Problem Solving: Algorithms vs. Heuristics

In this video I explain the difference between an algorithm and a heuristic and provide an example demonstrating why we tend to use heuristics when solving problems. While algorithms provide step-by-step procedures that can guarantee solutions, heuristics are faster and provide shortcuts for getting to solutions, though this has the potential to cause errors. In the next few videos we’ll see examples of heuristics that we tend to use and the potential decision-making errors that they can cause.

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Video Transcript:

Hi, I’m Michael Corayer and this is Psych Exam Review. In this video I want to explain the difference between an algorithm and a heuristic and then provide an example that will hopefully help you to see why it is that we tend to use heuristic.

First, what is an algorithm? Well an algorithm is a step by step procedure for solving a problem. The downside of an algorithm is that it tends to be slow because we have to follow each step. We have to move through the process but on the positive side an algorithm guarantees that we’ll get to the solution. If we can follow all the steps, then we will find the solution to the problem. So an algorithm is guaranteed to work but it’s slow.

What’s a heuristic? Well, a heuristic is sort of a mental shortcut. It’s not a step-by-step procedure and so the downside of a heuristic is, because it’s not a step-by-step procedure it doesn’t guarantee that we’ll actually get to the solution. It might not work so a heuristic is not guaranteed.

We don’t know if it will get us to the correct solution but it’s faster, right? Because it’s a shortcut it skips a lot of the steps and says well these probably aren’t going to get to the solution so I’m just going to skip them. Now it could be the case that those steps would have gotten to the solution or would have gotten to a better solution but the heuristic says I mostly am concerned with getting a quick answer rather than the always correct answer.

Ok, so let’s look at an example of a sort of everyday problem that you might experience and how you would solve it using an algorithm versus using a heuristic. So let’s imagine that I’m in my apartment and I want to go somewhere and so of course I need to take my keys with me and I can’t find them. They’re not on my desk where I usually put them and so I have this problem of how do I find my keys.

Well I know that they’re inside the apartment because I’m inside the apartment and I must have unlocked the door to get in. So one thing that I could do is I could follow an algorithm for solving this problem. I could say okay if the keys are definitely in the apartment somewhere then a step-by-step procedure for finding them will be to start in one corner of the apartment and to slowly look in every single location expanding out from that corner of the apartment until I’ve searched every square inch of the apartment and if I do that it is guaranteed that I will find my keys because they must be in the apartment somewhere.

That approach, that step-by-step procedure will guarantee that I find them but as you can already see it’s going to be slow, right? Because I’m not allowed to skip ahead I have to start in one corner and progress through the entire apartment. Now that’s probably not how you look for your keys if you can’t find them. What do you do instead?

You use a heuristic. You use a shortcut. You say “there’s probably a lot of places that I can just not look in because my keys probably aren’t there.” Now I don’t know that for sure because I don’t know where my keys are but a heuristic that I might use in this approach to solving this problem would be to say “why don’t I look the last place that I remember having them” or maybe I should start by looking in the door, maybe I’ve left them in the door when I unlocked it, right?

Now this doesn’t guarantee that my keys are going to be there but there’s a higher likelihood and it’s going to be faster if I look in the two or three places that my keys are usually found then. I’m probably going to find them. It’s not guaranteed; I might not find my keys in those two or three locations. I might say “okay maybe they’re in the pocket of the pants that I was wearing yesterday or maybe they’re in the door or maybe I set them down on the kitchen table instead of in my bedroom” right?

So what a heuristic does, it says check those places first, take a shortcut. Don’t start looking under the couch, I mean the odds of them being under the couch are probably pretty low. They’re not necessarily zero but they’re low. So start with the places that they might be and then move out from there. Now again, this doesn’t guarantee that I’ll find the keys but it’s going to be a lot faster and maybe I try that and it still doesn’t work. Then maybe eventually I have to resort to my algorithm approach but most of the time we use heuristics.

We have shortcuts that we use that allow us to skip a lot of potentially unnecessary steps. So in the next few videos we’ll look at some other types of heuristics that we use in our decision-making. We’ll also see the situations where they can lead us astray; they can lead us to think that we’ve found the answer when in fact we haven’t or we found an incorrect answer. Ok, I hope you found this helpful, if so, please like the video and subscribe to the channel for more.

Thanks for watching!