Main verb

[pankajjindal]

Hi,
I want to understand why "declaring" cannot be the main verb , Is it only due to tense or since it behaves like a adjective ?

In a review of 2,000 studies of human behavior that date back to the 1940s，two Swiss psychologists, declaring that since most of the studies had failed to control for such variables as social class and family size, none could be taken seriously.

[hemant_rajput]

Hi,
I want to understand why "declaring" cannot be the main verb , Is it only due to tense or since it behaves like a adjective ?

In a review of 2,000 studies of human behavior that date back to the 1940s，two Swiss psychologists, declaring that since most of the studies had failed to control for such variables as social class and family size, none could be taken seriously.

declaring is acting as noun. Remember one thing, a gerund (-ing form) is never a verb without a helping verb.