Donald Trump speaks like a sixth grader: Study

Republican presidential hopeful Donald Trump may have mesmerised his fans with provocative speeches but researchers have found that in terms of use of words and grammar, he can be compared to a sixth grader.

Most presidential candidates in the US are using words and grammar typical of students in grades six to eight, though Donald Trump tends to lag behind the others, the study said.

For the study, the researchers at Carnegie Mellon University's Language Technologies Institute (LTI) did a readability analysis of presidential candidate speeches.

A historical review of their word and grammar use suggests that all five candidates in the analysis -- Republicans Trump, Ted Cruz and Marco Rubio (who has since suspended his campaign), and Democrats Hillary Clinton and Bernie Sanders -- have been using simpler language as the campaigns have progressed, the researchers said.

Again, Trump is an outlier, with his grammar use spiking in his Iowa Caucus concession speech and his word and grammar use plummeting again during his Nevada Caucus victory speech, according to the study.

A comparison of the candidates with previous presidents showed president Abraham Lincoln outpacing them all, boasting grammar at the 11th grade level, while president George W. Bush's fifth grade grammar was below even that of Trump.

"Assessing the readability of campaign speeches is a little tricky because most measures are geared to the written word, yet text is very different from the spoken word," said one of the researchers Maxine Eskenazi in an official statement.

"When we speak, we usually use less structured language with shorter sentences," Eskenazi noted.

The researchers used a readability model called REAP, which looks at how often words and grammatical constructs are used at each grade level.

Based on vocabulary, campaign trail speeches by past and present presidents -- Lincoln, Reagan, Bill Clinton, George W. Bush and Obama -- were at least on the eighth grade level, while the current candidates ranged from Trump's seventh grade level vocabulary to Sanders' 10th grade level.

In terms of grammar, the current candidates generally had scores between sixth and seventh grades, with Trump just below sixth grade level, the study said.