This document contains the fourth volume of the proceedings of the 30th Conference of the International Group for the Psychology of Mathematics Education. Conference presentations are centered around the theme "Mathematics at the Centre." This volume features 59 research reports by presenters with last names beginning between Kun and Ros: (1) Evaluational Research on a Video-Based In-Service Mathematics Teacher Training Project--Reported Instructional Practice and Judgements on Instructional Quality (Sebastian Kuntze and Kristina Reiss); (2) Constructing a Sinusoidal Periodic Covariation (Chronis Kynigos and Kostas Gavrilis; (3) Modelling Fractions with Area: The Salience of Vertical Partitioning (Andreas O. Kyriakides); (4) Dynamic Visualization and the Case of "Stars in Cage" (Ilana Lavy); (5) Mathematics, Gender, and Large Scale Data: New Directions or More of the Same? (Gilah C. Leder, Helen J. Forgasz, and Peter J. Taylor); (6) Evaluation and Reconstruction of Mathematics Textbooks by Prospective Teachers (Kyung Hwa Lee); (7) Maths, ICT and Pedagogy: An Examination of Equitable Practice in Diverse Contexts (Stephen Lerman and Robyn Zevenbergen); (8) Solving Problems in Different Ways: Teachers' Knowledge Situated in Practice (Anat Levav-Waynberg and Roza Leikin); (9) Persona-Based Journaling: Aligning the Product with the Process (Peter Liljedahl); (10) The Power of Goal Orientation in Predicting Student Mathematics Achievement (Chuan-Ju Lin, Pi-Hsia Hung, and Suwei Lin); (11) Why Do Student Teachers Teach or Not Teach the Professed Values? (Fang-Chi Lin, Chih-Yeuan Wang, Chien Chin, and Gi-Yuan Chang); (12) Investigating Mathematics Learning with the Use of Computer Programmes in Primary Schools (Maria Dolores Lozano, Ivonne Twiggy Sandoval, and Maria Trigueros); (13) Is Subject Matter Knowledge Affected by Experience? The Case of Composition of Functions (Calin A. Lucus); (14) Classroom Factors Supporting Progress in Mathematics (Irene F. Mackay); (15) A Remedial Intervention in Algebra (Laura Maffei and Maria Alessandra Mariotti); (16) The Problem-Solving Element in Young Students' Work Related to the Concept of Area (Joanna Mamona-Downs and Ioannis Papadopoulos); (17) On Students' Conceptions in Vector Space Theory (Mirko Maracci); (18) Towards the Development of a Self-Regulated Mathematical Problem Solving Model (Andri Marcou and Stephen Lerman); (19) Visual Cognition: Content Knowledge and Beliefs of Preschool Teachers (Zvia Markovits, Sherman Rosenfeld, and Bat-Sheva Eylon); (20) An Unexpected Way of Thinking about Linear Function Tables (Mara Martinez and Barbara Brizuela); (21) Levels of Understanding of Patterns in Multiple Representations (Stalo Michael, Iliada Elia, Athanasios Gagatsis, Athina Theoklitou, and Andreas Savva); (22) Can the Spontaneous and Uncritical Application of the Linear Model be Questioned? (Modestina Modestou and Athanasios Gagatsis); (23) Primary Students' Reasoning in Problem Solving and Teachers' Evaluation of Their Arguments (Annita Monoyiou, Xenia Xistouri, and George Philippou); (24) Use of Examples in Conjecturing and Proving: An Exploratory Study (Francesca Morselli); (25) Knowledge Building and Knowledge Forum: Grade 4 Students Collaborate to Solve Linear Generalizing Problems (Joan Moss and Ruth Beatty); (26) Improving Mathematical Knowledge through Modeling in Elementary Schools (Nicholas Mousoulides, Marios Pittalis, and Constantinos Christou); (27) Integrating Concepts and Processes in Early Mathematics: The Australian Pattern and Structure Mathematics Awareness Project (PASMAP) (Joanne Mulligan, Michael Mitchelmore, and Anne Prescott); (28) Embodiment and Reasoning in Children's Invented Calculation Strategies (Carol Murphy); (29) When the Wrong Answer is the "Good" Answer: Problem-Solving as a Means for Identifying Mathematical Promise (Dorit Neria and Miriam Amit); (30) The Concept of Equations: What Have Students Met Before? (Rosana Nogueira de Lima and David Tall); (31)Teaching Becomes You: The Challenges of Placing Identity Formation at the Centre of Mathematics Pre-Service Teacher Education (Kathleen T. Nolan); (32) Structure Sense for University Algebra (Jarmila Novotna, Nad'a Stehlikova and Maureen Hoch); (33) Semiotic Chaining in an Expression Constructing Activity Aimed at the Transition from Arithmetic to Algebra (Masakazu Okazaki); (34) Kikan-Shido: Through the Lens of Guiding Student Activity (Catherine A. O'Keefe, Xu Li Hua, and David J. Clarke); (35) Hiding and Showing Construction Elements in a Dynamic Geometry Software: A Focusing Process (Federica Olivero); (36) Prompting Growth for Prospective Teachers Using Cognitive Dissonance (Jo Clay Olson, Meghan Colasanti, and Karmin Trujillo); (37) Metacognition and Reading--Criteria for Comprehension of Mathematics Texts (Magnus Osterholm); (38) Classification Activities and Definition Construction at the Elementary Level (Cecile Ouvrier-Buffet); (39) Abstraction, Scaffolding and Emergent Goals (Mehmet Fatih Ozmantar and John Monaghan); (40) Cognitive and Metacognitive Performance on Mathematics (Areti Panaoura and Georgia Panaoura); (41) Measuring and Relating Primary Students' Motives, Goals and Performance in Mathematics (Marilena Pantziara and George Philippou); (42) The Intuitive Rule More A-More B: The Impact of a Dynamic Geometry Software (Pandelitsa Papageorgiou, Annita Monoyiou, and Demetra Pitta-Pantazi); (43) The Reflective Abstraction in the Construction of the Concept of the Definite Integral: A Case Study (Theodorus Paschos and Vassiliki Farmaki); (44) Infinity of Numbers: How Students Understand It (Erkki Pehkonen, Markku S. Hannula, Hanna Maijala, and Riitta Soro); (45) The Assessment of Undergraduate Mathematicians: Recrafting Assessment of Learning to Provide Opportunities for Assessment as Learning (Hillary Povey and Corinne Angier); (46) Social Cognition Emerging from Student-to-Student Discursive Interactions during Mathematical Problem Solving (Arthur B. Powell); (47) Understanding Teachers' Mathematical Knowledge for Teaching: A Theoretical and Methodological Approach (Arthur B. Powell and Evelyn Hanna); (48) Continuities and Discontinuities for Fractions: A Proposal for Analysing in Different Levels (Susanne Prediger); (49) Dynamic Manipulation Schemes of Geometrical Constructions: Instrumental Genesis as an Abstraction Process (Giorgos Psycharis); (50) Rhythm and the Grasping of the General (Luis Radford, Caroline Bardini, and Cristina Sabena); (51) Developing Mathematical Initiative in Minority Students (Iuliana Radu, Barbara Tozzi, and Keith Weber); (52) A Model of Textbook Use (Sebastian Rezat); (53) Identical Twins' Perceptions of Two Different Instructional Approaches to Learning Mathematics (Candice L. Ridlon); (54) When Successful Comparison of Decimals Doesn't Tell the Full Story (Anne Roche and Doug M. Clarke); (55) Analysis of Proofs Produced by University Mathematics Students, and the Influence of Using Cabri Software (Felix Rodriguez and Angel Gutierrez); (56) Challenging the Mathematical Beliefs of Preservice Elementary School Teachers (Katrin Rolka, Bettina Rosken, and Peter Liljedahl); (57) Partial Knowledge Constructs for the Probability Area Model (Gila Ron, Tommy Dreyfus, and Rina Hershkowitz); (58) A Picture is Worth a Thousand Words--The Role of Visualization in Mathematics Learning (Bettina Rosken and Katrin Rolka); and (59) Establishing and Justifying Algebraic Generalization at the Sixth Grade Level (Joanne Rossi Becker and Ferdinand Rivera). (Individual papers contain references.)