Complex sentence: In the mid 90's, prominent linguists including Heidi Harley, Samuel Jay Keyser, and Kenneth Hale proposed that the predicates CAUSE and BECOME, which they referred to as subunits within a Verb Phrase, acted as a lexical semantic template.
Split into simpler sentences: In the mid 90's, prominent linguists including Heidi Harley, Samuel Jay Keyser, and Kenneth Hale turned their attention to the predicates CAUSE and BECOME. They referred to these predicates as subunits within a Verb Phrase structure that acted as a lexical semantic template.