Chocolate and Gold Coins

Friday, March 10, 2006

Vending Machines and Rationality

Sunil has a hilarious post about his confrontation with a vending machine. It made me recall some incidents I have had with vending machines.

How often have you seen this: you go to the vending machine and you see a snack dangling by one corner on a hook. You know that if you pay 60 cents, you could get two snacks for the price of one. But you have to wonder why the previous customer left the snack just dangling like that. Here are some possibilities:

1. She just put her last 60 cents in the machine, she had to abandon her hope for a snack
2. She used to assume that the probability of getting a snack was 100% if she placed the coins in the machine. Now that she sees that it clearly is less than 100% she Bayesian updates her prior and decides that now the probability is closer to 50%. Buying candy from a vending machine is no longer cost effective at this low payout.
3. She went to the vending machine out of combination of hunger and moral weakness. She knows she should not be snacking. When she sees the snack dangling from a hook, she sees that as an omen and repents.
4. Her preferences are really variable over time. By the time she sees the snack is just dangling from a hook, she wants something else and ends up buying another snack instead.
5. She was willing to pay 60 cents for one snack but not 120 cents for two. So she decides to cut her losses and go back to her office.
6. She only wants the snack that she paid for and if she tries to buy it again, she will be stuck getting two and eating two, (since she cannot bear to throw food away) and she knows that this would be wrong.

Some of these arguments are reasonable and some are just plain stupid. Which ones do you think are reasonable? And do you think that the average person who leaves the snack on the hook does so for reasonable reasons or stupid reasons?


  • hehe........
    i would vote for the first one.....i'm usually digging out the last bit of change in my wallet for the machine. If it fails, i have no change left.

    (thanks for the link too :-)

    By Blogger Sunil, at 1:20 PM  

  • #1 for me too. Else, I can just keep it in my office to consume it at a later time (aka 5 minutes from now).

    By Blogger Niket, at 4:09 PM  

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