MATLAB for Psychologists

1 Basic Operations ..................................................................................... 1
Variables .................................................................................................... 5
Thinking in a Matrix Way ......................................................................... 8
Operations ................................................................................................. 15
Summary ................................................................................................... 17
Exercises ................................................................................................... 18
A Brick for an Experiment ........................................................................ 20
References ................................................................................................. 23
Suggested Readings .................................................................................. 23
2 Data Handling ......................................................................................... 25
Types of Variables (Logical Values, Strings, NaN, Structures, Cells) ...... 25
Logical Variables................................................................................... 25
Strings ................................................................................................... 31
NaN ....................................................................................................... 35
Structures .............................................................................................. 35
Cells ...................................................................................................... 38
Import/Export ............................................................................................ 40
Summary ................................................................................................... 42
Exercises ................................................................................................... 43
A Brick for an Experiment ........................................................................ 44
Read the Results .................................................................................... 44
Reference .................................................................................................. 46
Suggested Readings .................................................................................. 46
3 Plotting Data ............................................................................................ 47
Plot Data .................................................................................................... 47
Control the Plot’s Objects: Labels, Legend, Title… ................................. 50
Subplot: Multiple Plots in One Figure ...................................................... 52
3-D Plots ................................................................................................... 56
Printing and Saving Images ...................................................................... 58
Contents
xii Contents
Handle Graphics ........................................................................................ 58
Summary ................................................................................................... 61
Exercises ................................................................................................... 62
A Brick for an Experiment ........................................................................ 64
Plot the Results ..................................................................................... 64
Reference .................................................................................................. 65
Suggested Readings .................................................................................. 65
4 Start Programming ................................................................................. 67
M-Scripts and Functions ........................................................................... 67
Control Flow Statements........................................................................... 70
Cycles and Conditionals: If ................................................................... 70
Switch Case ........................................................................................... 72
For Loops ............................................................................................. 74
While .................................................................................................... 78
Break ..................................................................................................... 81
Try–Catch ............................................................................................. 82
Loops Versus Matrices and If Versus Logicals ..................................... 82
Functions ................................................................................................... 83
Scope of Variables ................................................................................. 86
Change the Number of Inputs and Outputs ........................................... 87
More on Data Import/Export: Script Examples ........................................ 90
Analysis ................................................................................................ 95
Guidelines for a Good Programming Style ............................................... 96
Writing Code ......................................................................................... 96
Debug .................................................................................................... 98
Summary ................................................................................................... 100
Exercises ................................................................................................... 101
A Brick for an Experiment ........................................................................ 102
Analysis ................................................................................................ 104
References ................................................................................................. 106
Suggested Readings .................................................................................. 106
5 A Better Sound ......................................................................................... 107
Generate a Sound ...................................................................................... 107
Multiple Sounds ........................................................................................ 112
Manipulating a Sound’s Level .................................................................. 114
Match the Level of Sound with Different Waveforms .......................... 115
Stereophonic Sounds for ITD and ILD ..................................................... 116
A Sound’s Envelope .................................................................................. 118
Sound Filtering.......................................................................................... 120
Sound Analysis.......................................................................................... 123
Summary ................................................................................................... 125
Exercises ................................................................................................... 125
Contents xiii
A Brick for an Experiment ........................................................................ 126
References ................................................................................................. 127
Suggested Readings .................................................................................. 128
6 Create and Proccess Images ................................................................... 129
Images Basics ............................................................................................ 129
Importing and Exporting Images .......................................................... 132
Display Images ...................................................................................... 134
Basic Manipulation of Images .................................................................. 135
Point Operations ........................................................................................ 136
Intensity Transformation ....................................................................... 136
Windowing ............................................................................................ 138
Neighborhood Processing ......................................................................... 140
The Edges of the Image ........................................................................ 144
Advanced Image Processing ..................................................................... 144
Creating Images by Computation ............................................................. 144
Summary ................................................................................................... 149
Exercises ................................................................................................... 150
References ................................................................................................. 151
Suggested Readings .................................................................................. 152
7 Data Analysis ........................................................................................... 153
Descriptive Statistics ................................................................................. 153
Measures of Central Tendency .............................................................. 153
Measures of Dispersion ......................................................................... 154
Bivariate and Multivariate Descriptive Statistics ..................................... 155
Covariance ............................................................................................ 156
Simple and Multiple Linear Regression ............................................... 156
Generalized Linear Model .................................................................... 160
Inferential Statistics .................................................................................. 162
Parametric Statistics .............................................................................. 162
t-Test ..................................................................................................... 163
ANOVA ................................................................................................. 166
Nonparametric Statistics ........................................................................... 177
Categorical Data .................................................................................... 177
Ordinal Data .......................................................................................... 179
Signal-Detection Theory (STD) Indexes .............................................. 182
Summary ................................................................................................... 184
Exercises ................................................................................................... 185
A Brick for an Experiment ........................................................................ 186
References ................................................................................................. 187
Suggested Readings .................................................................................. 187
xiv Contents
8 The Charm of Graphical User Interface ............................................... 189
Introduction ............................................................................................... 189
GUIDE ...................................................................................................... 189
Starting GUIDE .................................................................................... 190
The GUI Toolbar ....................................................................................... 190
Adding UiControls to the GUI .............................................................. 191
Closing the GUI .................................................................................... 193
Controlling UiControls from Other UiControls ........................................ 196
The Sum-Two-Numbers Example ........................................................ 196
Displaying Graphs and Figures in the GUI ........................................... 202
Saving User Input ..................................................................................... 204
Adding Your Own Functions ................................................................ 207
A Brick for an Experiment ........................................................................ 212
Appendix ................................................................................................... 215
The File Menu ....................................................................................... 216
The Edit Menu ...................................................................................... 216
The View Menu ..................................................................................... 217
The Layout Menu .................................................................................. 217
Tools Menu ........................................................................................... 218
Help ....................................................................................................... 218
Preferences for GUIDE ............................................................................. 219
Backward Compatibility ....................................................................... 220
Other Preferences .................................................................................. 221
Suggested Readings .................................................................................. 221
9 Psychtoolbox: Video ................................................................................ 223
The Screen Function ................................................................................. 223
Analysis ................................................................................................ 225
How to Use Screen to Get Information ..................................................... 225
How to Use Screen to Draw Figures ......................................................... 227
Preliminary Notions: Drawing Figures in Three Steps—Opening,
Drawing, and Closing ........................................................................... 227
Opening the Window ............................................................................ 227
Drawing: An Introduction ..................................................................... 229
Closing .................................................................................................. 230
Drawing: Reprise ...................................................................................... 230
Analysis ................................................................................................ 231
Drawing Shapes .................................................................................... 231
Batch Processing: Drawing Multiple Figures at Once .............................. 235
Drawing Text ............................................................................................. 236
Importing Images ...................................................................................... 238
Analysis ................................................................................................. 239
Video Clips ................................................................................................ 240
Analysis ................................................................................................. 240
Analysis ................................................................................................. 241
Drawing Things at the Right Time ............................................................ 241
Contents xv
Analysis ................................................................................................. 243
Summary ................................................................................................... 243
Exercises ................................................................................................... 244
Exercise 1 .............................................................................................. 244
Solution 1 .............................................................................................. 244
Exercise 2 .............................................................................................. 244
Solution 2 .............................................................................................. 245
A Brick for an Experiment ........................................................................ 245
References ................................................................................................. 248
Suggested Readings .................................................................................. 248
10 Psychtoolbox: Sound, Keyboard and Mouse ........................................ 249
Timing ....................................................................................................... 249
Priority ...................................................................................................... 250
Sound Functions........................................................................................ 251
Getting Participants’ Inputs: Keyboard and Mouse Functions ................. 253
Keyboard Response .............................................................................. 253
“Press Any Key to Proceed” ................................................................. 254
“Press the Spacebar to Proceed” ........................................................... 254
“Press Any Key to Respond” ................................................................ 256
Reaction-Time Detection ...................................................................... 256
Choice Reaction Time ........................................................................... 258
Go/No-Go Reaction Time ..................................................................... 259
Reaction Times Within a Video Clip..................................................... 260
Mouse Input .......................................................................................... 262
Using Participants’ Input to Manipulate Shape Characteristics ................ 263
Keyboard Manipulations ....................................................................... 264
Placing Discs with the Mouse ............................................................... 266
Summary ................................................................................................... 267
Exercises ................................................................................................... 268
Exercise 1 ............................................................................................. 268
A Brick for an Experiment ........................................................................ 269
References ................................................................................................. 272
Suggested Readings .................................................................................. 273
About the Authors ........................................................................................... 275
Index ................................................................................................................ 277