I’ve been collecting quite a bit of data with my game lately, and a colleague (Samuel P. Leon) will be presenting some of the data at the Spanish Society for Comparative Psychology’s annual meeting in Salamanca this year. Rather than try to describe the method, I made a somewhat explanatory video for him to use in the meeting, which is presented a bit further down in this blog post. I thought it was time that I presented a more precise description of the game.
The game was designed to study associative learning in humans using a behavioral, as opposed to self-report, task. That is, we infer what it is that people have learned based on what they do (rather than what they might tell you).
Any experiment is divided into at least two phases, based loosely on the ideas of Ivanov-Smolensky. First, particular responses are attached to particular stimuli (the conceptual “Unconditioned Stimulus” or USs). Then, those USs are are predicted by other stimuli, the Conditioned Stimuli (CSs). As an association is formed between the CS and the US, the response we attached to the US comes to be elicited by the CS.
In the game, this means that a sensor (CS) predicts a ship (US) and the player tells us that he or she knows this by charging a weapon that is used to repel the ship when the sensor is lit. Thus, there must be minimally two phases. First, the player learns how to respond when a ship is present, and then the second phase is experiment specific, depending on what it is the researcher wishes to study about the learning process. I’ll describe simple conditioning in phase II below.
The first phase is designed to attach a particular response to a stimulus. The phase begins with a backstory. The participant is told that they have been recruited by the aged “protector of the galaxies” to use the “battlesphere” to protect the stations of the galaxies from possible invasions. To do so, they must learn to use the weapons of the battlesphere as each weapon was designed to repel a particular invader. In the game, four different spaceships serve as USs.
On the very first trial with a particular spaceship, the spaceship will appear along with a message (both in text and over the headphones) that states something along the lines of “The ship that just appeared is the (name of ship). Take a few moments to study and remember its appearance. It is being tracked by the (name of weapon) in the (corner of screen). Use the (name of key) to prepare the weapon so that it fires sooner and more rapidly than it would on its own. Rapidly press the (name of key) until the weapon begins to fire and the (name of ship) is repelled.” The participant then begins pressing the key and the weapon charges and begins firing. After a few shots (experimenter defined) the ship will rapidly fly out of the area.
When the spaceship leaves, another message appears that congratulates the player and tells them to remember that they must use the (name of key) to prepare the (name of weapon) to repel the (name of ship) and to practice for a few trials.
Each trial from that point on involves the appearance of the spaceship which remains until the participant prepares the weapon and drives the ship away, followed by an inter-trial interval of about 5-s. The messages that appeared on the first trial no longer appear.
It doesn’t take people long to master this simple task. After three or four appearances of the spaceship, participants will immediately begin to rapidly (~ 5 presses per second) hit the appropriate key. I typically use about six to eight of these practice trials, per ship.
At the end of all the trials, a message appears informing the player that they are now ready for their patrols and that they will be transported to their first patrol. They are told by the aged protector that there is much of the technology that has been forgotten that they must learn on their own. A “wormhole” is opened and the player is transported to their first patrol.
The experimenter can program four different ships during this phase. The first appearance of any particular spaceship is accompanied by the instructions above (On the very first trial..). All the instructions are modifiable by the researcher via a text file, as are the timing parameters, as well as whether the ships remain on the screen until they are shot at a set number of times, or a particular amount of time elapses. More than one ship can appear at the same time. Thus, a player might have to learn to press the backspace key to repel one ship and the left-shift key to repel another at the same time. There is a great deal of flexibility for the researcher.
The four ships are shown below. The blue saucer ship is the Learian.
The Juk destroyer.
The Learian is repelled by the “SOP Cannon” (Backspace key)
The Luckonian is repelled by the “IBO laser” (left-shift)
Each weapon was designed to bear some resemblance to the ship it is used against, and its location in the screen bears some correlation to the placement of its use key on the keyboard.
In phase two, the participant is transported to a galaxy to patrol & protect the galaxy’s station. There are four different galaxies that might be used, pictured below.
Phase II is very simple. In this phase, trials are generally 20-s long. A trial begins with the presentation of a CS. CSs are presented in the form of an illuminated sensor on the panel in the middle. These are illuminated for some seconds (I typically use 5) before a ship appears. The ship appears and begins attacking the station and the sensor remains illuminated. After 15 seconds, the ship leaves regardless of what the player does and the sensor goes off.
The first phase has trained the player to press a particular key when a ship appears, thus when the ship appears they begin pressing the key, charging the weapon, which then begins firing and they continue firing until the trial is over. Should a player not charge the weapon, the ship attacks the station for 15 seconds and then the players weapon fires once on its own and the ship leaves.
After a few trials, players begin charging the weapon as soon as the CS appears so that the weapon begins firing the moment the ship appears. In this case, the ship raises its shield and cannot attack the station. It is that anticipatory responding to the CS that is taken as evidence of associating the sensor CS with the ship US.
Any number of phases and trials can be created to study conditioning, extinction, context-specific learning, conditioned inhibition… basically any associative-learning process can be investigated with the method.