The Mere Completion Effect: Why Players Choose to Finish

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Let's say you were grinding out some faction rep in an open world game. You're doing a series of quests with multiple steps that yield "faction points" with a group called, I dunno, "Sons of Buttered Toast." Each step in the quest chain rewards you with a specific number of faction points and you can bounce between the two quest chains. Of course, completing the last step in a questline closes it out.

Say you go to the quest vendor for the SoBT and they present this list of your current options:

Questline A step 3 of 6: Procure salted butter. Reward: 100 faction points

Questilne B step 3 of 6: Polish the butter knife. Reward: 130 faction points

Assume both tasks are equally difficult and would take the same amount of time. Which do you think you would choose next? Probably the second one, which gets you a bigger reward, right? Right.

Now imagine that the options were like this:

Questline A step 6 of 6: Procure salted butter. Reward: 100 faction points

Questline B step 3 of 6: Polish the butter knife. Reward: 130 faction points

The only difference is that the step in Questline A is now the final step in the chain. I bolded that bit for emphasis here. You don't get any bonus for completing a whole questline, just the 100 points advertised for the last step. NOW which questline would you pursue next? 

If you're like the subjects in a paper I read by Converse, Tsang, and Hennecke (2023), there's now an increased chance that you would go for Questline A even though it offers a smaller reward. It has to do with what the authors call "the mere completion effect" and it offers a powerful way that game designers subtly shape player behavior.

In their study, the authors had subjects complete simple CAPTCHA tasks, but at the beginning of each round subjects got to choose which of two tasks they would complete next. They were also shown how much money they would earn for completing it. Finally, each task was presented as a "segment" in a larger whole, with green denoting a segment that had already been completed:

Taken from Converse, Tsang, and Hennecke (2023).

In cases like the one above, most people chose the task on the left, since it paid more. Only 8.9% of subjects picked the right-hand option.

But then the experimenters presented choices that looked like this:

Again, green = already completed. When shown this, the number of subjects who picked the lower paying option on the right went from 8.9% all the way up to 23.6%! Most people still took the higher paying option, but relative to the other condition a lot more seemed willing to get less of a reward for filling in the last segment of that pie.

In another study from the same paper, the authors found a similar result when instead of choosing between tasks that paid different amounts, subjects chose between tasks that were "fun" (clicking on pictures of cute animals) or tasks that were "tedious" (typing strings of random letters backwards). When their choice included completing the last segment of a series of tasks, there was an increase in the number of people who would tolerate the tedious task.

The authors of this study dubbed this phenomenon "the mere completion effect" which they say describes how people feel inherent satisfaction (and more to the point, they perceive value) in completing the last of a set of tasks. This satisfaction can outweigh lower rewards or higher effort. 

Clever game designers could use this insight to present options to players in ways that nudge them in a desired direction, such as in the faction rep quest example above. Or they could steer players towards completing a main story quest by flagging when the current segment is the last. Or to build out an upgrade tree that unlocks new content by showing a graphical representation of all but one node filled in.

A different paper by Roberts, Imas, and Fishbach (2023) looked at this phenomenon from a slightly different angle. The authors of this paper explore how the desire to achieve goal closure often leads to seemingly irrational decisions like choosing to incur higher costs sooner rather than waiting for lower costs later. They had subjects doing a password transcription task (e.g., entering "3atAmynZ5P" into a password field) choose to either enter 17 such passwords a month from now or 20 such passwords tomorrow. In either case, they got paid for their participation in a month. A majority, 65%, of people chose to do the longer task sooner rather than wait until later for the easier task.

The authors say that the good vibes people get from completing a goal and letting go of an unfinished task make it worth the extra expense or effort needed to make it happen sooner rather than later. Even if waiting until later would require less work.

I experienced something similar when playing the factory management game, Satisfactory. It's a game of automation where reaching milestones requires crafting items. The "Field Research" milestone, for example, requires 300 spools of wire, 300 boxes of screws, and a stack of 100 iron plates.

You can reach this milestone by crafting the items by hand at a crafting bench --a dull and monotonous task that involves sitting passively while numbers creep up-- or you can build factories that automate item crafting while you go around doing other, more entertaining stuff. But crafting by hand, though dull, is also quicker than letting the machines do it. 

And so I often found myself tanking my fun by hand crafting the 100 iron plates needed to reach a milestone even though my machines were slowly doing it for me. Not because it was fun and not because I was itching to make use of the milestone reward, but because I wanted to complete the series of tasks as soon as possible and I'd do extra work to do it. The cost --in fun, in effort-- was worth it when it meant completing a series of tasks, but not before then.

REFERENCES

Converse, B. A., Tsang, S., & Hennecke, M. (2023). The Value of Mere Completion. Journal of Experimental Psychology: General, 152(11), 3021-3036. https://doi.org/10.1037/xge0001434

Roberts, A. R., Imas, A., Fishbach, A. (2023). Can't Wait to Pay: The Desire for Goal Cloasure Increases Impatience for Costs. Journal of Personality and Social Psychology, 126(6), 1019-1035. https://doi.org/10.1037/pspa0000367