>>65527256The actual science? Fine.
"Cuteness" is based off a phenomenon called neoteny, which is specifically related to retenance of childish properties. You don't have to fuck something to find it cute (see: children/animals ) For men, neoteny is a sexually advantagous trait in females, since a female never develops full systematizing capability and retains a childish worldview ("feels") specifically so she can emphasize with and act in stead of her children in a way often struggle with.
A reduction of language is a sign of childishness, therefore it is neotenicnand therefore cute. The Japanese language is specifically favorable to this because it's relatively recent adoption of the roman alphabet ("romaji") is more recent and therefore Japanese grammar and pronounciation isn't as distorted by accent as say a middle-easterners. This allows it to better mimic the developmental way that children of a native English-speaking country would talk.
Other than that there's a couple of associative things that help it along: The Japanese cultural norm of using onomatopeias, cultural preservation of cuteness in women and children as well as anime (an artstyle defined by attributing neotenic facial features and proportions to adults) all aid in making Japanese engrish sound cute.