A list of biases applied to teams/startups/feedback…

Félix López
4 min readJul 26, 2020

This post started as a twitter thread, many people replied to it asking me to publish it as a post, so here we are.

Most of them apply to many concepts so I will try to make an example of each one but not for every concept.

Confirmation bias

Feedback: we tend to search/believe information that confirms our ideas or opinions. So, we normally believe feedback, gossip, third party feedback when it confirms what we think about someone.
Hiring: We ask questions to the candidate trying to confirm our assumptions.
Conflicts: Once we have labeled someone we’re going to see evidences of that all the time


We disregard third party feedback when is about someone in our group.


We reject negative feedback about someone when we have invested a lot on that person because that damages our self-esteem.

Attribution error

Too many times we overemphasize personal characteristics in judging others’ behavior when many times the problem is the situation. E.g We set up someone to fail but we blame them.
Conflicts When there is a problem with someone we tend to attribute bad behavior to personal characteristics but when we are the ones causing the problem we attribute it to the situation. E.g She didn’t manage to meet the deadline because she’s lazy. I didn’t manage to meet the deadline because I have too many things on my table.

Affinity bias

Feedback: We downplay a problem, e.g third party feedback, just because the person is similar to us, we like them, etc. E.g we value some behaviors as normal because we would do the same way.
Hiring: We like a candidate just because we have something in common with them. We come from the same town, a previous company, know the same people, is similar to us, etc

Recency bias

Feedback: We remember better recent events over historic ones. So our feedback is based only on the last event but it’s pretty likely that person has done the same thing very well or bad in the past.

Halo effect

Feedback: Someone is so good as something that we make a general opinion on a person based just on that. This prevents the person to grow in other areas.
Hiring: we focus too heavily on one positive aspect of a candidate.

Horn effect

Feedback: This the opposite of the Halo effect. We use a negative trait to make a general opinion about someone.
Hiring something bad about the candidate negatively prevents us to value any other thing.

Conformity bias

Hiring/Decision making: Imagine that you are in a panel and you are the only one with a different idea, you are likely going to conform due to peer pressure.

Hanlon’s razor

Conflicts: Never attribute to malice that which is adequately explained by stupidity. that email that never arrives and you start to think s/he doesn’t want to answer…

Optimism bias

It can cause us to overestimate our own success in comparison to others. It goes without saying that I’ve seen this in some CEOs
project management: this bias leads to consistently overestimate the success and under-estimation of a project. Should I mention developer estimation?

Planning fallacy

Related to the previous one. It’s the human tendency to underestimate the amount of time a project will take to complete. It doesn’t matter how many times we’ve done something we’re always optimistic about the time to do that task next time.

Illusion of control

Feedback: feedback which emphasizes success rather than failure will naturally cause us to feel more in control (although we might not be the ones to take credit for it)
Project Management: involved in a project are more optimistic about its outcomes compared to those less involved. People involved in a project are more optimistic about their outcomes compared to those less involved, so listen to everyone.

IKEA effect

This is one goes directly to our heart as developers → it’s our bias towards something we’ve built ourselves. Do I need to say anything else? :D

Sunk cost fallacy

We continue a behavior or endeavor as a result of previously invested resources.
Projects/startups/teams/… Imagine a project, a startup, a pet project… Is not working or even research tells you is not going to work but we continue because we have invested too much

Anchoring effect

We rely too heavily on the first piece of information we receive.
Project management:
So when we are estimating something the first estimation will influence the rest.
Feedback: Third-party feedback can influence our judgment of someone.

Authority bias

The tendency to attribute greater accuracy to the opinion of an authority figure and be more influenced by that opinion.
Decision making: We take into consideration first the opinion from a senior just because it’s senior.
Feedback: we believe third party feedback just because it comes from someone with power.

Status-quo bias

A preference for the current state of affairs. The current baseline is taken as a reference point, and any change from that baseline is perceived as a loss.
We reject change company-wise, project-wise… The most typical example of this is: this is how’s always been done here.



Félix López

Opinions entirely my own. Engineering @tinybird ex @google . Management, critical thinking & psychology. http://medium.com/@flopezluis/