Introduction to Psychophysics with Python

Cover....1

Half Title....2

Copyright Page....3

Title Page....4

Table of Contents....6

Preface....10

Acknowledgements....12

Aims and Objectives....14

List of Abbreviations....16

About the Authors....18

Chapter 1: History of Psychophysics....20

1.1: Truth and Scientific Method....20

1.2: What is Psychophysics?....20

1.2.1: Psychophysics in the scientific method....21

1.2.2: Relation to psychology....21

1.3: Why Psychophysics?....21

1.4: Timeline of Key Developments....24

1.5: Webers and Fechners Laws....25

1.5.1: Webers law....25

1.5.2: Fechners Law....27

1.6: Experimental Paradigms: A Brightness JND Example....27

1.6.1: Method of limits....27

1.6.2: Method of constant stimuli....28

1.6.3: Method of adjustment....28

1.6.4: Comparing the methods....29

1.7: Preparing PsychoPy....29

1.7.1: Installing PsychoPy via web resources....29

1.8: A Simple PsychoPy Brightness JND Experiment....29

1.8.1: PsychoPy script....30

1.8.2: Analysis in Google Colab: Step by step explanation....32

1.9: Conclusion....34

1.10: Exercises: History of Psychophysics....35

1.11: Further Reading....36

Chapter 2: Understanding Sensory Systems....38

2.1: Introduction....38

2.1.1: Sensory modalities and their functions....38

2.2: Sensation vs. Perception....40

2.2.1: Clinical relevance....41

2.3: Vision....41

2.3.1: Anatomy and optics of the eye....41

2.3.2: Dual visual pathways....44

2.3.3: Visual psychophysics paradigms....46

2.4: Audition....49

2.4.1: Anatomy of the ear....49

2.4.2: Sound localization cues....52

2.4.3: Auditory psychophysics paradigms....53

2.5: Touch (Somatosensation)....55

2.5.1: Anatomy and receptor types....55

2.5.2: Neural pathways....55

2.5.3: Key psychophysical paradigms....56

2.5.4: Examples and applications....56

2.6: Taste (Gustation)....57

2.6.1: Anatomy and receptor mechanisms....57

2.6.2: Neural pathway....57

2.6.3: Key psychophysical paradigms....57

2.6.4: Examples and applications....58

2.7: Smell (olfaction)....58

2.7.1: Anatomy and receptor mechanisms....58

2.7.2: Neural pathways....59

2.7.3: Key psychophysical paradigms....59

2.7.4: Examples and applications....60

2.8: Psychophysics and Developmental Psychology....61

2.8.1: Historical foundations: The work of Robert Fantz....61

2.8.2: Infant looking paradigms in psychophysical research....62

2.8.3: Technological advances in infant looking studies....65

2.9: Example PsychoPy Experiment: A Working Memory Sequence–Judgement Task....65

2.9.1: Experiment code....67

2.9.2: Running the experiment....71

2.9.3: Data analysis in Google Colab....71

2.10: Student Exercises....73

2.11: Additional Reading....74

Chapter 3: Signal Detection Theory and Experimental Design....76

3.1: Introduction to Psychophysical Methods....76

3.1.1: The scientific method in psychophysics....76

3.1.2: Experimental variables....77

3.1.3: Validity and reliability....77

3.1.4: Key concept: Counterbalancing and randomization....77

3.1.5: Applying psychophysical principles to the serial memory experiment....78

3.2: Experimental Design Principles....79

3.2.1: Between-subjects vs. within-subjects designs....80

3.2.2: Sampling methods and power analysis....80

3.2.3: Common experimental pitfalls....82

3.3: Signal Detection Theory (SDT)....84

3.3.1: Core concepts of signal detection theory....84

3.3.2: SDT distributions....86

3.3.3: ROC curves....87

3.3.4: Applying SDT to the brightness discrimination task....89

3.3.5: Applications of SDT in psychophysics....91

3.4: Statistical Analysis Framework....93

3.4.1: Parametric tests....93

3.4.2: Non-parametric tests....94

3.4.3: Multiple comparisons problem....95

3.5: Psychometric Functions....95

3.5.1: Curve fitting methods....95

3.5.2: Threshold estimation....96

3.5.3: Applications of psychometric functions....98

3.6: Student Exercises....100

3.7: Recommended Reading....100

Chapter 4: Using PsychoPy to Build Experiments....102

4.1: Getting Started with PsychoPy....102

4.2: Example 1: Brightness JND Experiment....103

4.2.1: Design and psychophysical rationale....103

4.2.2: Step-by-step explanation of the brightness JND script....103

4.2.3: Data analysis for brightness JND....112

4.3: Exercise: Building a Serial Memory (PrimacyRecency) Experiment....115

4.3.1: Serial position profiles....122

4.4: Best Practices, Debugging, and Reproducibility....123

4.5: Running Experiments Remotely or in the Lab....124

4.6: Conclusion....124

Answer Keys....126

Bibliography....134

Index....138

Introduction to Psychophysics with Python is a hands-on guide to exploring how we sense and perceive the world—powered by modern Python programming. Bridging classical theory with today’s computational tools, it equips students and researchers to design, run, and analyze psychophysical experiments with confidence.

Starting from the foundations laid by Weber, Fechner, and Stevens, the book traces the evolution of psychophysics into contemporary practice. Readers gain a clear grounding in sensory physiology, experimental design, and statistical analysis, always tied to the central challenge: connecting physical stimuli to perceptual responses and making sense of the data.

What sets this book apart is its practical, step-by-step approach. Through tutorials and annotated code using PsychoPy, readers learn Python essentials—loops, conditionals, data handling—while building real experiments. These skills extend seamlessly into advanced methods like curve fitting, bootstrapping, and statistical inference.

Illustrated with intuitive explanations, diagrams, and thought-provoking exercises, the book blends conceptual clarity with real-world application. By the end, readers will not only understand the principles of psychophysics but also have the coding expertise to create and analyze their own experiments—opening the door to deeper insights into sensation and perception.