אַמַּאי? לֵימָא: כׇּל שֶׁאֵינוֹ בְּזֶה אַחַר זֶה — אֲפִילּוּ בְּבַת אַחַת אֵינוֹ!

According to Rabba’s opinion, the question arises: Why should the produce be rendered fit for consumption? Let us say and apply his principle: Anything that cannot be accomplished sequentially; even simultaneously it cannot be accomplished. Since one may not designate two tenths sequentially, one tenth followed by a second tenth, likewise, he should be precluded from simultaneously designating two tenths of his produce as a tithe. Accordingly, it should be considered as though he had not designated any tithe at all, and therefore his produce should not be regarded as tithed.

Let us mediate on the concept of multi-tasking. 

Can One Think two thoughts at the same time? Conventional wisdom says no. However, a recent study using functional MRI’s shows that each of the two brain hemispheres can divide into two once again, and manage albeit less efficiently two tasks at the same time. On the other hand, three tasks is overload. Let us try to understand why:

The prefrontal cortex has an anterior and a posterior region. It also is divided into right and left hemispheres. The anterior region is in charge of setting the goal, the posterior region is in charge of managing the task. When study participants were asked to select letters from a random pile that match up to a given word, the functional MRI was able to track the typical anterior-posterior chain of events. However, if they were also asked to divide them up between upper and lower case, then the activity divided into four regions: anterior-posterior, right and left. Since the brain has two hemispheres, it can manage to do the two tasks. However when a third variable was added into the task, participants would get confused and inevitably forget one of the three. This shows that the brain anatomy corresponds convincingly to the ability. Two tasks are okay, three is overload.

Here is a link and citation to the study: 

https://science.sciencemag.org/content/328/5976/360.abstract

Divided Representation of Concurrent Goals in the Human Frontal LobesBY SYLVAIN CHARRON, ETIENNE KOECHLIN (SCIENCE16 APR 2010 : 360-363) The human brain is limited to accurately negotiate the pursuit of two concurrent goals at the same time.

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Translations Courtesy of Sefaria