Identical twins aren't 100% genetically identical. They differ by an average of 5.2 early developmental mutations. nature.com/articles/s4158…
Interesting paper! A few thoughts... [1/3]
1. It was always a safe bet that identical twins would be slightly different genetically. Indeed, there was already evidence for it (e.g., nature.com/articles/ejhg2…; HT @Scientific_Bird). The main contribution of the paper is carefully quantifying the differences. [2/3]
2. The fact that identical twins aren't genetically identical doesn't undermine twin studies. It may mean they slightly underestimate heritability. But the differences are so minor (M = 5.2 mutations in 3 billion base pairs) that, most of the time, it may have ~0 effect. [3/3]
• • •
Missing some Tweet in this thread? You can try to
force a refresh
One of the great myths of psychology: Depression is caused by a chemical imbalance in the brain. Excerpt from "Fifty Psychological and Psychiatric Terms to Avoid" by Scott Lilienfeld et al. journal.frontiersin.org/article/10.338…#RIPScottLilienfeld
TBC, this isn't to say depression isn't in the brain. All psychological phenomena are in the brain. But the evidence for the chemical imbalance model of depression, specifically, is slim at best and arguably non-existent.
Biologists define sex in terms of gamete size: Individuals that produce the smaller gametes (e.g., sperm) are male; those that produce the larger gametes (e.g., eggs) are female. But why did gamete-size dimorphism evolve in the first place? Nice overview: aeon.co/essays/the-exi…
"[C]hromosomes aren't called 'male' or 'female' because these bits of DNA define biological sex. It's the other way around – in some species that reproduce using two discrete sexes, those sexes are associated with different bits of DNA." aeon.co/essays/the-exi…
"The physical characteristics of an organism can be labelled as 'male' or 'female' only if there is already a definition of sex... This explains why the existence of individuals with combinations of male and female characteristics doesn't show that biological sex is a continuum."
Slow-motion woodpecker. Woodpeckers have various adaptations that allow them to avoid injury despite bashing their faces into trees thousands of times a day. These include thick, spongy skulls that protect their brains and specialized, protective eyelids. imgur.com/gallery/RDAU5p3
Time-lapse footage of a woodpecker making a nest cavity in a tree 🔊
New paper! Reactions to Male-Favouring versus Female-Favouring Sex Differences: A Pre-Registered Experiment and Southeast Asian Replication onlinelibrary.wiley.com/doi/abs/10.111… [1/10]
We were interested in two main issues: (1) how people react to research describing a sex difference, depending on whether the difference favours males or favours females, and (2) how accurately people can predict how the average man and average woman will react. [2/10]
In Study 1, Western participants (N = 492) viewed a fictional popular‐science article describing either a male‐favouring or a female‐favouring sex difference (i.e., men/women draw better; women/men lie more). [3/10]