Interesting couple questions.
I know there's the common belief that the "baby" gets more attention. The guys on Duck Dynasty heck the hell out of their youngest brother because he's pampered all the time.
I'm not sure you can get a direct answer to it. From a siblings perspective I would guess most older kids do feel their younger siblings are given more attention but that's likely because they weren't old enough to remember how much attention they received as a younger child (provided we're talking about young kids.....say an 6 year old with a 1 year old sibling).
I'm sure if mom had to come in and wipe the 6 year old's butt for him, bathe him, dress him, and do all the other chores associated with small kids that he'd feel like he's getting more attention.
Do younger kids get attention because they need it more? Smaller, more likely to get hurt both physically when compared to the older kids who are doing the same activities. More likely to run to mom when they are hurt physically or emotionally. Likely some age range where the smaller kid cannot do the same activities so he's left at home with the parents. Older kid is out playing and isn't around to even get attention.
Who knows. I've heard of beliefs that say younger gets more or older gets more. Guess why being the middle sucks. You hit that prime spot where the youngest is too young to be as independent so attention is given simply out of necessity and your older sibling is at an age where certain privileges are starting to be bestowed on them. Later curfew, more independence, involvement in activities probably higher just based on opportunity. Involvement comes with expenses......"you bought him a new item, why not me".
From all accounts my mom watched me like a hawk when I was really young. She even went as far as preventing my uncles from all their hazing rituals that all of my cousins were tormented with at a younger age. Anyone ever been "Snipe Hunting"? They built that up for years because my mom wouldn't let me go. By the time she did, the whole idea of it was kind of busted because I was old enough to catch on in a timely manner. My brother on the other hand didn't get that nearly as much.......certainly wasn't protected from my razzing.
I'd be interested to see your conclusions.