Principles and Pop Culture – Super Mario Bros.? and Discriminated Behavior
Behavior analysis is the scientific study of the interaction between behavior and environmental events (Skinner, 1953). Born out of scientific investigation is both the uncovering of the basic principles underlying behavior and environmental interactions as well as practices that rely on this knowledge to change behavior to meet the contingencies of the environment. Thus, basic science informs practical application. Therefore, it is important for practitioners of behavior analysis to be highly fluent in the description, observation, and programming of basic behavioral principles when seeking to change behavior. In this article, we will review the basic principle of stimulus discrimination, which describes the relationships between stimuli and how they can affect behavior. In doing so, a hopefully reinforcing exemplar has been selected in order to provide a different description of this topic.
Super Mario Bros.? is a video game created by Nintendo Co., Ltd. originally released in the United States in 1985 (Nintendo, 2020). It is a game that allows players to move an onscreen character (Mario) across a scrolling left to right screen in which numerous obstacles are encountered (Super Mario Bros., 1985). To play the game, players move Mario by pressing left or right on a directional pad. In addition, pressing the A button on the controller makes Mario jump and pressing the B button allows Mario to run faster or to shoot fireballs, when this ability is available. The primary goal is to make it from the beginning to the end of each level without Mario touching specific onscreen objects or falling into specific areas.
The game provides many examples of stimuli in which success within the game relies on discriminated behavior. In order to review this concept, let’s discuss the first level of the game: World 1-1. As Mario begins moving forward, the player encounters two differing stimuli. The first is an orange box with a question mark inside of it, slightly above Mario’s head. The second stimulus is a moving mushroom shaped character named Goomba. These two stimuli present the first opportunity to discriminate the player’s behavior. If the player moves Mario underneath the question box, or block as it is referred to, and presses the A button, Mario jumps up and hits the block with his head. This results in a high-pitch musical note along with a coin that pops up out of the block. The coin that is gathered then results in a subsequent increase in an onscreen counter measuring the number of collected coins. Assuming most individuals playing this game have a conditioning history with either whimsical musical sounds and/or coins, these are likely to serve as conditioned reinforcers. Thus, the behavior of moving the character underneath a block and pressing the A button achieves potential reinforcement. We will return to verify that point, but Mario must first encounter the next stimulus, the Goomba. If the player moves Mario forward and comes into contact with the Goomba, the character shoots up into the air and then falls off of the screen. This sequence of events is then accompanied by a series of lower musical notes that play until the turn is ended. Touching Goomba from the side results in the termination of the player’s ability to continue playing the game for at least a few seconds. Within these two stimuli (i.e., the question mark box and the Goomba), the game illustrates the three relations of discriminated behavior (i.e., SD’s, S-delta’s, and SDP’s).
A discriminative stimulus (SD) is defined as an environmental event which signals the availability of reinforcement for a specific behavior (Michael, 1980). In other words, a stimulus becomes a SD when a behavior is regularly reinforced when in the presence of that stimulus. Throughout the rest of the level, a block signals to the player to place Mario below and press the A button to hit the block. Reinforcers such as the coin and sound mentioned previously are delivered, which begins to condition these blocks as a discriminative stimulus. The next block that Mario encounters provides a different reinforcer. A mushroom appears that, if touched by the character, increases the size of Mario on the screen. Additional blocks throughout the level provide either coins, a growth mushroom, an extra life mushroom, a flower that allows Mario to shoot fireballs, or a star that makes Mario immune to harm from Goombas or other enemies. If the player regularly hits blocks within the levels, then the items gained and/or the sounds played are serving as conditioned reinforcers. As a result, the block has become a SD.
A discriminative stimulus of extinction (S-delta) can be defined as an environmental event that signals that reinforcement is not available if a specific behavior is engaged in (Pierce & Cheney, 2017, p. 255). In the past, the behavior has not received reinforcement when conducted in the presence of this stimulus. In relation to the block, there are several behaviors that will not achieve gaining access to the above described items or sounds. If Mario is made to jump on top of the block instead of underneath it or if the player has Mario simply run under the block, the previously stated reinforcers will not be delivered. Therefore, given no additional stimuli, the block serves as an S-delta for running underneath without jumping or jumping on top of, since these behaviors will not achieve the reinforcers that hitting the block will. However, behavior and environmental interactions are not always this simplistic; therefore, if a Goomba is walking towards Mario and the player jumps on top of a block to avoid it, this could reinforce jumping on the block when a Goomba is present, making the block with a Goomba present an SD for jumping on top. Although, in most scenarios in this level, the block serves as an S-delta for jumping on top or just running underneath.
There is one additional example of how SD’s and S-deltas can serve to discriminate behavior. When Mario first approaches a block, it is orange in color and has the question mark in the middle of it. If Mario goes underneath and jumps to hit the block, a reinforcer appears as described above. Thus, the block serves as an SD for this behavior. However, after Mario hits the block and the item (coins, mushroom, etc.) is delivered, the block turns the color brown. After the color change, hitting the block no longer results in the musical note or obtaining additional items. This teaches the player to discontinue pressing the A button to have Mario jump to hit brown blocks. The brown colored block can then be described as S-delta, as it signals that extinction or the lack of reinforcement for a behavior that was previously being reinforced is in place. Therefore, players learn to jump under orange blocks with question marks and to not jump under brown blocks. This illustrates the relationship of behavior conditioned to be discriminated across differing stimuli.
A discriminative stimulus of punishment (SDP) is defined as an environmental event that signals that a behavior will be punished if it occurs (O’Donnel, 2001). This relationship develops when a behavior is consistently punished (i.e., receives aversive consequences) when it occurs after a specific stimulus. In the game, touching a Goomba results in the player’s ability to continue the game to be suspended for a period of time. If the player begins to avoid touching the Goomba after receiving this consequence, then the behavior of touching the Goomba has been punished. The Goomba then serves as a SDP for the behavior of moving Mario to touch the Goomba. Again, there are more environmental variables to unpack here. If the player begins to vary their behavior and by chance jumps on top of the Goomba, they experience that the enemy flattens on screen and disappears, without causing the game to be stopped. If the behavior of pressing the A button to jump on the Goomba increases when playing the game, then the Goomba serves as a SD for pressing the A button to jump on the Goomba while also serving as a SDP for running into the side of the Goomba. Thus, this stimulus (the Goomba) causes discriminated behavior by signaling that one behavior (jumping on top of the Goomba) will receive reinforcement and a different behavior (running into the side of the Goomba) will receive punishment.
Discrimination of stimulus/behavior relations is a basic principle of behavior analysis that accounts for an extremely broad range of behavior. Hopefully this comical review of environmental and behavior interactions further clarifies these relations. In an interview, the creator of Super Mario Bros.?, Shigeru Miyamoto explained that World 1-1 was designed to train the player on how to behave within the game (Robinson, 2015). Using the principles of discriminated behavior, it is easy to see how this aim was accomplished.
References
Nintendo. (2020, Jan. 8). History. Retrieved from https://mario.nintendo.com/history/
Michael, J. (1980). The discriminative stimulus or SD. The Behavior Analyst, 3, 47-49.
O’Donnel, J. (2001). The discriminative stimulus for punishment or SDp. The Behavior Analyst, 24, 261-262.
Pierce, W. D. & Cheney, C. D. (2017). Behavior analysis and learning: A biobehavioral approach (6th ed.). New York, NY: Routledge.
Skinner, B. F. (1953). Science and human behavior. New York, NY: The Free Press.
Super Mario Bros. [Video game]. (1985). New York, NY: Nintendo.