WATCH: Psychologist explains why Trump lies so much -- and why it's getting out of control

Attempting to make sense of President Donald Trump's flurry of lies this week -- particularly with regard to what he has called "Spygate" -- MSNBC host Craig Melvin invited a research psychologist to explain the president's descent into lying almost all of the time.

Melvin kicked off the topic by noting, "A recent CBS poll shows 53 percent, a majority of Americans, believe the Russia investigation is politically motivated; that's up from 48 percent in December. Why? It could very well come down to one thing: President Trump's lies - the sheer number and frequency of them. Researchers have taken a look in the Washington Post's fact checker on President Trump and found the president is now lying more often. He averaged 4.9 falsehoods per day in his first days in the oval office and now 9 lies per day."

The MSNBC host then turned to Tali Sharot, an associate professor of cognitive neurosciences at University College London, and posed the question: "Why an uptick in the president's lies?"

"We don't know specifically about why there's an escalation in the president's lies," Sharot began. "It could be many reasons -- maybe certain lies covered up with more and more lies, maybe falsehoods repeated so many times they are considered to be true, which makes them repeated more."

"Our research suggests that there might be another explanation -- an explanation which is quite intriguing," she continued. "Research done in our lab, not on the president, suggests that the emotional response that people have to their own lies is reduced every time they lie. Now they don't have that negative arousal that comes with lying so there is nothing carving their dishonesty, and so dishonesty just escalates over time."

Describing clinical trials she conducted, Sharot used an analogy to describe Trump's explosion of lying.

"I think the way to think about it is, it's a bit like perfume," she elaborated. "You buy a new perfume, you put it on and it smells quite strongly. Over time you put it again and again and after a while you can't smell it anymore because you have adapted -- you really need to apply it more liberally in order to smell."

"So your own dishonesty, repeated dishonesty, is a bit like perfume that you just adjust to over time and you can't adjust to it anymore," she concluded.

Watch the video below via MSNBC: