This is bad, because the information about the correct attachment could come from the lexical content of node P. The arc-eager model performs slightly better, since it can delay the decision up to the point in which α 1 has been constructed and P is read from the buffer.
at this point it must make a commitment and either construct α 3 or pop N1 from the stack (implicitly committing to α 2 ) before N2 is read from the buffer.