That's because there are no aliens shooting back...
It boils down to how much you care about how things are sorted in your bags.
If you don't give a shit then all you have to spend time on in the bagging side of things is being careful placing in the bag products which are in glass containers (to avoid breaking them) and the rest you just drop in the bag. If you've essentially trained yourself to know the side of each product were the barcode is and the scanner is a front-and-bottom double scanner (same as cashiers) you'll be doing near cashier speeds at scanning, In that case and as you pointed out, there being more self-service tills means that if everybody was like you (i.e. don't care much about how their bags are organized, and like to optimize their own checkout speeds) then self-service tills would be faster.
Personally because I do a big weekly shopping and walk or cycle home from it, I actually have to have some organization in my shopping bags, and my bagging speed just about keeps up with the scanning speed of the cashier as long as I've ordered stuff properly in the conveyor belt that goes to the cashier.
As for multitasking, your example is like apples to oranges relative to mine - chewing is literally instinctive (requires no thinking and in fact if you try and think the steps of your chewing, it will be way slower), which is not at all comparable with my example were you have to look at things in different places (which you can't do at the same time because they're different places and you only have one set of eyes) and have to actually make a decision on the bagging side (i.e. "were shall I put this").
Also you seem to not know what an Assembly Line is - this stuff is totally independent of automation (it predates it, dating back to Henry Ford's time) and it's purely about dividing a complex process into multiple steps and have each person just do one step again and again. Since each individual only does one thing they become very effective at it, plus as they're working in parallel, the whole thing is much faster.
"Scanning & bagging" is naturally dividable because each it's own "attention + decision + movement" block.
But yeah, I agree that those systems you mentioned were people just scan things with a portable scanner as they pick them up from the shelves are much faster than manual cashiers because the scanning happens during shopping (there are also other systems were stuff is scanned all at once without having to taking out from the bag, thanks to RFID tags on the products, which are also much faster).
The problem is that the vast majority of self-checkout systems I've seen out there in two different countries are crappy little checkout tills with only room for a single bag, having a non-standardized UI (so, different in different stores) and a shit scanner (either a handheld one or a single-side scanner).
Rather than redoing the whole process to use the possibilities associated with the customer registering themselves the products they buy (as your example "scan the items when you pick them up from the shelves" does), the vast majority of self-checkout "solutions" out there just make the customer do the checkout in the same way as the cashier did, only with inferior tools than the cashier had (less space, less comfort, worse scanners) - so all they do is replace a professional with a free (for the store) amateur rather than make the whole process more convenient.
These "checkout just like a cashier but in a crappy station" self-checkout systems are just about ok for somebody familiar with computers who just wants to check out a handful of products, but are problematic when the store has, for example old people doing self-checkout of their weekly shopping.
In the real world not everybody is like you and when there are no cashier checkouts available, these self-checkouts which are really just inferior versions of cashier tills tend to end up with old people, computer illiterate people, people who need to pack their bags in a certain way and people with lots of shopping gumming up the system because they're way slower than cashiers, at which point you lost the speed gains from having more self-checkouts than you had cashiers and the self-checkout tills end up with queues just like the cashier tills used to have. If you have mixed systems, then people who would be much slower if doing self-checkout will go to the cashiers and the rest can go to the self-checkouts, but the ratio of one to the other needs to be properly balanced (and I've seen several cases of it not properly balanced)
Read what I wrote:
unless you’re just dropping it there without looking
The only way you can just scan and put it in the bag in one movement is like cashiers do it - pass it in front of the scanner with the barcode facing it, them just let go of it, all as one movement.
If you're actually placing it in a specific position in a specific bag you have look at it, pick it up, pass it in front of the scanner, look at where you're going to place it and place it.
The last two steps are additional to what a cashier does around here (were they don't do bagging) hence the process is slower if a single person is doing all those steps rather than just the first 3, and that won't change no matter how elitez your unpaid cashier skillz are.
This is seriously basic stuff and the principle behind Industrial Assembly Lines.
But, hey, if you're happy doing it that way, good for you.
From what I've seen (in two different countries, so it's probably not something specific about the way people are used to do something in a certain country), it mainly depends on the kind of store.
In supermarket type stores (were people, including families and old people, go buy a whole week worth of shopping) self-checkout makes things worse, especially if it's in a country were there's some kind of obligation to check somebody's age when selling alcoholic drinks (because the person who is overseeing a whole lot of self-checkouts has to come around and pass their card to confirm your age has been checked, so you generally have to wait for them, especially if they're helping somebody out).
Those tiny tills that replaced the big manned tills are hugely impractical for people buying lots of stuff and you loose the time saving in the long manned tills which comes from people moving their stuff from the shopping cart to the conveyor belt whilst the person in front of them is being served.
In IKEA stores, were most of what people buy are big packages, self-checkouts seem to slow things down a bit, or at best are neutral, possibly because the space per till is still the same so they're not really adding any more tills by replacing tills with cashiers with self-checkouts hence the loss of speed from having an amateur (the customer) do the checkout is not made up for there being more open tills.
Were I've seen it improve service speed and reduce queues is in small stores were people are just buying a handful of things. This also includes mini-market type stores in inner cities were people tend to go often during the week and buy just a few things like bread and milk.
I've also seen it work in a big surface hardware store, possibly because they still had 1 long cashier till for people who were checking out big items and replaced the other 5 cashier tills with about 10 self-checkouts and most people just bought a handful of small things which are fast to checkout in the self-checkouts.
Correct, which is why no matter how fast you are at the checkout part it's still going to be slower, especially if you're trying to bag things in any way other than "dump stuff into bag as fast as possible" - you can't both be scanning an item and putting an item on the bag at the same time unless you're just dropping it there without looking (which is a problem if anything you're buying is in a glass bottle or jar).
Cashiers are at minimum twice as fast as customers mainly because after doing it for a while they start knowing were the bar codes are in most products and don't have to look around for them, know which are the awkward things to scan and how to do it, and are so used to the layout and sequence of the screens that they just go through them naturally.
You simply can't be as fast at doing something you do once in a while, as somebody who spends hours every day doing it.
Also were I live the cashier doesn't do bagging, the customer does, so whilst in a self-service checkout you're doing both scanning and bagging, with a cashier they're doing the scanning and you're doing the bagging which also makes the whole thing much faster even if you're making sure things are bagged the way you want it (for example, having all cold things in the same bag) because you can focus on bagging.
As for the lines being non-existent in self-service, that's not quite so simple a judgement as it seems:
- First, I noticed that in stores where they introduced self-service checkout they invariably reduced the number of people manning the other checkouts in order to "induce" customers to use the self-checkout (because "the lines are usually nonexistent compared to a cashier").
- Second, once a store has fully transited to only self-checkout, you get lines at the self-checkout, mainly because as I pointed out above, customers are way slower at doing the checkout themselves than cashiers so even though there are more self-checkout tills that there were tills with cashiers before, people take longer to go through them, especially when they have lots of things to checkout, so effectively each self-checkout till has less capacity than a cashier till.
That said, self-checkout is faster for customers in stores with mixed systems (both self-checkout and cashiers) if you have only a few things to checkout.
The sheer perfidy of the Norwegians, with their dastardly scheme to lure researchers away from US universities ... by not treating them like shit.
From my own impression as a member of a small political party in my own country who joined not out of tribalism but simply because they seemed to mostly want the same things as I do, party members live in a bubble of people who are heavilly into politics and understand the importance of politics, whilst the leadership specifically in addition to this are also mostly surrounded by generally unquestioningly hero worship from the common party members plus they tend to have quite limited life experience outside the party as they've joined it as young adults (maybe when they were at university and involved in student movements) and it and its internal environment have always been a large part of their lives.
Those people usually see the supporters of their political adversaries in the same way as fans of a sports club see fans of other clubs, and don't really "get" the point of view of people who don't vote at all.
Carbon atom after millions of years of existence and countless light-years of travelling, having ended up as part of Elon Musk's body:
- "Shit!"
I think people are mainly driver by the tabu against eating human meat rather than any kind of proper thinking about it, but the tabu itself probably came to be because people kept getting sick when they ate human meat but not when they ate other meats.
You see a lot of that kind of thing in other tabus, for example the ones against incest (inbreeding tends to produce offspring with health problems) or handling feces (because the bacteria in feces tend to cause disease much more than the bacteria in things like dirt).
I read it as meaning:
- "Just because two sides are fighting doesn't mean you have to pick one".
I started programming as a kid way back in the ZX Spectrum days, and that one had even less memory than that.
You can do a surprising large amount of functionality if you're hand-coding assembly (I actually made a mine-sweeper clone for the Spectrum like that).
Even nowadays, there is the whole domain of microcontrollers, some of which are insanelly tiny (for example, the ATTiny202 which has 2KB flash and 128 Bytes of RAM) and you can do a surprising amount of functionality even in C since modern C compilers are extremelly efficient.
(That said, that 202 is the extreme low end and barelly useful, but I do have an automated plant watering system I designed - complete with low battery detection and signalling - running on an ATTiny45, an older chip with twice as much flash and RAM).
In my experience, if there is no UI on a screen (graphical elements tend to use quite a bit of memory plus if you're doing animation you need an in-memory buffer the size of the video memory to get double-buffering for smoothness and just that buffer can add up a lot of memory depending on resolution and bytes per pixel), using a compiled language which can optimize for size (like C) and not dragging in a ton of oversized libraries as dependencies, you can do a ton of functionality in very little memory - there are quite complex functional elements out there (like full TCP/IP stacks) that fit in a few KB of memory.