?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=Ultrametric+Distance+in+Syntax&rft.creator=Roberts%2C+Mark+D.&rft.subject=Cognitive+Psychology&rft.subject=Speech&rft.subject=Syntax&rft.description=Phrase+structure+trees+have+a+hierarchical+structure.+In+many+subjects%2C+most+notably+in+Taxonomy+such+tree+structures+have+been+studied+using+ultrametrics.+Here+syntactical+hierarchical+phrase+trees+are+subject+to+a+similar+analysis%2C+which+is+much+simpler+as+the+branching+structure+is+more+readily+discernible+and+switched.+The+occurrence+of+hierarchical+structure+elsewhere+in+linguistics+is+mentioned.+The+phrase+tree+can+be+represented+by+a+matrix+and+the+elements+of+the+matrix+can+be+represented+by+triangles.+The+height+at+which+branching+occurs+is+not+prescribed+in+previous+syntactic+models%2C+but+it+is+by+using+the+ultrametric+matrix.+In+other+words+the+ultrametric+approach+gives+a+complete+description+of+phrase+trees%2C+unlike+previous+approaches.+The+ambiguity+of+which+branching+height+to+choose%2C+is+resolved+by+postulating+that+branching+occurs+at+the+lowest+height+available.+An+ultrametric+produces+a+measure+of+the+complexity+of+sentences%3A+presumably+the+complexity+of+sentences+increases+as+a+language+is+acquired+so+that+this+can+be+tested.+All+ultrametric+triangles+are+equilateral+or+isoceles%2C+here+it+is+shown+that+%5C%3D%7BX%7D+structure+implies+that+there+are+no+equilateral+triangles.+Restricting+attention+to+simple+syntax+a+minimum+ultrametric+distance+between+lexical+categories+is+calculated.+This+ultrametric+distance+is+shown+to+be+different+than+the+matrix+obtained+from+features.+It+is+shown+that+the+definition+of+%7B%5Csc+c-command%7D+can+be+replaced+by+an+equivalent+ultrametric+definition.+The+new+definition+invokes+a+minimum+distance+between+nodes+and+this+is+more+aesthetically+satisfying+than+previous+varieties+of+definitions.+From+the+new+definition+of+%7B%5Csc+c-command%7D+follows+a+new+definition+of+%7B%5Csc+government%7D.&rft.date=1995&rft.type=Preprint&rft.type=NonPeerReviewed&rft.format=application%2Fpostscript&rft.identifier=http%3A%2F%2Fcogprints.org%2F225%2F2%2Fudv3.ps&rft.identifier=++Roberts%2C+Mark+D.++(1995)+Ultrametric+Distance+in+Syntax.++%5BPreprint%5D++++(Unpublished)++&rft.relation=http%3A%2F%2Fcogprints.org%2F225%2F