Monday, July 19, 2010

Shared Beliefs, Focal Points, and Phone Finding

I lost my phone last Thursday.

Fortunately, I knew exactly where I'd left it. I constantly check the clock on my phone during class to adjust my lecture speed so that I don't spend too much or too little time on any subtopic. Given that I had driven straight home from class, and that I realized I'd left my phone almost immediately upon getting home, I knew it had to be sitting on the podium. But when I returned, it wasn't there.

I figured there were two possibilities:
1. Someone found the phone and decided to keep or sell it.
2. Someone found the phone and attempted to get it back to me.

Obviously, P(1) > 0. There are criminals in the world. However, I reasonably assumed the conditional probability that the person finding my phone was a criminal was quite low. Most likely the person finding my phone would be a college professor, as it was on the podium. There was also a relatively high probability that a student taking summer classes found my phone. Regardless, I'd guess few individuals in these groups are criminals or have access to criminal networks such that reselling the phone would be worth the risk of being caught. There was also a possibility that someone on the cleaning staff located my phone. Now, I'd imagine the probability that cleaners--typically from low-income households--have access to criminal networks would be significantly higher than college professors and students taking summer classes. But the odds that a cleaner found my phone would be low. I teach a morning class and cleaners typically work at night. So scores of people would have to overlook my phone for it to be on the podium when the cleaners arrived in the evening. Hence, I believed P(1) < P(2).

But how would they attempt to get it to me? They did not try to call me. Nor, to my knowledge, did they try to call anyone in my recent calls. Instead, they would likely do what people in our society normally do when the find something that has been lost: drop it off at a lost and found. This is where focal points become important.

Where is the lost and found? As it turns out, there are several options. Here are the most likely:
1. Secretary
2. Campus police
3. Johnson Center Information Desk
4. Student Union Information Desk

A lazy person might just walk over to the secretary in the building where the phone was lost and let her deal with it. But this assumes two things. First, it assumes that the phone finder knows where the secretary is. I am an instructor in that building and (until I actively began looking) I didn't know where her desk was located. Second, it assumes that either (1) I will know to go to the secretary to retrieve my phone or (2) the secretary will know where I'm likely to go and be willing to take the phone there. Note the importance of shared beliefs. The only way this works out is if the phone finder and I or the secretary and I have shared beliefs about what should happen to lost and found phones.

If the secretary option is not particularly salient, perhaps the next option would be the campus police. However, the GMU police station has recently moved from a building relatively close to the class where I lost my phone to the other side of campus. This decreases the likelihood of my phone ending up there for two reasons. First, it requires more effort to get it there than any of the other potentially salient options. Second, given that the change took place recently, it increases the likelihood that either I or the phone finder is not aware of the change and hence decreases the likelihood of a match. Knowing this, even a phone finder aware of the station change might be reluctant to take the phone to the police. Again, note the importance of shared beliefs and knowledge about shared beliefs.

The third option, JC Info desk, has an advantage in that it is right in the center of campus. All the food vendors are located in the JC. Going to any other class or office on campus would likely cause you to walk past the JC. However, the JC is in the opposite direction of the nearest parking lot. So instructors or students showing up for one summer class might have to go out of their way to go to the JC.

The fourth option, the Student Union Info desk, is anything but centrally located and is also off path from the nearest parking lot. While this option might be particularly salient to students, it is not likely to be as salient to instructors. And recall that the phone finder is likely to believe the phone was lost by an instructor since it was on the poduim. Hence, even if it were salient for a student phone finder, the student would have to consider whether it would be salient for me.

So where did the phone finder conclude that I would most likely look for my phone? Well, since I was fortunate enough to retrieve it today, I can tell you. And we can all learn a little something about shared beliefs. Take a guess. The answer is below the fold.



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