ACT-R is a cognitive architecture. In essence, it's a theory about how the human cognition works. Having a theory about how our cognition works enables us to figure out the steps which happen when we are perceiving certain data and afterwards changing the world  given that data. This is ACT-R's architecture of the human cognition:  ![[act-r.png]] As we can see in the image, ACT-R interacts with the world in a two-way manner (input and output) and does central processing too. Again, this is an architecture that tries to represent how the human cognition works; not just any cognition. That is why each of the parts of the architecture is experimentally bounded to actual areas of the human brain. Talking specifically about the diagram, we can see that there are eight boxes. These boxes are called **modules**. Each module is capable of performing **specific kind of functions**. For example: the **vision module** is specialized in finding and attending visual objects and the **declarative** **module** is specialized in holding memories. The orchestra of modules is ordered by a central module called the **procedural module**. This module is the only one that is connected to all the modules and its responsible of giving instructions to the modules. After an instruction is received, a module can work independently, but the initial instruction has to be given by the procedural module.  In a way, the procedural module is the one that makes **decisions**. As I said before, having an architecture like this enables us to figure out the steps which happen when we are perceiving certain data and changing the world  given that data. For an example, imagine the next experiment: 1. Two **numbers** are shown on the screen, one on each side of the screen (left and right) 2. The agent has to choose which one is larger 3. The agent has to press a key indicating which one is larger 1. If the one on left is larger, press the "←" key 2. If the one on right is larger, press the "→" key 3. If they are equal, press the "↓" In this simple example, the ACT-R architecture can help us prepare the next initial model of the situation: 1. The **vision module** sees two objects on the screen 2. The **vision module** attends the object on the left first. It then saves the perceived content on the imaginal module (short-term memory). 3. The **vision module** attends the object on the right. It then saves the content on the imaginal module (short-term memory). 4. Using data on the **declarative module** (memory), the **symbols** (numbers) are transformed into **numerical values.** 5. The values are compared and, on the **procedural module**, a decision is taken over which button to press. 6. The **motor module** performs the action of pressing the specified button. This step-by-step analysis of the experiment is clearly very simple. Nonetheless, its simplicity opens the path to make a simulation of the situation. The results of this simulations, if correct, should match the results of an experiment with real human-beings. If this was the case, the simulation would be a success. Official website: http://act-r.psy.cmu.edu/