Thursday, Sep 8th
Monday, Sep 12th

Psychology: Human Tendencies in DFS


I want to start our discussion on psychology with a further dive into common knowledge. Common knowledge in a game of competing wills is the assumption that I know the same information as my opponent knows, and my opponent knows the same information as me, and so on and so forth down the line of prospective game participants. I’ve referred to this sentiment previously, but more so in the context of contest rules, payout tables, and other clear constraints, like a salary cap.

Let’s now introduce similar concepts, with a slight, and massively important, twist. Andrew M. Colman and Eva M. Krockow proposed this slight variant to common knowledge in their paper “Game Theory and Psychology,” which was released in the 2017 edition of the Oxford Bibliographies. They write, “The concept of common knowledge was introduced into game theory by Lewis 1969 and was later formalized by Aumann 1976. It needs to be distinguished carefully from general knowledge or mutual knowledge. It is possible for all members of a group to know something without it being common knowledge in the group, and from a strategic point of view this can make a big difference. This is not easy to grasp…Thomas, et al. 2014 discusses common knowledge in relation to the bystander effect, a social psychological phenomenon according to which people are less likely to intervene in an emergency — to help a person in distress, for example — when other people are present than when they are alone.”

Let’s break that down!

They describe a scenario in which all members of a group, or game or contest or draft, know a piece of information but it falls outside the realm of the accepted common knowledge. How can this be? Well, what if there are members in the group that know said piece of information but do not know (or care to accept) whether or not the other members know the same piece of information? You can see how that could affect basic strategic elements when formulating an optimal way of attacking a game. Gone are the days where a large edge could be gained in DFS simply by being the most up-to-date on news around the league. Everyone is keeping up with injuries, everyone is tracking roster movements, and everyone knows what the weather will be on game day. Accept this as common knowledge now. Remove the guise of this information falling into the realm of general knowledge or mutual knowledge. There is no edge in DFS here.

“But…Hilow, you said there would be an edge!”

The latter portion of their quote describes the “bystander effect,” where humans tend to react less, or, in some instances, slower to an emergency when there are more people present. Sound familiar? Bingo! It’s group think in a fantasy setting! You’ve probably heard me reference the fact that I am constantly looking for reasons why a public assertion is false rather than accepting it as truth. This is the reason for that. It is human nature to cling to the crowd when put in uncomfortable situations (DFS is uncomfortable as hell for humans — we are literally placing money on guesses). Tools like Twitter, group chats, and Discord only deepen this urge, as well as outside indicators like prop lines, Vegas team totals, the multitude of analysts in the industry, and projected ownership numbers. Many probably thought I was crazy for playing an entire NFL DFS season without looking at projected ownership numbers until Saturday evening. This is the prevailing reason why I did that last season (and I’ll answer the question now: yes, that was entirely experimental for me last season; it was also largely a success!). For all these reasons, I propose a challenge to you: when sifting through information this fantasy season, take the information in, digest it, and then poke holes in it. Find all the reasons why an assertion should not be the case. And if you can’t find any, search for ways to leverage that area of general or mutual knowledge.

As social sciences and mathematics have grown and evolved, additions to legacy Game Theory have arisen. For example, only recently has the premise of “transient preferences” been introduced. Transient preferences simply means that human behavior, habits, and goals are a constantly moving target easily affected by outside influence. From the perspective of a fantasy analyst, this ties directly into recency bias and favoring of one position over the rest. Let’s take best ball draft theory as an example (I know, I know, this is a DFS course, but this will highlight what is important here). Last season, those who were proponents of the “zero-RB” draft model were publicly ridiculed as borderline insane due to the lack of depth of workhorse running backs in the NFL. This year, “zero-RB” is all the rage. Is this the case because the consensus “1.01 pick” was lost for the season, or because an undrafted free agent finished as an RB1? Entirely likely, in my opinion. Guess who was overweight “zero-RB” roster construction last year and is underweight this year? Yeah, this guy. The problem arises from the depths of transient preferences and gains root with the psychological aspects of recency biases and group think mentality.

We see the same tendencies develop throughout the season through the lens of DFS, just on a shorter timeline. Pay close attention to what happens to high priced running back ownership the week after one or two of them (by them I mean running backs priced above $8,000 on Draftkings) returns value at high ownership. The following week, people will be doing what they can to jam high priced running backs in and figure out the rest. The names are quite literally irrelevant. It’s a simple psychological and mental break. People see one thing work (or not work) and want to replicate it (or shy away from it) in the future. And when they disappoint, the opposite will happen. People will now be looking for the mid-range and low-priced running backs to build around. 

99% of fantasy footballers operate in the comfort of the known. They (yes, they, not us) make assumptions about the future based on the past.

Other areas of emphasis in psychological strategy include coaching tendencies (#coachingtendenciesmatter), injury or personnel-driven changes to these tendencies (Cleveland Browns from early 2020 to late 2020, Buffalo Bills 2020, and Pittsburgh Steelers 2020 are all prime examples of what I mean by this), and scheme adjustments. 99% of fantasy footballers operate in the comfort of the known. They (yes, they, not us) make assumptions about the future based on the past. Thusly, we can safely assume that the field is slow to react to changes, both from season to season and week to week. This would fall into the category of general knowledge, as every member of the group (a DFS contest, in this example) knows the injury happened and every member knows every other member knows the injury happened, or every member knows team X has a new offensive coordinator and every member knows every other member knows team X has a new offensive coordinator, but every member of the group (DFS contest) does not take a forward-thinking approach based on these knowns. So, every member of a DFS contest has the same information regarding a potential philosophical offensive shift and everyone knows all others have this information (common knowledge), yet the largest edge (how we can expect the offense to operate in the near future moving forward) is either known by a small percentage of players or is not accepted as common knowledge. This again drives us back to the psychological desires for human beings to seek comfort in the known.


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