# Evaluating Levels of Automation in Human-Robot Collaboration at Different Workload Levels
## 2 Materials and Methods
### Design of the Experimental Conditions
#### 2.2.2 Levels of Workload  
The workload design focuses mainly on the physical and cognitive workload induced through the selection of the right cubes to assemble in the minimum possible time. This is the main task. Workload is increased in two ways: through a secondary task and by increasing task complexity.  
The secondary task influence was depicted through an off-the shelf well known cognitive game, the \"RUSH HOUR\" ([[https://www.thinkfun.com/products/rush-hour/](https://www.thinkfun.com/products/rush-hour/)]([https://www.thinkfun.com/products/rush-hour/](https://www.thinkfun.com/products/rush-hour/)), accessed on 30 May 2021) thinking game (Figure 3). It involves arranging toy cars in a way to get a specific car out of a gridlock. There are tabs at each stage showing how to arrange the cars and finding a way to get the required red car out at different stages.  
Figure 2: The GUI screen.  
In the main task, where cubes are assembled, the default setting is that the cubes for the assembly differ only by color. The users are required to assemble the cubes to match particular configurations characterized by differences in color pattern (Figure 4a).  
The task complexity influence was depicted by introducing the cubes for the assembly that differ in color and in numbers on a particular side (Figure 4b). The users are required to assemble the cubes in color patterns as done in the low task complexity condition, but in addition, they must ensure that the specific numbers on a particular color of cubes match the required configuration per time. The task complexity is increased by the additional information cue (presence of numbers) and their spatial consideration (position of the number in the configuration). It represents component and coordinative task complexity induced through the number and type of sub-actions to be performed while selecting the right cubes and assembling along with the coordination of the actions in the secondary task. Four levels of workload were designed using these factors:  
1. Low workload (LWL)--the users perform only the main task, assembling cubes (without reference to the numbers on the cubes) to match the specific configuration required. The workload involves some physical demand of arranging the cubes, mental demand of thinking about the type of cube that would match the required configuration and some temporal demand related to completing the task in the shortest possible time.
2. Medium workload 1 (MWL1)--the users perform only the main task of assembling the cubes but with reference to the numbers on the cubes. It depicts the LWL level with increased task complexity (or high workload without secondary task).
3. Medium workload 2 (MWL2)--the users perform the main task of assembling (without references to the numbers on the cubes) simultaneously with the secondary task. It depicts the high workload level without complexity included (or the LWL with a secondary task).
4. High workload (HWL)--the users perform the main task of assembling the cubes (with reference to the numbers on the cubes) along with a secondary task. This combines both secondary task and increased task complexity.  
Figure 4: Sample of cubes configurations in (**a**) without complexity and (**b**) with complexity.  
Figure 3: “RUSH HOUR” game.