Self Checkout Machines: An Analysis of User Interaction
storyboarding cover

In this project for CSCI 1300: User Interfaces and User Experiences, taught by Jeff Huang, we were asked to choose one interface we have interacted with and analyzing it using concepts of mental models and personas. My partner for this project was Kate Atschinow, and we chose to analyze the self checkout machine.

The self checkout machine is an alternative for customers to purchase items as opposed to going up to a traditional cashier. It helps to shorten checkout lanes and reduce wait times. Customers scan their items and pay using their preferred method of payment, usually cash or credit, but the machines at the local CVS do not accept cash. The self checkout machine contains four main components: the touchscreen display, item scanner, credit card reader, and bagging area. Customers scan each item barcode, place the item in the bag, which is verified by weight against previously stored information, press the appropriate buttons touchscreen display, and then make their payment via their preferred method.
vector image of checkout machine
Behavioral Observation
While observing customers, we noticed that the line for the self checkout was much longer than that for the cashier. After one customer finished bagging and walked away, the next person in line would walk up to the machine. For the most part, users were able to go through the checkout process efficiently. We observed customers’ interactions with using the self checkout machine and came up with a list of observations about customer behavior and attitudes while using self checkout.
  • One customer had to request for help when the machine was unable to process one of his items, and he had to wait around until a staff member came to help him.
  • Many customers went up to the self checkout with a friend and the friend would sometimes assist in pressing the correct buttons.
  • Several customers clicked the “Skip Bagging” option, especially when their items were small, and did not place their items on the scale.

User Interviews
Do you prefer self checkout or going to the cashier?
    User 1: I prefer self checkout.
    User 2: Self checkout
What are some reasons you prefer one over the other?
    User 1: Because I don’t want to interact with the cashier, and I feel like it (the cashier) definitely takes more time.
    User 2: The self-checkout usually has a faster line and I don’t have to talk to anyone.
How likely are you to use the self checkout machine as opposed to going to the cashier?
    User 1: I’ll use the self checkout all the time unless I have too many items or there’s a huge line for the self checkout
    User 2: Very likely. I only use the cashier when I’m using cash or a machine isn’t working.
What do you think can be improved with the user interface of the self checkout machine?
    User 1: I feel like it’s already pretty straight forward but sometimes the scanning is too sensitive so then it’ll scan your item twice. And then other times if you have too light of an object, like let’s say you bought nail polish and you put it down in the bag it won’t detect that you have it in the bag so it’ll keep waiting for you to put it in the bag. But then you can just say “skip bagging” and then scan the next item.
    User 2: After I scan an item it doesn’t always register when I put it down in a bag. I’ve also had problems with it reading my credit card when I put the chip in. Also sometimes it takes multiple tries for the scanner to scan my item.
Are there any parts of the interface that you find confusing?
    User 1: No, but also I’m not someone who uses coupons. But if I were to have coupons I would be confused as to how to use it. Normally it’s pretty straight forward. I just use my credit card.
    User 2: When I bring my own bag or don’t need a bag sometimes I don’t know if I should press the button for using my own bag or skip bagging because I have had to press both before.
If you could change any features of the design, how would you?
    User 1: I think the Amazon concept is nice, where you can just take the item and leave. It’s convenient that it’s checkout free and you just get charged through your Amazon account. But some people think it feels like shoplifting.
    User 2: I would make it more clear exactly where you should put the item you’re scanning so you don’t have to just wave it around. Also make it easier to choose your own bag or skip bagging.
How does this self checkout machine compare to self checkout machines you have used in other stores?
    User 1: The only other one I’ve used is Target and it’s exactly the same. There’s no discrepancy. I’m pretty sure it’s the same exact interface as well.
    User 2: The only difference I’ve noticed is that the other ones have a security monitor which doesn’t necessarily affect my experience with it.

Most people that we observed using the self checkout machine were college students, mostly because CVS is located right by Brown University. This particular sample is not a good representation of the range of people that may be using self checkout machines in other CVS stores, where there are likely to be more customers who are older. Older customers may have less experience with technology and find it more confusing than the population we observed. However, the people we observed were representative of the people who frequent the CVS on Thayer Street. We went on different times of the day, and as expected, mostly saw students along with a few Providence residents who are not students.

Mental Models and Personas
Mental Model #1:
The user selects “Use my own bag” and then places the item in their reusable bag after scanning. However, an error occurs and the machine does not let them scan their next item. The user does not press the “Skip Bagging” option because they want to place their items in a bag. They cannot figure out what is going wrong, so they press “Request Help”. The user’s mental model blocks the user from identifying a way to resolving the issue, which is likely to have been caused by the weight detector not being able to detect the item on the scale. The user does not understand that “skip bagging” would help them bypass the weight detector error, and they do not click on it because they want to place their items in a bag. Because of this, the user becomes stressed because they are not able to identify why they cannot use their reusable bag.
first mental model persona
Mental Model #2:
The user scans the item and places it in the plastic bag. The weight detector does not detect that an item has been placed there, and the user is not able to scan the next item. They notice that there is a “Skip Bagging” option so they press it, thinking that the items are small enough to carry without a bag and that maybe the button will help skip past the weight detector not being able to detect the item and override the scale’s inability to detect items whose weights are out of range. They are then able to move onto scanning their next item. The user’s mental model of the self checkout machine was that the “skip bagging” option would allow them to bypass the weight detector, so they were able to resolve their issue and purchase their item quickly, though initially with slight confusion due to not being able to scan the next item.
second mental model persona
Rushed Robert is a student at Brown University who likes to use his time efficiently. He always looks for a way to do things as quickly as possible so he can keep up with his busy lifestyle. He is constantly juggling his work from his engineering classes, soccer practice, and hanging out with his friends. With the goal of saving time, he chooses self checkout because the line is shorter. He uses the plastic bags for the sake of convenience because he doesn’t want to have to carry around a reusable bag on top of his athletic gear. His ability to problem solve allows him to identify the cause of the machine malfunction. Rushed Robert is like many students and wants to make his purchases and leave the store as quickly as possible with minimal interactions with other people in the store.

Throughout this process of conducting behavioral observations and user interviews, we were able to gauge customers’ general feelings self-checkout. Based on our observations, more customers preferred using the self-checkout machine. Though it seemed to be the more popular option for purchasing items as compared to going up to an employee, there were also issues that customers faced such as the machine not being able to detect scanned items that were outside of the weight range. It was helpful to think of mental models and personas to better understand how different users might feel about the process of self-checkout and how they reacted when an issue occurred.

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