Maybe I'm picking a nit here. But even a single core processor can do multi-tasking, that's what a modern OS such as Windows and Linux is doing.
In your case, it could be caused by many factors. One possible reason is that your task switching itself is the bottleneck, say, saving current context into stack and loading previous context from stack. It's very fast in computers just a few memory access and overwriting a few registers, human brain cell is different storage, the process may take much longer. Not sure if it can be trained to be faster though.
Another possible cause (and maybe worse) is that the main memory is very limited, such that only one of tasks can stay in the memory, every time you need to switch to another task, you encounter a page fault that triggers the OS to load the task from the much slower hard drive. I guess maybe it's the case in brain as well, there are areas for storing short-term memory and for long-term memory respectively, while the former has faster access speed but much limited capacity.
In your case, in order to maximize your throughput, you make the multitasking OS running into a batch mode.
In your case, it could be caused by many factors. One possible reason is that your task switching itself is the bottleneck, say, saving current context into stack and loading previous context from stack. It's very fast in computers just a few memory access and overwriting a few registers, human brain cell is different storage, the process may take much longer. Not sure if it can be trained to be faster though.
Another possible cause (and maybe worse) is that the main memory is very limited, such that only one of tasks can stay in the memory, every time you need to switch to another task, you encounter a page fault that triggers the OS to load the task from the much slower hard drive. I guess maybe it's the case in brain as well, there are areas for storing short-term memory and for long-term memory respectively, while the former has faster access speed but much limited capacity.
In your case, in order to maximize your throughput, you make the multitasking OS running into a batch mode.