The mother's 1980s mop of hair is just atrocious, and I say this as someone with curly hair myself. I've seen plenty of pictures, movies, etc - including of my own family - of women in the late 1930s and early 40s, and they did not wear their hair like that. Where was the research from the hair and makeup people?
As a kid I always thought it looked like she is so frazzled by running her house and dealing with 2 kids and her husband, that she never had time to fix her hair.
This is, unfortunately, a common problem in films, particularly historical ones made by people who don't care about making things look authentic. You end up with actors refusing to change their hair because they went through all this trouble of making it look good for THE TIME, and refuse to re-style it for their character. Either that, or nobody involved in the movie has a CLUE how the hair SHOULD look for the time period, so they're all shooting the story in ignorance. The end result is a film that seems to nod more towards the time it was made, rather than the time period in the actual story. It causes a lot of confusion for people who love historical flicks, because you've got people with late 20th century hair or mixed-up clothing pieces, and yet the story is supposed to take place before such hairstyles were ever worn.
That's why I was confused as a kid (in the 90s) when watching this. I had no idea for a while, why they had such primitive desks in the classrooms, or why the phones looked so old, why there were no computers in the house, why they were listening to radio shows instead of tv, or why the cars looked weird. I actually assumed the story took place in the 80s or 90s, and yet something didn't add up.
It took me years to figure out that this story was a flashback, probably narrated by a fat old man remembering his childhood in the 1940s during Christmas, and the big confusing part was that mom's hair just SCREAMS 1980s.
I'm glad I found your post, because I thought I might be the only person in the western hemisphere who was confused about the era the first time I saw this movie, and all because of the mother's very 1980s look!!
I came late to knowing about this movie, only catching it for the first time in the 90s, and when I was already an adult. Even as an adult I wasn't sure about the era and I wondered why there seemed to be a mix of old-fashioned house and modern looking wife's hair-do.
I even decided it must be one of those deliberately ambiguous films where the makers are actually going for "no particular time-period" and a mix of everything, to make it "timeless." A bit like "It Follows" features set dressing and props that seem to be from all over the time eras.
I think Melinda Dillon's hair being completely untouched by a stylist with the tiniest bit of attention to era is one of the most distracting things in this movie.
I'm not saying no woman in the 40s had curly hair or frizzy hair that may have ended up looking like this, but even then, when I've seen all kinds of photos of people from that era, or actual movies from that time, they seemed to try to make some element of their curly hair look like the fashion of the times, while Dillon's looked very markedly "Eighties perm."