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Research Poster PresentationsP O S T E R 2 5The Effects of Signaled Delay andIntertrial Interval Duration onDiscrimination Learning in PigeonsAlexa J. Cimbal, Julyse A.Migan-Gandonou CuFaculty Mentor: Dr. Bertram PloogDepartment of PsychologySixteen pigeons learned a series of reversals of asimultaneous red-green visual discrimination with areinforcement delay of 6 s. The signal presentedduring the reinforcement delay and the intertrialinterval (ITI) was varied between 40-sessionconditions. The main finding was that performancewith the 8-s ITI was higher than with the 40-s ITIand that the introduction of a novel delay signaldisrupted performance, at least temporarily. Thefinding of an ITI effect suggests that performancedepends critically on remembering the outcome ofthe immediately preceding trial. The novel signaleffect suggests that performance depends, at leastin part, on the delay signal’s acquisition ofconditioned reinforcement properties. The study isstill in progress. Future conditions will beconducted in order to (a) replicate the ITI effectand (b) to further understand the role of thedelay signal.P O S T E R 2 6Extending The Census of SimplestHyperbolic KnotsTimothy MullenFaculty Mentor: Dr. Abhijit ChampanerkarDepartment of MathematicsThurston's seminal work established theimportance of hyperbolic geometry in the study of3-manifold topology and knot theory. It is aninteresting problem to study the geometricproperties of hyperbolic knots. The minimumnumber of ideal tetrahedra used to triangulate ahyperbolic knot complement gives a naturalmeasure of its geometric complexity.The census of hyperbolic knots using this measureof complexity gives a different view of the space ofall knots than the view using the diagrammaticcomplexity of knots i.e., the crossing number ofknots. For example, many of the geometricallysimple knots have very high crossing numbers.Hyperbolic knots with geometric complexity up to6 tetrahedra were found by Callahan-Dean-Weeksand extended to 7 tetrahedra by Champanerkar-Kofman-Patterson. In this project we extended theexisting census of simplest hyperbolic knots to 8tetrahedra and are working on providing adiagrammatic description of all the knots.39