William Costello
@williamcostello.bsky.social
PhD student of Evolutionary Psychology at the University of Texas at Austin.
Pinned
Out now and open access for four weeks as the editor's choice Topic in Focus in American Psychologist.
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
In our new American Psychologist paper, we debunk the decades old zombie idea that evolutionary psychology is unfalsifiable.
🧵
🧵
Reposted by William Costello
People don't like individuals who vigilantly monitor and reprimand wrongdoings at work.
These "hall monitors" are seen as less moral and hyper competitive (the only people who like them are other vigilantes).
www.sciencedirect.com/science/arti...
These "hall monitors" are seen as less moral and hyper competitive (the only people who like them are other vigilantes).
www.sciencedirect.com/science/arti...
February 5, 2026 at 7:24 PM
People don't like individuals who vigilantly monitor and reprimand wrongdoings at work.
These "hall monitors" are seen as less moral and hyper competitive (the only people who like them are other vigilantes).
www.sciencedirect.com/science/arti...
These "hall monitors" are seen as less moral and hyper competitive (the only people who like them are other vigilantes).
www.sciencedirect.com/science/arti...
Reposted by William Costello
The belief that evolutionary psychology makes unfalsifiable hypotheses is old, but deeply misconceived:
New paper by @costellowilliam @ProfDavidBuss et al.
psycnet.apa.org/fulltext/202...
New paper by @costellowilliam @ProfDavidBuss et al.
psycnet.apa.org/fulltext/202...
February 5, 2026 at 12:50 PM
The belief that evolutionary psychology makes unfalsifiable hypotheses is old, but deeply misconceived:
New paper by @costellowilliam @ProfDavidBuss et al.
psycnet.apa.org/fulltext/202...
New paper by @costellowilliam @ProfDavidBuss et al.
psycnet.apa.org/fulltext/202...
Reposted by William Costello
Risk of contracting sexually transmitted infections may be elevated for women during the days when the endometrium is receptive to embryo implantation (“the implantation window”).
Decreased Sexual Motivation during the Human Implantation Window - HBES
– by James R. Roney A lot of research has investigated shifts in women’s psychology and behavior across different phases of the menstrual cycle. One pattern that has emerged in multiple studies is an…
www.hbes.com
February 4, 2026 at 4:01 PM
Risk of contracting sexually transmitted infections may be elevated for women during the days when the endometrium is receptive to embryo implantation (“the implantation window”).
Reposted by William Costello
Now out in Evolutionary Psychological Science.
OA link: rdcu.be/e2g4X
OA link: rdcu.be/e2g4X
February 4, 2026 at 10:24 AM
Now out in Evolutionary Psychological Science.
OA link: rdcu.be/e2g4X
OA link: rdcu.be/e2g4X
Reposted by William Costello
This week, we talk to @joshtybur.bsky.social about the immune system in your head. 🤯
youtu.be/O0t8WpICTyo
www.podbean.com/eas/pb-x6vk5...
podcasts.apple.com/us/podcast/e...
youtu.be/O0t8WpICTyo
www.podbean.com/eas/pb-x6vk5...
podcasts.apple.com/us/podcast/e...
The Behavioral Immune System with Josh Tybur
YouTube video by Evolutionary Psychology (The Podcast)
youtu.be
February 3, 2026 at 4:48 PM
This week, we talk to @joshtybur.bsky.social about the immune system in your head. 🤯
youtu.be/O0t8WpICTyo
www.podbean.com/eas/pb-x6vk5...
podcasts.apple.com/us/podcast/e...
youtu.be/O0t8WpICTyo
www.podbean.com/eas/pb-x6vk5...
podcasts.apple.com/us/podcast/e...
Thanks for taking the time to review our paper and other recent work from our lab.
We will try to take your constructive criticism on board going forward.
I will respond to a few points here in this thread.
We will try to take your constructive criticism on board going forward.
I will respond to a few points here in this thread.
I reviewed an earlier version of this paper. I think it's interesting, because you can tell by reading it that evolutionary psychology still lacks a loyal opposition and a healthy error culture.
It's a defensive paper, targeted at people who believe evolution stops at the neck, YouTubers, _others_
It's a defensive paper, targeted at people who believe evolution stops at the neck, YouTubers, _others_
Out now and open access for four weeks as the editor's choice Topic in Focus in American Psychologist.
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
February 3, 2026 at 5:56 PM
Thanks for taking the time to review our paper and other recent work from our lab.
We will try to take your constructive criticism on board going forward.
I will respond to a few points here in this thread.
We will try to take your constructive criticism on board going forward.
I will respond to a few points here in this thread.
Reposted by William Costello
People strongly prefer to date someone who shares their politics (r=.62). Only 7.7% of couples are dating someone from the opposite political party (a Democrat dating a Republican).
People who see their partners as politically dissimilar have worse relationships
sites.lsa.umich.edu/whirl/wp-con...
People who see their partners as politically dissimilar have worse relationships
sites.lsa.umich.edu/whirl/wp-con...
February 1, 2026 at 11:08 PM
People strongly prefer to date someone who shares their politics (r=.62). Only 7.7% of couples are dating someone from the opposite political party (a Democrat dating a Republican).
People who see their partners as politically dissimilar have worse relationships
sites.lsa.umich.edu/whirl/wp-con...
People who see their partners as politically dissimilar have worse relationships
sites.lsa.umich.edu/whirl/wp-con...
Reposted by William Costello
Bonus: Response to two comments: buff.ly/WyjrbJo
TL;DR:🧵 by @williamcostello.bsky.social: buff.ly/LTMlCRR
2/2
TL;DR:🧵 by @williamcostello.bsky.social: buff.ly/LTMlCRR
2/2
February 1, 2026 at 4:09 PM
Bonus: Response to two comments: buff.ly/WyjrbJo
TL;DR:🧵 by @williamcostello.bsky.social: buff.ly/LTMlCRR
2/2
TL;DR:🧵 by @williamcostello.bsky.social: buff.ly/LTMlCRR
2/2
Reposted by William Costello
Unlike the general *biological* Theory of Evolution, evolutionary psychology doesn’t even have fossils to counter criticism of unfalsifiability.
But @williamcostello.bsky.social et al put up a robust defence of the falsifiability and testability of its hypotheses:
buff.ly/I9fS5nf
1/2
But @williamcostello.bsky.social et al put up a robust defence of the falsifiability and testability of its hypotheses:
buff.ly/I9fS5nf
1/2
February 1, 2026 at 4:09 PM
Unlike the general *biological* Theory of Evolution, evolutionary psychology doesn’t even have fossils to counter criticism of unfalsifiability.
But @williamcostello.bsky.social et al put up a robust defence of the falsifiability and testability of its hypotheses:
buff.ly/I9fS5nf
1/2
But @williamcostello.bsky.social et al put up a robust defence of the falsifiability and testability of its hypotheses:
buff.ly/I9fS5nf
1/2
Reposted by William Costello
⚡️"an often-overlooked aspect of evolutionary psychology: It holds itself to a higher standard than many other human behavioral sciences regarding evidentiary burden"
psycnet.apa.org/fulltext/202...
psycnet.apa.org/fulltext/202...
January 30, 2026 at 7:48 PM
⚡️"an often-overlooked aspect of evolutionary psychology: It holds itself to a higher standard than many other human behavioral sciences regarding evidentiary burden"
psycnet.apa.org/fulltext/202...
psycnet.apa.org/fulltext/202...
Reposted by William Costello
The evolutionary psychological hypothesis that ‘humans faced adaptive problem X, and so have adaptive solution Y’, can be falsified by showing that ‘they did not face problem X’, and/or ‘they do not have solution Y’ 🤷♂️
In our new American Psychologist paper, we debunk the decades old zombie idea that evolutionary psychology is unfalsifiable.
🧵
🧵
Out now and open access for four weeks as the editor's choice Topic in Focus in American Psychologist.
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
January 30, 2026 at 1:47 PM
The evolutionary psychological hypothesis that ‘humans faced adaptive problem X, and so have adaptive solution Y’, can be falsified by showing that ‘they did not face problem X’, and/or ‘they do not have solution Y’ 🤷♂️
Reposted by William Costello
"study supports a putative universality of attractiveness halo effects and also contributes to a deeper understanding of subtle variations in the halo effects of men’s and women’s attractiveness in more individualistic versus more collectivistic cultures"
A Cross-Cultural Comparison of the Attractiveness Halo Effect in Men and Women: https://osf.io/v9a67
January 29, 2026 at 9:41 PM
"study supports a putative universality of attractiveness halo effects and also contributes to a deeper understanding of subtle variations in the halo effects of men’s and women’s attractiveness in more individualistic versus more collectivistic cultures"
In our new American Psychologist paper, we debunk the decades old zombie idea that evolutionary psychology is unfalsifiable.
🧵
🧵
Out now and open access for four weeks as the editor's choice Topic in Focus in American Psychologist.
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
January 30, 2026 at 10:23 AM
In our new American Psychologist paper, we debunk the decades old zombie idea that evolutionary psychology is unfalsifiable.
🧵
🧵
Reposted by William Costello
🎯"Their discussion is relevant to all of psychology given the well-documented issues with empirical replications and ideological bias within academia more broadly" psycnet.apa.org/fulltext/202...
January 30, 2026 at 1:35 AM
🎯"Their discussion is relevant to all of psychology given the well-documented issues with empirical replications and ideological bias within academia more broadly" psycnet.apa.org/fulltext/202...
Reposted by William Costello
"False facts are highly injurious to the progress of science, for they often endure long...several evolutionary psychological hypotheses have generated specific, falsifiable predictions; undergone multiple empirical tests; and been refuted" psycnet.apa.org/fulltext/202...
January 29, 2026 at 7:02 PM
"False facts are highly injurious to the progress of science, for they often endure long...several evolutionary psychological hypotheses have generated specific, falsifiable predictions; undergone multiple empirical tests; and been refuted" psycnet.apa.org/fulltext/202...
Out now and open access for four weeks as the editor's choice Topic in Focus in American Psychologist.
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
January 29, 2026 at 5:08 PM
Out now and open access for four weeks as the editor's choice Topic in Focus in American Psychologist.
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
Contrary to popular belief, evolutionary psychology hypotheses are testable and falsifiable.
psycnet.apa.org/fulltext/202...
New in Evolution and Human Behavior from Buss lab members past and present.
Project started in my 1st year of grad school & led by Rebecka Hahnel-Peeters.
Men underestimate how upset women feel after sexual assault.
Women overestimate how upset men feel.
www.sciencedirect.com/science/arti...
Project started in my 1st year of grad school & led by Rebecka Hahnel-Peeters.
Men underestimate how upset women feel after sexual assault.
Women overestimate how upset men feel.
www.sciencedirect.com/science/arti...
January 29, 2026 at 2:28 PM
New in Evolution and Human Behavior from Buss lab members past and present.
Project started in my 1st year of grad school & led by Rebecka Hahnel-Peeters.
Men underestimate how upset women feel after sexual assault.
Women overestimate how upset men feel.
www.sciencedirect.com/science/arti...
Project started in my 1st year of grad school & led by Rebecka Hahnel-Peeters.
Men underestimate how upset women feel after sexual assault.
Women overestimate how upset men feel.
www.sciencedirect.com/science/arti...
Reposted by William Costello
Important: evolutionary mismatch is not a vague just-so story. It generates testable predictions about when traits should become impairing: rapid environmental change, decoupling of cues from outcomes, and loss of developmental calibration.
January 19, 2026 at 1:18 AM
Important: evolutionary mismatch is not a vague just-so story. It generates testable predictions about when traits should become impairing: rapid environmental change, decoupling of cues from outcomes, and loss of developmental calibration.
Reposted by William Costello
"[M]ale’s sexual overperception bias strengthens throughout mid-to-late adolescence and may first emerge around age 17. In contrast, female’s sexual underperception bias appears to be activated and relatively stable already by age 16."
I thought we were just friends! Emergence of Sexual Misperception Biases in Adolescence - HBES
– by Marius Stavang Imagine you’re on a movie date with someone. Everything seems to be going great. The conversation flows easily, you laugh together, you exchange smiles—there’s chemistry. After the...
www.hbes.com
January 15, 2026 at 8:48 PM
"[M]ale’s sexual overperception bias strengthens throughout mid-to-late adolescence and may first emerge around age 17. In contrast, female’s sexual underperception bias appears to be activated and relatively stable already by age 16."
Thrilled that our forthcoming article in American Psychologist: “Evolutionary Psychology Hypotheses Are Testable and Falsifiable” has been chosen as the journal’s Topic in Focus & Editor’s Choice.
Coming soon with two commentaries + our reply.
Open access for the first 4 weeks.
Coming soon with two commentaries + our reply.
Open access for the first 4 weeks.
January 16, 2026 at 8:04 PM
Thrilled that our forthcoming article in American Psychologist: “Evolutionary Psychology Hypotheses Are Testable and Falsifiable” has been chosen as the journal’s Topic in Focus & Editor’s Choice.
Coming soon with two commentaries + our reply.
Open access for the first 4 weeks.
Coming soon with two commentaries + our reply.
Open access for the first 4 weeks.
Terrific essay from Mitch Brown, one of the best ambassadors our field could hope for.
inquisitivemag.org/articles/fie...
inquisitivemag.org/articles/fie...
December 15, 2025 at 10:53 PM
Terrific essay from Mitch Brown, one of the best ambassadors our field could hope for.
inquisitivemag.org/articles/fie...
inquisitivemag.org/articles/fie...
Reposted by William Costello
👍"As anyone in my field will tell you, humans evolved to maintain bonds through cooperation and helping each other. So I view my conversations with skeptics and critics in this light and as a perfect way to highlight this fact."
A Field Guide to Evolutionary Psychology — Inquisitive
Part of the job of an evolutionary psychologist is to educate people who are skeptical, or even critical, of what we do
inquisitivemag.org
December 15, 2025 at 10:00 PM
👍"As anyone in my field will tell you, humans evolved to maintain bonds through cooperation and helping each other. So I view my conversations with skeptics and critics in this light and as a perfect way to highlight this fact."
Reposted by William Costello
One of the clearest predictors of trust in groups is visibility—knowing who contributes, who helps, and who withdraws. Hunter-gatherer cooperation relied on transparency. Digital life reverses this: everyone sees the outcomes, almost no one sees the processes.
December 14, 2025 at 11:30 AM
One of the clearest predictors of trust in groups is visibility—knowing who contributes, who helps, and who withdraws. Hunter-gatherer cooperation relied on transparency. Digital life reverses this: everyone sees the outcomes, almost no one sees the processes.
Reposted by William Costello
The safest place on the internet is the r/bald subreddit. I have no idea why this came up on my Reddit, but I now follow religiously, as men support one another through the decision to go bald. It is SO positive and wholesome. Amazing to see men supporting each other about body-related concerns.
December 9, 2025 at 11:17 PM
The safest place on the internet is the r/bald subreddit. I have no idea why this came up on my Reddit, but I now follow religiously, as men support one another through the decision to go bald. It is SO positive and wholesome. Amazing to see men supporting each other about body-related concerns.
Reposted by William Costello
What evolutionary psychology to the rescue of the humanities looks like:
"The Cognitive Foundations of Fictional Stories"
"The Cognitive Foundations of Fictional Stories"
OSF
osf.io
December 8, 2025 at 2:23 PM
What evolutionary psychology to the rescue of the humanities looks like:
"The Cognitive Foundations of Fictional Stories"
"The Cognitive Foundations of Fictional Stories"