Present perfect In british and american

The aim of the research work is to analyze the reasons of the frequency of the use of Present Perfect and Past Simple verb forms on the example of American and British fiction and to identify this frequency.
Objectives are:
- to study the definition and characteristics of the category of tense of English verbs;
- to examine the peculiarities of Present Perfect and Past Simple;
- to compare the frequency of the use of Present Perfect Tense and the Past Simple Tense in American and British English and to identify the average ratio of Present Perfect to Past Indefinite.