Being alone or in group has a more prominent impact on *behaviour*, not the thought process; these are different things, not necessarily correlated.
The effect of group membership to individual thought processes is called
groupthink.
How strongly thought processes and behaviour are correlated, is a topic in psychology, and I'm not an expert. What I do know is that
cognitive behavioural psychotherapy uses the connection between the two to improve emotional regulation and coping strategies with many mental health conditions, quite effectively in my own personal case. Because of that and the related research I've read, I do
believe thought processes or cognition in general and behaviour are tightly coupled (so much so that it has been proven statistically that forcing a specific behaviour will slowly change the related thought processes given sufficient repetition), but again, not an expert.
The social pressure that is debated here is about adopting the group's *behaviour* (for whatever reason). It doesn't necessarily imply the person changing their mind or adopting a different line of thought. At least not immediately.
Sure, but we're talking in statistical terms here: what
typically happens.
I know how to understand and empathise people I do not agree with. I practice that quite often, because I like to try and find out the reasons for different opinions and beliefs, by reading and listening to what all kinds of people have to say – including some conspiracy theorists and political pundits. I am often quite sympathetic, too, although I will not tolerate exploitation of others or unfairness. I
participate in such a group, but do not adopt or belong to the group, if that makes sense. So, sure, one isn't Borg-ified by just blending in with some group.
Yet, pick any random group, and check how many only participate, and how many adopt/belong/follow the group body and mind. My current opinion based on observations and discussions with others and their observations, is that
majority follows the group body and mind.
The size of the group is a very interesting factor. I suspect
Dunbar number is key here. It would imply that when group size exceeds 250, its influence on each individual starts statistically decreasing. One exception is a mob that consists of many separate groups with similar purposes/aims/behaviour.
To tie this groupthink strand back to the original topic, Ashton Forbes Over Unity Challenge, I wonder how much of it is due to the groupthink of online communities?
(You could equally call it say an echo chamber effect. I don't think it is by intentional design – definitely not a conspiracy!
–, but appears because the algorithms are designed to keep people
happy and avoid conflicts engaged at minimal moderation cost. Yet, to me, the long-term effect on those participating seems to be the opposite: drives people towards groupthink and simplified worldview, and reduces the interactions between people who have differing opinions and experiences and worldviews. I think that acts as a volume booster for goofballs like over-unity "enthusiasts", and "catches" people who would otherwise not be as easily caught by such ideas.)