Common-knowledge effect: A bias in team decision making

did not see any of the large companies include such a simple and obviously useful app. my guess is it's too much responsibility and lawyers are against it

Depends on situation and conditions. In this UX case, assuming that information is ready, a team of 10 UX experts with similar expertise and have been working together for some time will reach the good decision.

A team consist of CEOs, managers, devs, UX, marketing/sales & finance won't get the same level of decision assuming the information is ready. However they'll be useful for information / idea gathering / brainstorming when the information is not ready, for a single person / team to make decision.

My past experience sums up to this:

* Team of similar expertise & knowledge: good & fast on decision making, lack on seeking knowledge in other part of expertise

* Team with variety of expertise & knowledge: will make slow & bad decisions more than good or fast one, in exchange of decent chance of knowledge sharing for each expertise

Of course the quality of each member, how can they work as a team, whether they have hidden personal agenda / hating each other plays part in the quality and speed of decision making too

I'd say teams are way more likely to avoid clearly bad decisions.

Now your statement is so clearly absolutist in its tone, so to speak specifically, I would say teams will largely point to the best outcome eventually but often pays the bill in over lost efficiency.

Individuals make bad takes, sometimes they have personality issues, sometimes then have a terrible day and are dialing it in at work who knows. What I know is that it's less likely that an entire team are living their worst day at the same time which could lead to catastrophically bad decisions.

Yes and the section "Team Decision Making" is really unclear about how exactly "Afterward, team members got together and were given 10 minutes to share, discuss, and determine the best project" happened:

- were each participant's rank, credentials, job title, age, experience visible ("7% Execs, 4% Prod/PM, 4% Marketing, 44% Designers , 23% UX Researchers, etc.")? Were the participants or their ranks known to each other beforehand?

- was it a roundtable? huddle? debate? unstructured free-for-all? egalitarian? squabble? shouting-match? Did they take a show-of-hands (or voice-vote) at the start and/or end to find out who chose which option?

- how exactly did the discussion dynamic go, which people or considerations dominated it, how did people decide who to let speak or listen to? Did people defer to the perceived expert/ highest ranking person/ perceived spokesperson for the majority opinion/ loudest person, or not? There can be multiple cultural and nonverbal factors. Were the Designers (or UX Researchers) more influenced by their peers than other people? Did participants make statements like "in my X years experience as Y, criterion Z is important"?

- I think the researchers (Nielsen Norman) should have run multiple controls where the same group of people get the same statements, but then vary both the "discussion" format and participants (e.g. different subsets of 7 from 9) to see how much that influences the outcome. And then do it on Slack and/or Zoom (both text-only, voice-conf and video-conf) and measure the influence of that too. Or even old-school (asynchronous email): limit the "discussion" to each participant can write one group email to everyone else, then they have 10min to individually consider their decision. And also measure whether it's influenced by whether they're anonymous, or sign their full name, or include job title.

Of course there's overlap. The idea is that they are avoiding the overlap, even though it would be a good feature.