John's situation is unique is many, many ways. So this is a messy summery of little pieces of them that that effect their personality + more details about what Benny's attack changed.
I've never really detailed how exactly Benny's attack affected John, outside of "it granted them human intelligence" or "sapience"(which I realize had a different definition than I thought), while that was... a okay way to summarize it, it's not really a perfect description or all that accurate. They didn't "become smarter" from it or anything like that.
In my headcanons, lakelurks already are about as smart as humans (3-6 int), they just don't have society due to their typical antisocial behavior; which means they don't have cumulative knowledge as a species, and it's much more difficult for them to develop technologically or develop their own language despite their intelligence.
They often make tools and such, but since they don't teach their young anything, every lakelurk is starting from scratch and has to figure out and learn and solve everything on their own.
HC wise, lakelurks were also intentionally created by humans (similar to how deathclaws were made!) And from… their general appearance, it can be assumed they are some mix of person, lizard, turtle, and fish made using FEV. But from their general body shape, I always assumed human was a large percentage. Their brains are very similar if not nearly identical to a human's. I often lump them in moreso to FEV affected humans like super mutants or Harold or mole miners, but lakelurks don't have any memory of being human to work off of, because it was their ancestors decades before that mutated, and they were simply born like this.
Theoretically, John (or any lakelurk) COULD HAVE learned english and all the things they do now about humans, but… they would've been far less receptive. I don't think the species' antisocialness is 100% a hardwired trait, it just naturally develops due to their lifestyle. John also isn't even the smartest lakelurk out there!
The injury from Benny mostly affected their frontal lobe; which effects a lot of things, like personality for example. The extreme change in lifestyle following it also changed them quite a bit, too.
John, I would say, always had a slightly less aggressive/calmer personality than a lot of other Lakelurks. They are also very curious. The injury only really exaggerated/highlighted these traits.
Waking up in recovery, they were very weak and under the care of the Doc. They observed him, and figured that if he wanted to hurt them, he would've done so by now.
I wouldn't say their judgement is impaired, but it has changed. They TYPICALLY don't jump towards aggression nearly as much. It also changed as they grew as a person.
Due to their increased curiosity, they stayed around Doc longer than they technically needed to. Eventually they did discover they that they enjoyed social interactions and relationships. They never had the chance to explore something like it before. Learning to speak/read/etc was really just to sate their rampant curiosity and to further explore new and exciting bonds with people.
Impulse control/attention span was a big change too. Once able to sit in wait for hours to days while hunting, they now struggle to wait for more than a few minutes and become bored much easier. They try to manage this by distracting themself by reading or drawing.
Due to their size/general lack of needing to practice it, Lakelurks typically lack advanced hand-eye coordination skills. John lost what skills they had after the injury and had to relearn a lot while learning to write. It is still something they struggle with and a big reason they prefer alternatives to communicate. They also cannot lockpick things for the life of them. Small muscle spasms also make thing's harder.
They also had some small changes in how they processed sensory input, but the biggest change was a new sensitivity to light, causing headaches. Preferring to travel during the morning and evening + wearing sunglasses or goggles makes this one of easier things to manage.
They struggle to make any verbal sound. This means they cannot do the sound-stun attack other Lakelurks can. Even if this wasn't effected, their vocal cords wouldn't have been capable of producing most sounds necessary for English.
John doesn't clearly remember their life before the injury either, only really a few clear moments and then some things that are only half-there. Small things/details are often forgotten in day-to-day life, so they frequently record things in their Pip-Boy to remember better.
They recognize these changes and do have mixed feelings about them. I think they have a lot of issues with imposter syndrome too. Also it is confusing and strange when your mind suddenly starts working differently than it has your entire life. Interpretating things differently than you always have. They feel very disconnected to who they were before, and that is strange and isolating to them. In the past, they never had such an extreme change in environment that caused them to change fundamentally so much. It's exhausting.
One of the first things they truly learned about humans was their kindness. They lived in Goodsprings for a few months and would've been pretty content living out their life there, helping the locals and exploring surrounding areas. Kindness was strange and surreal and new but oh so wonderful to them.
Most often they helped the Doc. Carrying patients and supplies, maintaining the house, and delivering things for him. Sunny Smiles had a new hunting buddy. Eventually they felt themselves ready to do something independently, and took the opportunity to deliver medicine to a neighboring settlement, Nipton.
They learned about how people can be so unnecessarily cruel first hand when they went into Nipton. Sure, they heard about stuff like it plenty, but never truly experienced it. They were confused and horrified and curious why and how someone could do such terrible things.
Though logically they know they're are people worst than Vulpes, that have done worse, hurt more people, but Vulpes is the first person they truly hated and probably their least favorite person. That is saying a lot, perhaps out of naivety or just plain old optimism, they really do try to see the best in people. Vulpes is someone they can't see anything good in.
Nipton is the reason they went out and explored the Mojave further, not for any concrete reason, it shook just them and their worldview up. They needed a change and they needed to learn more about why people can make such terrible decisions and commit such terrible actions.
A big part of them is that they simply don't know a lot of little things. They know math and can read and such, but don't know a lot of little parts of the human experience. They are eager to learn, though. I struggle to call them "innocent", they aren't, they are just inexperienced with things. They didn't know the difference between coyotes and dogs, what taxes were, or a lot of things people would consider to be common knowledge.
They also struggle with sarcasm and jokes. This perhaps is just me projecting, like with a lot of traits my OCs have.
They don't fit in with lakelurks anymore, but they'll never really fit in with humans either. They try their best to fit in with people and act like a "normal person", but what does that even really mean? Also rampant self worth issues.
They are smart. They struggle to see it or acknowledge this.
I also tried to give them a lot of traits that directly correlate with gameplay mechanics/how the game is typically played.
Anyways there ends my rambles about my zombie courier fev mutant fishperson.
