Human brain can quickly understand words for big things, like whale, than 'small' words like plum, a new study has found.

Researchers at the University of Glasgow had previously found that big concrete words - ocean, dinosaur, cathedral were read more quickly than small ones such as apple, parasite and cigarette.

Now they have discovered that abstract words which are thought of as big ? greed, genius, paradise are also processed faster than concepts considered to be small such as haste, polite and intimate.

"It seems that size matters, even when it's abstract and you can't see it," Dr Sara Sereno, a Reader in the Institute of Neuroscience and Psychology, who led the study said.

Participants were presented with a series of real words referring to objects and concepts both big and small, as well as nonsense, made-up words, totalling nearly 500 items. The different word types were matched for length and frequency of use.

The 60 participants were asked to press one of two buttons to indicate whether each item was a real word or not. This decision took just over 500 milliseconds or around a half second per item.

Results showed that words referring to larger objects or concepts were processed around 20 milliseconds faster than words referring to smaller objects or concepts.

"This might seem like a very short period of time, but it's significant and the effect size is typical for this task," said Sereno.

"It turned out that our big concrete and abstract words, like 'shark' and 'panic', tended to be more emotionally arousing than our small concrete and abstract words, like 'acorn' and 'tight'. Our analysis showed that these emotional links played a greater role in the identification of abstract compared to concrete words," Lead author Dr Bo Yao said.

"Even though abstract words don't refer to physical objects in the real world, we found that it's actually quite easy to think of certain concepts in terms of their size," said co-author Professor Paddy O'Donnell.

"Everyone thinks that 'devotion' is something big and that 'mischief' is something small," O'Donnell said.

Bigger things it seems, whether real or imagined, grab our attention more easily and our brains process them faster even when they are represented by written words.

The study was published in the journal PLoS ONE.