[jtoy4eva]

ALkyne are expected to be more reactive than alkene but it is not.

how can we explain in terms of electrophilic additions?

[reflux]

It depends on what type of electrophilic addition but what would the intermediate of your reaction be? 

For example, if you form a carbocation which one is more stable?  The sp2 carbocation generated from the alkene or the sp carbocation (vinyl carbocation) generated from the alkyne?  Are there any other factors like resonance, hyperconjugation, inductive effects, or electronegativity involved?

Those are some of the questions you can use to rationalize the relative reactivites.