapter 5. Approach 12

Figure 5.2: Thals, one of the NPCs within the module, movement with needs imple-mented.

become the most urgent and the NPC will move on to attend that one instead.A module was created that could be implemented both with (Module Need)

and without (Module Normal) the need-based system. Module Normal being anexperience very similar, albeit a lot shorter, to the regular Neverwinter Nightsstory.

5.3 Testing Dimensions

To test whether or not the use of the need-based system enhance the game ex-perience, dimensions relating to said experience were defined. Based on thesedimensions, described below, a test environment could be designed.

5.3.1 Dynamic and Life-like NPCs

One of the main reason for implementing a need-based system within a SPRPGwas to give the impression that the NPCs were alive and had needs and desires of

Chapter 5. Approach 13

their own. It was also an important feature that the NPCs feel less static duringthe course of the game experience.

This dimension was designed to gauge whether the NPCs would feel moredynamic and gives the impression of being alive, once the need-based system isimplemented.

5.3.2 Change in NPC Behavior

When having a need-based system implemented opportunity to change the be-haviour of the NPC presents itself. Just like a human being may become irritatedor testy when hungry or tired, so could a NPC change its behavior once a needor desire becomes too urgent.

This dimension was created to measure how evident the change in NPC be-havior is to the player.

5.3.3 Engaging Experience

The use of a need-based system does not, in itself, necessarily create a more en-gaging game experience and whether or not a game experience can be consideredengaging can depend on many factors. However, using the need-based systemmight very well increase the players engagement in the game and this dimensionserves to determine whether it does.

5.3.4 Elusive NPCs

Given that once the NPCs have needs and desires of their own, the quests theyprovide might be more di�cult to finish, their shops may be less available andthe information they have might become less accessible, it is not unlikely that thefeeling of having to put more e↵ort in to completing the game is increased.

This dimension serves to discover whether the players find the game harderor more challenging to complete once the need-based system is implemented.

5.4 Testing

The system was tested by allowing a number of people to play the custom modulefor Neverwinter Nights twice. Once with the system in place and once withoutand then answering questionnaires regarding their experience.

This module was used to test whether or not the implementation of a need-based system in Neverwinter Nights™ actually enhances the gameplay experienceand creates a more vivid and challenging game environment.

Both modules were then played by 24 test subjects of varying age and previousgame experience. The age of the test subjects ranged from 19 to 32, with a mean

Chapter 5. Approach 14

of 23.1 years and a Standard Deviation (SD) of 2.9 years. 23 out of the 24 testsubjects were male and all test subjects were students at Blekinge Institute ofTechnology, all of them studying game development.

After each module, each subject were given a questionnaire to fill out, con-taining questions designed to assess their experience with the current module.The questionnaire was identical for both modules, to gauge the experiences sep-arately(see appendix A.2). After having tested both modules, each test subjectwere given a third questionnaire with questions designed to di↵erentiate betweenthe two modules, along with questions regarding their age, occupation, gaminghabits and such (see appendix A.1).

To be able to analyse if playing one module would a↵ect the experience withthe other and to avoid other e↵ects, such as any bias from having already expe-rienced the modules quests and interactions, a counterbalance was used, wherehalf of the test subjects played Module Normal first and Module Need last andvice versa.

Chapter 6

Results

The results presented are based on 24 test subjects that each were given threequestionnaires during their test experience. The results show whether or not thegame experience of the Neverwinter Nights module was enhanced by the imple-mentation of the need-based system, based on four dimensions and the question-naire statements related to them (see Table 6.1).

Dimension Related Questions

Dynamic and life-like NPCsThe characters seemed activeThe characters felt like-likeThe characters seems to have their own needs

Change in NPC behaviorThe characters were in the same mood through the entire gameThe characters had the same behavior through the entire game

Engaging experienceThe game o↵ered an engaging environmentThe game seemed unusual and strange

Elusive NPCsThe characters acted in a confusing wayThe NPCs were hard to find and to follow

Table 6.1: Dimensions and their related statements

6.1 Dynamic and life-like NPCs

The dimension Dynamic and Life-like NPCs were created using the first threequestions of the questionnaires. High results in this dimension indicate higherdynamic and life-like NPCs. According to Pallant [8] a Cronbach-Alpha of 0.7or more is regarded to show internal consistency. The results of this dimensionyielded a Cronbach-Alpha of above 0.781.

Based upon the results of the first three statements in the Module Question-naire (see Appendix A.2), it was clear that Module Need gave a higher impressionof life-like and dynamic NPCs. The compounded mean of this dimension, whenplaying Module Normal, was 1.9 (SD 0.81), whereas in Module Need it was justabove 3.6 (SD 0.86), significantly higher. The di↵erence between the two moduleswere shown to be significant by using a paired samples t-test (p = 0.000)

When playing Module Normal first, both means were slightly higher. Mod-ule Normal: 2.3 (SD 0.93) and Module Need: 3.9 (SD 0.94), but the di↵erence

15

Chapter 6. Results 16

dimension Module Need Module NormalMean SD Mean SD P

Dynamic and life-like NPCs 3.6 0.86 1.9 0.81 0.000Change in NPC behavior 3.4 1.02 4.25 0.64 0.001

Table 6.2: The means, SDs and p-value of each module for every dimension, for alltwenty-four test subjects, disregarding the order in which the modules were played.

between them remain more or less the same. The same trend was present whenModule Need was played first, but instead the means were slightly lower: ModuleNormal: 1.6 (SD 0.55) and Module Need: 3.4 (SD 0.8). The di↵erence betweenthe two means were, again, almost the same.

The results also show that only two people found that Module Normal hadmore active NPCs and another two thought that it had NPCs that felt more alivethan Module Need.

6.2 Change in NPC Behaviour

Low results in this dimension indicate higher change in NPC behaviour. TheCronbach-Alpha of this dimension, based upon the two questions shown in Table6.1, is above 0.821, showing internal consistency.

The results of the statements related to this dimension show that the varyingNPC behavior was not significantly more evident in Module Need than in ModuleNormal, where the behaviour of the NPCs actually did not change.

The results of the statements related to this dimension show that there issignificant di↵erence between Module Need and Module Normal (p = 0.001).The compounded mean of this dimension in Module Normal was 4.25 (SD 0.64)and 3.4 (SD 1.02) in Module Need. The di↵erence in this dimension were shownto be significant with the use of a paired samples t-test.

When Module Need was played first, the mean of that module was significantlyhigher: 3.9 (SD 0.71), while the mean of Module Normal was only increasedslightly to 4.5 (SD 0.56). Vice versa, when Module Normal was played first,Module Normal had a mean of 4.0 (SD 0.67), while Module Need was at only 2.9(SD 1.12).

6.3 Engaging Experience

This dimension was designed to gauge whether the need-based system made wayfor a more engaging gaming experience than one without it. While the dimensiondid not show internal consistency, the questions by themselves are reported.

The results of the first question of this dimension, does show that the need-based system did result in a more engaging experience with a mean of almost 3.0

Chapter 6. Results 17

(SD 1.2) in Module Need, whereas Module Normal had a mean of 2.3 (SD 0.95),significantly lower(p = 0.003).

The second question showed similar results, with a mean of 3.3 (SD 1.36),while Module Normal had a mean of 2.4 (SD 1.35), (p = 0.009).

The di↵erences were tested using Wilcoxon signed rank test.

Questions Module Need Module NormalMean SD Mean SD P

The game o↵ered an engaging experience 3.0 1.2 2.3 0.95 0.003The game seemed unusual and strange 3.3 1.36 2.4 1.35 0.009

Table 6.3: Questions related to third dimension.

6.4 Elusive NPCs

This dimension serves to test whether or not the challenge of the game increaseswith the use of the need-based system. The dimension did not prove to haveinternal consistency, but the answers of each question on its own are reported togive relevant results.

Given that the mean of Module Need regarding whether the NPCs behavedin a confusing way was 3.04 (SD 1.33) and that the mean of Module Normal was1.8 (0.82), (p = 0.002).

Regarding whether the NPCs were hard to find and to follow, the mean ofModule Need were 3.8 (SD 0.98) and the mean of Module Normal were 2.4 (SD1.34), (p = 0.001).

The di↵erence were tested using Wilcoxon signed rank test.

Questions Module Need Module NormalMean SD Mean SD P

The characters acted in a confusing way 3.04 1.33 1.8 0.82 0.002The NPCs were hard to find and to follow 3.8 0.98 2.4 1.34 0.001

Table 6.4: Questions related to fourth dimension.

Chapter 7

Discussion & Conclusion

The method that was used provided a good structure and scope within which theneed-based system could be tested and evaluated. The simple module provideda quick, e�cient way to test the prototype without having engage test subjectsin a lengthy, potentially arduous experiment. However, the short prototype andsmall group of test subjects, while very well suited for the scope of this thesis,may not have provided enough data to draw any final conclusions.

Further, the choice of test subjects, though not intentional, may have swayedthe results to some degree. Given that all test subjects were students of gamedevelopment at Blekinge Institute of technology and that most of them are veryfamiliar with gaming, they results may have been coloured, somewhat. However,the fact that the test subject were all highly familiar with games and the develop-ment process may have made them more critical to the prototype and thus givenbetter results than subjects with little or less gaming experience.

Below are conclusions related to the two dimensions that showed internalconsistency and to the four questions that had to be separated.

7.1 Dynamic and life-like NPCs

The mean of Module Need was a lot higher than that of Module Normal, whichindicates that the need-based system did in fact create, or aided in creating, moredynamic and vivacious NPCs. The standard deviation was just about the samefor both modules (0.86 and 0.81), which suggests that even though there wassome disparity regarding how life-life and dynamic the NPCs were, it was thesame on both modules. The disparity regarding this dimension is probably aresult of some other, unknown factor, such as that di↵erent test subjects perceivethe environment di↵erently.

The di↵erence between the two means were about the same, regardless ofwhether Module Need was played first or not. However, the means were slightlyhigher when Module Normal was played first, which suggests that once a playerhas played Module Normal the vivacity of the NPC within Module Need is in-creased. Not surprisingly, when able to compare the NPCs of Module Need withthe ones that have no needs, the modules vivacity are perceived to be greater.

18

Chapter 7. Discussion & Conclusion 19

When Module Need was played first, the means were, as stated in Results,slightly lower. While this suggests that when played first, the vivacity and dy-namic of the NPCs of Module Need is not as obvious as when compared to ModuleNormal, it also shows that the vivacity and dynamic of the NPCs within ModuleNormal is perceived to be even lower once a module with the need-based system(Module Need) has been played.

7.2 Change in NPC behavior

Given that the di↵erence between the mean of Module Need and the mean ofModule Standard was roughly 0.8 units apart, the need-based system did o↵erchanges in the behavior of the NPCs. At least more so than the module without itand there was a significant di↵erence, the small di↵erence between means suggestthat the changing behaviour was not highly evident.

The large di↵erence in the standard deviations, where Module Need had thehigher one, would suggest that there was a lot more disparity regarding thechanges in behaviour in Module Need than in Module Normal. While it is quiteobvious that the disparity of Module Normal is low, since there literally were nochanges in behavior, the fact that Module Need had such a high standard devia-tion shows that even though some test subjects did find that the NPCs changedtheir behaviour, quite a few did not. This could be a result of some players finish-ing the quests faster than others, thus not getting to experience all the changesin NPC behaviour.

Furthermore, the mean of Module Need was actually increased when it wasplayed first, showing that when there was no comparison with Module Normal,the change in NPC behavior was even less obvious. Vice versa, the mean ofModule Need was lower when Module Normal was played first, which wouldsuggest that the changing behavior was especially evident when Module Needcould be compared with Module Normal (i.e. when it could be compared to amodule without any changing behavior).

7.3 The game o↵ered an engaging experience

The mean of Module Need was indeed higher than that of Module Normal, whichsuggests that, even though the di↵erence was small, it was a more engagingexperience to play Module Need than Module Normal. As with Dynamic andLife-like NPCs, the standard deviation between the two modules was very small,suggesting that, again, the disparity was caused by some other factor, rather thanthe need-based system.

The order in which the modules were played showed to make no di↵erenceregarding the mean of Module Need, whereas the mean of Module Normal was

Chapter 7. Discussion & Conclusion 20

significantly lower when played second. This suggests, quite clearly, that once amodule with the need-based system (Module Need) has been played, the engagingexperience of one without (Module Normal) is decreased. It also shows thatregardless of whether the module has been played before, it is still more engagingto play it with the need-based system implemented.

7.4 The game seemed unusual and strange

The di↵erence between the mean of Module Need and that of Module Normalwas quite significant, with Module Need having the higher. This shows that thetest subjects did indeed find Module Need to be a more strange and unusualexperience, suggesting that they were unfamiliar with the experience of a need-based system within a game experience such as this one.

While the standard deviation of Module Need was quite high (1.36) it wasvery similar to that of Module Normal (1.35), suggesting that the disparity wascaused by some other factor than the use of a need-based system. Since Never-winter Nights is quite an old game it may be that many of the test subjects wereunfamiliar with the environment in its entirety and thus found the game to beunusual and strange.

7.5 The characters acted in a confusing way

Based on the mean of the two modules, it is quite clear that the NPCs of Moduleneed acted more confusingly the ones in Module Normal. Module Need also hada lower standard deviation than Module Normal, suggesting that not only wasModule Need more challenging; the test subjects also showed less disparity intheir view of the confusing NPCs with that module.

7.6 The NPCs were hard to find and to follow

Given that the mean of Module Need were higher(and the SD lower) than that ofModule Normal, the results shows that the NPCs were harder to find and followin Module Need. In Module Normal were the NPCs actually never leave theirstarting position, it’s not surprising that the mean is this low.

Module Need, where the NPCs moved around and could, potentially ”disap-pear” while the player attended to their quest, did indeed provide a environmentwhere the NPCs were hard to find and follow. This conclusion is strengthened bythe fact that when compared to Module Normal, where the only obstacle was tofind each NPCs’ starting position, there was still less disparity regarding ModuleNeed. The test subject agreed more on the question when playing Module Needthan when playing Module Normal.

Chapter 7. Discussion & Conclusion 21

7.7 Final Conclusions

Though not all dimensions proved to show internal consistency, the questionsrelating to those dimensions still yielded telling results.

Throughout the tests, the results indicate that the implementation of a need-based system does enhance the game experience regarding the four di↵erent di-mensions stated in Table 6.1. While there certainly was a few test subjects thatdid not agree with the hypothesis, the need-based system, as implemented withinNeverwinter Nights, show a strong indication of having enhanced the game expe-rience for most players.

This implementation is a prototype and was tested within a small modulethat could be finished within approximately twenty minutes time. Even giventhose circumstances, and the fact that it was only tested on 24 subjects, it wasindicated that the implementation of a need-based system can enhance the gameexperience of an entire SPRPG, though it can not be stated to a certainty withinsuch a small scope as this theses.

As stated above, the results of the test can be considered an indication thatan implementation of a need-based system, such as this prototype, can enhancethe experience and be a welcome component within a SPRPG. Based upon thisprototype, a more rigorous and complete system could be implemented whichcan, and probably will, grant a more engaging and challenging experience.

In conclusion, this need-based system, being a prototype, did enhance the ex-perience of a short module within a well-established SPRPG (Neverwinter Nights)and it can therefore be argued that a complete and well-tested need-based systemwill serve to enhance the game experience of a SPRPG, given the right circum-stances.

Chapter 8

Future work

The next step for this system would likely be to further develop and designthe need-based system to become more versatile and modular, allowing it to beimplemented within other environments than the Aurora toolset.

An object-oriented solution in a programming language such as C++ wouldbe a good step towards making this need-based system a system usable for manygames, especially those not released yet. The scripting language of the AuroraToolset, albeit powerful, is not particularly flexible and does not give opportunityfor modular solution.

The system itself could also be enhanced further by developing more levels ofneeds, beyond primary and secondary, a system for how the needs could interactand further alter the behaviour of the NPCs.

Furthermore, the tests could be made more extensive and elaborate by in-creasing both the number of test subjects and the amount of time spent witheach module (i.e. expanding the module). Further testing could also involvetest subjects that are not students of game development, thus potentially givingresults more closely related to that of regular players.

Further ahead in time would be the development and design of a C++ RPGlibrary containing, among other features, a highly enhanced version of this need-based system.

22

References

[1] Ernest Adams. Fundamentals of game design. New Riders, 2010.

[2] Christine Bailey and Michael Katchabaw. An emergent framework for realis-tic psychosocial behaviour in non player characters. Proceedings of the 2008

Conference on Future Play Research, Play, Share - Future Play ’08, page 17,2008.

[3] Leif Gruenwoldt and Michael Katchabaw. Creating Reactive Non PlayerCharacter Artificial Intelligence In Modern Video Games. 2005.

[4] Abraham H Maslow. A theory of human motivation. Published in Psycho-

logical Review 50, 1943.

[5] John Mccarthy. Programs with common sense. pages 1–15, 1959.

[6] N/A. Maslows Hierarchy of Needs picture. https://en.wikipedia.org/

wiki/File:Maslow\%27s_Hierarchy_of_Needs.svg, 2013. [Online; ac-cessed 29-June-2013].

[7] N/A. Pacman by Namco. http://en.wikipedia.org/wiki/Pacman, 2013.[Online; accessed 27-May-2013].

[8] Julie Pallant. SPSS survival manual: A step by step guide to data analysis

using SPSS. Open University Press, 2010.

[9] Steve Rabin. AI game programming wisdom. Cengage Learning, 2002.

[10] Steve Rabin. Introduction to game development, volume 2. Charles RiverMedia, 2010.

[11] Bob Scott. The Illusion of Intelligence. In Steve Rabin, editor, AI game

programming wisdom, pages 16–21. Cengage Learning, 2002.

[12] Penelope Sweetser and Peta Wyeth. GameFlow : A Model for EvaluatingPlayer Enjoyment in Games. 3(3):1–24, 2005.

[13] Paul Tozour. The Evolution of Game AI. In Steve Rabin, editor, AI game

programming wisdom, pages 3–16. Cengage Learning, 2002.

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Appendix A

Appendix

Construct Module Need Module NormalMean SD Mean SD

Dynamic and life-like NPCs 3.9 0.94 2.259 0.93Change in NPC behavior 2.9 1.1 4.0 0.67Engaging experience 3.1 1.02 2.7 0.92Elusive NPCs 3.1 0.68 2.6 0.87

Table A.1: The means and SDs of each module for every construct, for the twelvetest subjects that played Module Normal first.

Construct Module Need Module NormalMean SD Mean SD

Dynamic and life-like NPCs 3.4 0.8 1.6 0.55Change in NPC behavior 3.8 0.71 4.5 0.56Engaging experience 3.2 0.86 1.9 0.96Elusive NPCs 3.7 0.78 1.6 0.58

Table A.2: The means and SDs of each module for every construct, for the twelvetest subjects that played Module Need first.

QuestionsWhich module did you find to be the most challenging?Which module did you find to be more fun?Which module did you find to be more life-like?How many hours a week do you spend on digital games?How many hours a week do you spend on digital RPG games?What gender are you?What’s your age?What is your(main) occupation?What could be done to improve the need-based system

Table A.3: Questions from A.1 translated to English

24

Appendix A. Appendix 25

Edit this form

PostPlay QuestionnaireDetta formulär ska fyllas i efter att ha spelat igenom både ModuleNoNeed(A) och ModuleNeed(B)* Required

Testnummer *Fråga Gunnar om du undrar

Vilken modul fann du vara mest utmanande? *

ModuleNoNeed(A)

ModuleNeed(B)

Vet ej

Vilken modul fann du vara roligast? *

ModuleNoNeed(A)

ModuleNeed(B)

Vet ej

Vilken modul fann du vara mest levande? *

ModuleNoNeed(A)

ModuleNeed(B)

Vet ej

Hur många timmar i veckan spenderar du till digitala spel? *

Hur många timmar i veckan spenderar du till digitala RPG-spel? *

Kön? *

Man

Kvinna

Ålder? (Ex: 24, 33, 102) *Endast siffror, ingen text

Vad är din (huvudsakliga)sysselsättning? *Student, Arbete? Specificera gärna

PostPlay Questionnaire https://docs.google.com/forms/d/1POt-q3ZyMRKYg9AecR-...

1 of 2 5/26/13 7:14 PM

Figure A.1: The Postplay Questionnaire filled out after having played both modules.

Appendix A. Appendix 26

Edit this formModule Questionnaire

* Required

Testnummer *Fråga Gunnar om du undrar

Spelets karaktärer kändes aktiva *

1 2 3 4 5

Håller inte med alls Håller med fullständigt

Spelets karaktärer kändes levande *

1 2 3 4 5

Håller inte med alls Håller med fullständigt

Spelets karaktärer verkade ha egna behov *

1 2 3 4 5

Håller inte med alls Håller med fullständigt

Spelets karaktärer hade samma typ av beteende genom hela spelet *

1 2 3 4 5

Håller inte med alls Håller med fullständigt

Karaktärerna i spelet verkade alltid vara på samma humör *

1 2 3 4 5

Håller inte med alls Håller med fullständigt

Spelet erbjöd en engagerande upplevelse *

1 2 3 4 5

Håller inte med alls Håller med fullständigt

Spelet kändes ovanligt, främmande *

1 2 3 4 5

Håller inte med alls Håller med fullständigt

Module Questionnaire https://docs.google.com/forms/d/17XsLU_wdI38rj1g3A__G...

1 of 2 5/26/13 7:11 PM

Figure A.2: The Module Questionnaire to be filled out after having played eachmodule.

Appendix A. Appendix 27

QuestionsThe characters seemed activeThe characters felt like-likeThe characters seems to have their own needsThe characters were in the same mood through the entire gameThe characters had the same behavior through the entire gameThe game o↵ered an engaging environmentThe game seemed unusual and strangeThe characters acted in a confusing wayThe NPCs were hard to find and to follow

Table A.4: Questions from A.2 translated to English