TABLE OF CONTENTS § i- § 2. § 3- § 4- § 5- § 6. § 7- § ». § 9- § io. § h. § 12. § 13- § 14- INTRODUCTION MENTAL MEASUREMENT Measurement........ Mental Measurement...... An Analogy ........ Three Problems of Quantitative Psychology . Some Technical Terms...... The Further Programme of Quantitative Psychology Questions ... . . . . . PAGE xix xxi xxvii xxix xxxvii xxxviii xl CHAPTER I. PRELIMINARY EXPERIMENTS Experiment I The Qualitative RL for Tones : the Lowest Audible Tone . I Experiment II The Qualitative RL for Tones : Alternative Experiment . io Experiment 111 The Qualitative TR for Tones: the Highest Audible Tone . 12 Experiments IV-VI The Intensive RL for Pressure......14 Experiments VII, VIII The Intensive RL for Sound.......22 Weber’s Law..........25 Experiments IX-XII Demonstrations of Weber’s Law: Fechner’s Cloud Experi¬ ment; Fechner’s Shadow Experiment; Sanford’s Weight Experiment; Ebbinghaus’ Brightness Experiment . . 29 xi