Did you have your eyes on the attacker as the ball was kicked though?
Uh-oh - you just disputed cognition with a psychology student!!
The human brain is like a computer, and it prioritises information based on what it thinks is important, among other things. Do you remember your first games in the middle or on the line? How hard did you have to think about basic things - like which hand to hold the flag in? What about making decisions as an AR? Or even as a ref? Were you a bit slower for some decisions as you were trying to remember if it's a foul, if it's a DFK or IFK, what law 12 says, which team is going which way, and how else you should react?
As an AR, most of the mechanics - the footwork, the flagwork, moving the flag from hand to hand, the checking of the 2nd last defender, the scanning of the field, and considering the issues of teamwork with the referee - all of these require conscious thought. Valuable processing space. If you're spending processing power on these things than it slows down your decision making processes. If you're distracted by thinking about your role as an AR you're not used to, the position you should be in, whether you should be side-on or facing the field, which hand to raise the flag in ,whether you've 'waited and seen' correctly, and whether you should flag or has the ref seen it?, then these are all distracting from your actual decision making processes. You'll still make the decision, but not as fast. And with so many distractions, you're more likely to get it wrong given that, as an AR, incredibly fast processing of multiple sources of different types of information is crucial to the role
As you get more experienced, a lot of that starts happening automatically. So things like which hand to hold the flag or raise it? That's starting to happen automatically, freeing up a bit more processing power.
What that means is when you have somebody who isn't used to being an AR, don't expect their decisions to be as fast as a neutral AR. It's on you, as the referee, to realise this and adapt. They're not only in an unfamiliar role but it's a role that they're not as highly engaged with as you are as refereeing. As a ref in the middle you are multitasking, but you learn that skill and your mind adapts to thinking in that fashion. You can successfully think about where the ball is going, where the attacker is, where his teammates are, where the defenders are, whether that defender looks like he's going to break his kneecaps, whether the attacker handled it as he stopped it, where you need to run to because X will happen, actually, let's run over there instead because I think Y will happen, but lets hold back slightly because there's a fair chance Z will happen, as well as what your AR is doing. You can pretty successfully think about that all at once because a lot of it becomes fairly reflexive thinking and your mind is prioritising the tasks like your computer's CPU is prioritising requests. Your poor club AR? Not only is he not used to the role, but he doesn't know all of that extra stuff, he only has a vague idea that he has a job to do, doesn't really know what the rules are but he's trying to think about them and the job and he doesn't want to be there and he's not trying to better himself - meaning literally everything he does is requiring conscious, deliberate though. AND because he's not thinking like a referee he's also distracted by watching the game!
There are stacks of psychology studies conducted on the effects of distractor tasks and familiarity on decision making processes.
Even with neutral AR's, they may not be responding as fast as you're looking. Especially when it's something like a lone striker receiving the ball unchallanged and it's not critical when you take your eyes off play, maybe look a moment later. Give your AR an extra moment or two.
Heck, sometimes as a ref you actually need to think for a moment before you make a decision. Sometimes as an AR it's not a bad thing to take a moment on the really close offsides. Maybe. Could probably start a whole other discussion on whether your reflexive decisions as an AR can lead you astray!
