• Present Perfect
• markedness
• difficulty
• complexity
• resultativeness

The aim of this thesis is to show that the different Present Perfect interpretations make up a system of periphrastic constructions with variable degrees of complexity resulting from the interplay of lexico-syntactic, semantic and pragmatic factors. The meanings associated with Present Perfect constructions range along an explicit-implicit spectrum whose extremes are characterised on the one hand by the expression of objectively verifiable conditions and, on the other, by subjective “representations of evidence”.
The complexity of the Present Perfect system will be evaluated on the basis of the semiotic principles of iconicity/diagrammaticity, indexicality, biuniqueness, transparency and figure/ground (Merlini Barbaresi 1988b, 2003b), particularly with reference to the notion of resultativeness. It will then be demonstrated that the whole apparatus of Present Perfect constructions can be described in terms dynamicity, non-linearity, nestedness, adaptability, self-organisation and stochasticity (Bertuccelli Papi 2003a, Bertuccelli Papi & Lenci 2007), which are indeed the typical features of complex systems.
The present analysis is corpus-based. Data have been extracted from the written component of the British National Corpus and from a number of other corpora of British and non-British English.