How about the fact that people mature and some sophomoric (i.e., moronic, blue, obscene) humor does not appeal or seems a bit repulsive.
Not to mention the fact that most 65 or 70 year old have no awareness of contemporary cultural drift/evolution on terms and meanings... How many older people understand what PHAT or cheddar means? [Assuming all of the older people in the study did not have dementia!]
Similar conclusions were drawn about certain minorities and their mental capability because they had not been exposed to certain things... The conclusion... they are slower and dumber!
I can understand how a few nitwits (desperate university researchers) drawing invalid conclusions related to cause and effect would publish this dribble. It sounds like a publish or perish (feeling the pressure) subject from some academic that is digging for federal funding on a grant. They may think they are researchers... They are
PHDs (Piled High and Deep).