by Wendelin Reich and Werner Schirmer

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This is the fourth post in our series on artificial behavior and modern game AI. Find the whole series via our homepage.

Introduction

Video games have been around for more than 60 years, and it's hard to deny that they've become a mature artform. Some have amazing graphics, some can boast awesome game design, story or sound. A majority of today's high-impact games (whether defined in terms of revenue, award nominations or some other criterion) also feature non-player character (NPCs). Can we say confidently that the NPCs in these games are 'great' in the same sense as their art or design are often undeniably great? The answer depends on whether we're talking about antagonistic or collaborative NPCs.

Take three recent examples from very different genres. In the cute world of Animal Crossing: New Horizons, NPCs interact with the player in simplistic, highly scripted ways. The looped idle animations (see below) make it obvious that this simplicity is intentional. Believably interactive NPCs are just not part of the game's value proposition. (See post #2 for more on believability.)

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Two NPCs and one player in Animal Crossing: New Horizons (2020)

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Haldor the trader showing a looped animation in Valheim (2021)

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An unresponsive NPC in Cyberpunk 2077 (2020)

For our second example, Valheim only seems to feature a single collaborative NPC, at least at the time of writing: Haldor the trader. Like in Animal Crossing, Haldor displays little more than basic looped animations, and so it's clear that the developers didn't prioritize making interactions with him believable. But unlike in our first example, there is a noticeable dissonance between the believable (if stylized) graphics and the mechanistic behaviors of the NPC.

As a final example, the dissonance in Cyberpunk 2077 is even larger because the realistic graphics and the open-world nature of the game create high expectations for believable interactions with the game's many collaborative NPCs. These are then thwarted in the most basic ways (lack of eye contact, basic responsiveness etc), which even lead to a significant backlash from players when the game was released.

Of course, you could say that Animal Crossing does just fine without believable NPCs, Valheim is an edge case and Cyberpunk 2077 a disappointment. But the problem remains. The seemingly intentional choice of "wholesome" games such as Animal Crossing to use cute and simplistic NPC behaviors shouldn't distract us. It's not as if Nintendo - or anyone else - has figured out how to create believable collaborative NPCs, and then chosen not to implement them.

This is in stark contrast to all other base technologies used by today's video games, notably graphics and sound. In fact, nobody today quite knows how to create believable collaborative NPCs. The goal of this post is to convince you that this is a problem. There are four reasons why collaborative NPCs need to become significantly better.

Reason 1: Players want better, friendlier NPCs

There is already a wealth of evidence showing that players want to have better, deeper and more empathic interactions with NPCs today (see post #3 for details & sources).

Reason 2: Bad NPCs are a creative bottleneck