What is the hawk-dove game and how does it demonstrate behavioral strategies?

The hawk-dove game is an exercise where players choose between aggressive (hawk) or cooperative (dove) strategies in repeated interactions. Players gain points based on their choice and their partner's choice, with scores determined by a cost-benefit table where B equals four and C equals three. This game models how different behavioral strategies succeed depending on whether interactions occur with the same or different partners.

How does strategy frequency change when playing with a single partner versus multiple partners?

In single-partner games, the dove strategy typically becomes more frequent as players learn cooperative patterns with a familiar opponent. In multiple-partner games, the hawk strategy becomes more frequent because players interact with different opponents each round, reducing incentives for cooperation. These contrasting patterns demonstrate how partner consistency influences the evolution of behavioral strategies.

What defines cheating behavior in the cooperation exercise?

In the cheating and cooperation exercise, a cheater is defined as a person who gives fewer benefits than they receive from their partner. Players exchange colored beads representing benefits without knowing what they will receive, and benefits from different colors are worth twice as much. Tracking cheating frequency across rounds reveals how dishonest behavior affects long-term fitness and cooperation.

How do cooperators and cheaters compare in total benefits received over time?

The experimental hypothesis predicts that cheaters receive fewer benefits over time while cooperators continue providing equal benefits to one another. By graphing the percentage of rounds each player cheated against their final benefit total, students can observe whether cheating or cooperation yields greater fitness. This analysis reveals that sustained cooperation typically outperforms short-term cheating strategies.

What happens to cheater frequency as the number of rounds increases?

Cheater frequency typically declines over successive rounds as partners learn to avoid or punish dishonest players. Graphing the percentage of cheaters against the number of rounds reveals trends showing that cooperative strategies become more common when interactions are repeated. This pattern suggests that strategies favoring cooperation would likely evolve in settings where partners interact repeatedly.

How does changing the cost-benefit values affect which strategy becomes dominant?

By manipulating the values of B and C in the cost-benefit table, students can find the point where the hawk strategy no longer provides an advantage over always choosing dove. Adjusting relative benefit values demonstrates that strategy effectiveness depends on the payoff structure. This exercise shows how ecological or social conditions that alter costs and benefits can shift which behavioral strategy evolves in a population.

Why would a species relying on cooperation benefit from repeated partner interactions?

Species that depend on cooperation benefit from repeated interactions because partners can recognize and reward cooperators while punishing cheaters over time. When interactions are unpredictable or one-time only, selfish strategies gain advantage; but with repeated encounters, cooperative tactics become more profitable. This principle explains why many social species evolve mechanisms to maintain stable partnerships and recognize individual partners.

Group Behavior

Concepts Instructor Prep Student Protocol

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Have you ever wondered why some animals are solitary, while others are social? Let's consider these different hamsters, for example. Syrian Hamsters are territorial, therefore unwilling to share resources. Since they can't tolerate each other well, they will fight others entering their territory, and can injure each other, potentially fatally. On the other hand, Russian Hamsters typically live in small groups, sharing resources, and forming long-lasting bonds, especially with their mating partners.

Speaking of mating, you may have noticed that some animals exhibit something called Polymorphic Mating Systems, meaning that one sex, generally males, develop different phenotypes and mating strategies. In sea lions, for example, males are much bigger and have more powerful jaws and necks than the females. In terms of the different mating strategies, dominant males gather harems of females up on the beach and fight any challengers trying to take their mates. However, some non-dominant males stay in the water around these groups, as a strategy to mate with females who have left the beach temporarily. These distinct behavior strategies can affect an organism's fitness differently, and so one strategy may dominate others in a population over the course of evolution.

Let's look at this more closely. This preferred strategy, here called strategy one, is known as an Evolutionarily Stable Strategy, or ESS, because the payoff is greater than any alternative strategy. Males that employ the less-beneficial strategy two only do so if their risks of fighting to gain a group of females is extremely high and likely to be unsuccessful, perhaps because they are extremely young or very old. To understand how Evolutionarily Stable Strategies like this arise, biologists turn to game theory, which is the study of cooperative and conflict behaviors between individuals, using mathematical models. First, biologists assign benefits and costs to different strategies. Benefits might be gaining control of a resource, like food or mates. Costs might be whatever risks are incurred by trying to take possession of the benefit, like the potential negative cost of losing a fight. So, sometimes, strategies like sharing benefits with no cost, i.e. risk of injury in this example, can be a good alternative.

We can model the net gain of an individual after an interaction, using the hawk-dove game, in which hawks are always willing to fight for resources, and doves are always peaceful. In an interaction between two doves, each individual will receive equal benefit without any aggression costs. Using this equation, we can calculate the net gain for each individual, which is the benefit minus the cost. That's half B, in this case. In an interaction between a dove and a hawk, the hawk will receive all the benefit, but neither bird will incur immediate costs, because the doves don't engage in conflict. If two hawks interact, they will fight and split the benefit, but also incur some costs, which end up reducing their net gain.

So how do populations strike a balance? In a predominantly sharing group, uncooperative cheaters can out-compete other residents, like this guy, sleeping on his watch. Because of this, many cooperative populations have developed ways to prevent invasion, such as the ability to switch strategies, or identify and punish cheaters with actions like expulsion from the group.

In this lab, you will perform the hawk-dove game, and demonstrate the persistence of two different strategies in a population, and the circumstances that may affect their use.

Print Procedure Steps

The Hawk-Dove Game
- NOTE: In this activity, you will play the hawk and dove game with a single partner and then with multiple partners to observe hypothetical costs and benefits of the antagonist or cooperative behavior respectively.
- Before the activity starts, review the cost-benefit table so that you understand how to score the game. Click Here to download Table 1
- HYPOTHESES: The experimental hypothesis for this exercise could be that the dove strategy will become more frequent between repeated partners, and the hawk strategy will become more frequent when interactions are with a variety of partners. The null hypothesis could be that there will be no change in strategy over time with repeat or different partner combinations. NOTE: Benefit can be determined by looking at the left column and choosing the row that corresponds to the card you played. The box that corresponds to the choice of your partner can be found in the top row. For the purposes of this game, B equals four and C equals three. So depending on the cards played, player one here, which is you, would gain a score of two, four, zero or one half.
- Collect a set of two game cards.
- Take out the cards labeled hawk and dove and place them face down on the table or conceal them in your hands.
- When the instructor gives the signal show either of the two cards to the student sitting across from you. Try to strategize how to receive the highest benefit from every interaction on your own but do not communicate with your partner.
- In the Single Partner Recording Table (Table 2) provided by your instructor, note the cards played as well as the benefit you received for that round.
- Repeat showing cards to the same partner and determining benefit on your instructor's signal for a total of 15 rounds.
- At the end of those rounds, the student with the highest total benefit value was determined to be the “winner”, or the most fit.
- As a class, determine the percentages of hawks and doves played as well as the average benefit received for each round, using this formula: Class average benefit=(sum total benefit)/(number of players)
- For the second game, and then for each round of play, one row of students should rotate to their right, leaving all players with a new partner.
- Continue playing for 15 rounds or until students end up back in their starting positions, recording the data in the Multiple Partner Recording Table (Table 3) given to you by your instructor.
- For each round, determine the percentages of hawks and doves played that round, as well as the average benefit received.
Cheating and Cooperation Exercise
- NOTE: In this activity, you will exchange benefits, represented by colored or similar items, with your classmates. In this simulation, a cheater is defined as a person who gives fewer benefits than they receive. During this activity, you will observe the frequency of cheating behavior over time.
- HYPOTHESES: The experimental hypothesis is that cheaters will receive fewer benefits over time and cooperators will continue to provide equal benefits to one another. The null hypothesis is that the frequency of cheaters and cooperators does not change over time.
- Each person should collect beads of one color to represent a tangible benefit, as well as one paper bag and a three-ring binder.
- Get into a group of three so that all members have objects of the same color.
- Now find another group with a different color to pair with. In each round, partners will exchange benefits without knowing what they are receiving from their partner and without discussion within their group. NOTE: Benefits of a different color from your starting color are worth twice as much.
- Turn face to face with a member from the other group while still being able to conceal the objects in your possession. TIP: Setting up a screen using a notebook or sitting behind a desk can be helpful here.
- When given a signal from the instructor, place zero to two benefits into the paper bag and pass it to your partner.
- Simultaneously, receive the bag from your partner and then remove the benefits from the bag.
- Make a note of how many benefits you gave away and how many you received in the Cheating and Cooperation Table (Table 4) provided by your instructor.
- Turn to a new member from the other group and repeat the exchange.
- Rotate through all of the members of the other group for as many rounds as the instructor determines - which will not be revealed until the game ends so as not to alter player behavior.
- Once the game has ended, note for each round in the cheating and cooperation table whether you gave more than your partner, received more from them or if you gave the same amount.
- Now total up all of the benefits in your possession, with benefits you've received from the other group being worth twice as much.
- For each round, the whole class should total up the number of cheaters - with cheaters defined as those who gave less than they received.
Results
- For both the single partner hawk-dove game and the multiple partners hawk-dove game, use the whole class data to plot the percentages as two separate lines - one for the percentage of hawks, and one for the percentage of doves, for each of the 15 rounds.
- Take note of whether the cards played changed as more rounds were played.
- Manipulate the values for B and C to see if you can find the point at which values of B and C would render the hawk strategy no longer effective (this would be the point when there is no benefit to choosing the hawk strategy over always choosing the dove strategy).
- As a class, use the data from the cheating and cooperation activity to make a graph showing the percentage of rounds each individual player cheated versus the amount of benefits they ended with.
- Consider whether it is better to be a cheater or a cooperator in this scenario and discuss as a class what makes this scenario different from the hawk-dove game.
- Now, use the class data to graph the percentage of cheaters against the number of rounds, and look for any trends over time.
- Consider which type of strategy would most likely evolve in a setting where partners interact repeatedly.
- Then, note which tactic might be beneficial for a species that relies on cooperation.
- Discuss as a class what would likely happen if you increased or decreased the relative value of the benefits you receive.