Personality traits are highly heritable and not very malleable/depend on the early environment. Indeed more experience reduces personality:
Decades of research have shown that about half of individual differences in personality traits is heritable. Recent studies have reported that heritability is not fixed, but instead decreases across the life span. [...] For most traits, findings provided evidence for an increasing relative importance of life experiences contributing to personality differences across the life span.
I don’t think this disproves shard theory. I think that differences in small children’s attention or emotional regulation levels lead to these differences. Shards will form around things that happen reliably in contexts created by the emotional behaviors or the objects of attention. Later on, with more context and abstraction, some of these shards may coalesce or be outbid by more generally adaptive shards.
(Note that ‘life experiences’ here is being used in the (misleading to laymen) technical sense of ‘non shared-environment’: all variance on the raw measurement which cannot be ascribed to either genetic variance at conception or within-family shared-across-all-siblings influences. So ‘life experience’ includes not just that rousing pep talk your coach gave you in highschool you never forgot, which is probably the sort of thing you are thinking of when you read the phrase ‘life experiences’, but also that personality item question you misunderstood due to outdated wording & answered the wrong way, and that ear infection as a 6 month old baby that set up the trigger for an autoimmune disorder 50 years later, and that A/B test on Facebook which showed you the wrong job ad, and that gamma ray which mutated a critical neuron at age 35 & gave you brain cancer & made you misanthropic, and… If you are unsure if ‘non shared-environment’ is being used in a meaningful way, simply try swapping in various contributors to non shared-environment like ‘somatic mutations during the first trimester’ and see how sensible the claim remains: sometimes you’ll get something absurd like “the decrease of heritability and increasing importance of somatic mutations during the first trimester over the course of a lifetime proves we have free will”.)
Personality traits are highly heritable and not very malleable/depend on the early environment. Indeed more experience reduces personality:
How Genetic and Environmental Variance in Personality Traits Shift Across the Life Span: Evidence From a Cross-National Twin Study (just add “gwern” to your heritability Google search)
I don’t think this disproves shard theory. I think that differences in small children’s attention or emotional regulation levels lead to these differences. Shards will form around things that happen reliably in contexts created by the emotional behaviors or the objects of attention. Later on, with more context and abstraction, some of these shards may coalesce or be outbid by more generally adaptive shards.
ADDED: Hm, it seems you have seen The heritability of human values: A behavior genetic critique of Shard Theory which has much more of this.
(Note that ‘life experiences’ here is being used in the (misleading to laymen) technical sense of ‘non shared-environment’: all variance on the raw measurement which cannot be ascribed to either genetic variance at conception or within-family shared-across-all-siblings influences. So ‘life experience’ includes not just that rousing pep talk your coach gave you in highschool you never forgot, which is probably the sort of thing you are thinking of when you read the phrase ‘life experiences’, but also that personality item question you misunderstood due to outdated wording & answered the wrong way, and that ear infection as a 6 month old baby that set up the trigger for an autoimmune disorder 50 years later, and that A/B test on Facebook which showed you the wrong job ad, and that gamma ray which mutated a critical neuron at age 35 & gave you brain cancer & made you misanthropic, and… If you are unsure if ‘non shared-environment’ is being used in a meaningful way, simply try swapping in various contributors to non shared-environment like ‘somatic mutations during the first trimester’ and see how sensible the claim remains: sometimes you’ll get something absurd like “the decrease of heritability and increasing importance of somatic mutations during the first trimester over the course of a lifetime proves we have free will”.)