PXLab Demonstration Experiments

These experiments require a Java Version 5 Virtual Machine. Download and install the Java Runtime Environment Plugin if the respective message appears in the buttons below.

Some of the experiments try to show the resulting data files in a popup window after the experiment has been finished. In order to see them you have to enable your browser to show popup windows from this site. You need not do this if you do not want to see the data files.

Looking for the PXLab Vision Demonstrations? Find them in their own starter file.


The Müller-Lyer Figure

This is a demonstration which combines stimulus object composition and adjustable stimulus parameters. It shows two Müller-Lyer objects. The one on top is the standard and the one on the bottom is an adjustable line only. Adjustment is done with the curosr left/right keys and finished adjustment is indicated with the 'End'-key.


Adaptive Stimulus Control: The Horizontal-Vertical Illusion

This shows adaptive stimulus control as it is used in psychophysical experiments. The design file implements a simple 1-down-1-up-procedure (Levitt, 1971) to find a vertical line which appears to be of the same length as a given horizontal line. The experiment is described in Chapter 3 of Irtel (1991) and is similar to a study by Künnapas (1955).

Künnapas, T. M. (1955). An analysis of the "vertical-horizontal illusion". Journal of Experimental Psychology, 49, 134-140.

Levitt, H. (1971). Transformed up-down methods in psychoacoustics. The Journal of the Acoustical Society of America, 49, 467-476.


Gabor Patterns: The ModelFest Stimuli

This design file presents sinusoidal gratings at various spatial frequencies, amplitudes, and orientations. It shows a complete implementation of the ModelFest stimuli. Note that because of the rather large amplitudes used here for demonstration purposes the nonlinear gamma function of your monitor might make the sinusoids appear to be non-symmetric. This will not be the case when near-threshold amplitudes are used.

The second version of this demo shows static images of the same stimuli. A detailed description of the stimuli may be found at http://vision.arc.nasa.gov/modelfest/stimuli.html.

Here is another gabor pattern demonstration which includes colors and motion.


Sound Discrimination

A simple sound discrimination task which sends data to an E-Mail adress given as an input argument.


A Color Vision Test

This demonstration experiment contains a test for color blindness similar to that suggested by Anstis et al. (1986). It sends its data to an E-Mail address which has to be entered before the experiment starts. The design file is color_vision_test.pxd.

Anstis, S. M., MacLeod, D. A., Cavanagh, P., Lewis, T., Maurer, D., Mather, G. (1986). Computer-generated screening test for colorblindness. Color Research and Application, 11, 63.


Flicker Photometry

This experiment shows adjustment of the luminance of a color stimulus combined with animation. It runs flicker photometry to match the flicker-brightness of two color stimuli.

Wyszecki, G. & Stiles, W. S. (1982). Color science (2nd ed.). Ney York: Wiley.


Color Adjustment

This experiment shows adjustment of a color in 3 dimensions. Adjustment coordinates are the LCh-coordinates of CIELab space. Moving the mouse pointer left/right with the left button down moves the color along the hue circle. Moving the mouse pointer up/down with the left button down increases or decreases the Lightness value. The same moouse motion with the right button down increases or decreases the Chroma coordinate.


Color Selection

The following series of experiments present a sample of colors and allow selection of a single color patch.

This example allows for selection of a single color from an arbitrary sample.

The next example is similar, but here the color sample is a constant Lightness plane of the CIELab color space. In this case the subject also can navigate through CIELab space.

The 3rd example of this series uses a color sample which is the highest Chroma boundary of the Munsell Book of Colors which can be shown on a computer monitor.

Note that the Munsell color patches are simulated here with a D65 illuminant. PXLab can simulate Munsell color patches under any CIE standard illuminant.


Color Transformations

The color_transforms.pxd design file can be used to test PXLab's color transformations.


Apparent Motion

Her is an apparent motion demonstration which presents Wertheimer's apparently moving bar.


Persuit Tracking

This design file creates a persuit tracking experiment. Try to follow the red target dot with your mouse pointer. The resulting data file shows your RMS error in screen pixel units. Note that the target motion is a sum of an arbitrary number of horizontal and vertical sinusoids whose frequency, amplitude, and phase are defined by experimental parameters. The demonstration runs for 20 seconds.


Pulfrich Pendulum Simulation

This design file simulates a pendulum swinging in the horizontal plane. If you have a gray filter for one eye you can observe the Pulfrich-Effect of the pendulum swinging in depth. This demonstration should better be run as an application since it looks much better when vertical retrace synchronization is active.

Pulfrich, C. (1911). Stereoskopisches Sehen und Messen. Jena: Fischer.

Pulfrich C. (1922). Die Stereoskopie im Dienst der isochromen und heterochromen Photometrie. Naturwissenschaften 10, 553-564, 569-574, 596-601, 714-722, 735-743 und 751-761.


Choice Response Time

This shows a left or right arrow and expects a left or right cursor key response. This design file is a short version of an experiment descibed in Chapter 1 of Irtel (1991).

Irtel, H. (1991). Experimentalpsychologisches Praktikum. Heidelberg: Springer.


Ranking Text Items

This shows a list of text items which may be ranked by the subject.


Backward Masking

Shows a white ring as a target signal for response time measurement. The ring is preceded by a white dot in its center. The dot precedes the ring by a varying amount of time (20 to 100 ms). This procedure is similar to that of Werner (1935) and Fehrer and Raab (1962). The subject will not perceive the dot but the response times will show that the dot acts as the response signal. The design file defines 15 trials.

Werner, H. (1935). Studies on contour: I. Qualitative analyses. American Journal of Psychology, 47, 40-64.

Fehrer, E. & Raab, D. (1962). Reaction time to stimuli masked by metacontrast. Journal of Experimental Psychology, 63, 143-147.


Letter Search

This experiment has been created during an on-line presentation at the "Lehr-Lern-Workshop Allgemeine Psychologie" at University of Graz, November 19, 2004. It demonstrates target letter search in a set of distractors.


Stroop Interference

This experiment replicates the Stroop experiment of Chapter 7 in Irtel (1991). It is a non-vocal version of the classical Stroop (1935) task. The number of trials in this design file has been reduced to 12.

Note that PXLab also is able to run the vocal Stroop task by using its built in voice key response mechanism.

Irtel, H. (1991). Experimentalpsychologisches Praktikum. Heidelberg: Springer.

Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643--661.


Change Blindness: The Flicker Method

This experiment demonstrates blindness to stimulus changes across flicker breaks. It is identical in procedure to Experiment 1 of Rensink et al. (1997).

Rensink, R.A., O’Regan, J.K., & Clark, J.J. (1997). To See or Not to See: The Need for Attention to Perceive Changes in Scenes. Psychological Science, 8, 368-373.


Word Recognition on Pseudohomophones

This is a word recognition task with pseudohomophones. It replicates a practical experiment of the University of Nottingham School of Psychology based on Underwood et al (1988).

Underwood, G., Roberts, M.J., & Thomason, H. (1988). Strategical invariance in lexical access: The reappearance of the pseudohomophone effect. Canadian Journal of Psychology, 42, 24-34.


Picture Learning

This experiment first shows black/white and color pictures in a learning list and then runs a recognition memory test with pictures masked by appropriate masking images. It replicates an experiment by Gegenfurtner & Rieger (2000). The SOA between picture and mask is 100 ms.

Gegenfurtner, K.R. & Rieger, J. (2000) Sensory and cognitive contributions of color to the perception of natural scenes. Current Biology, 10, 805-808.


Self-Assessment-Manikin Scales

The file sam.pxd shows several Self-Assessment-Manikin scales (Lang, 1980) combined with text, color and image objects. Scale variants are: 5, 7, and 9 point scales. The 9-point scale my be shown in a reduced form using only 5 images and seperate selection dots. The valence scale my be shown in full body or portrait mode. All images are scalable and can be fit to any size.

The screen shots on the PXLab Self-Assessment-Manikin Scales page also show what can be done with the PXLab SAM tool.

Lang, P. J. (1980). Behavioral treatment and bio-behavioral assessment: computer applications. In J. B. Sidowski, J. H. Johnson, & T. A. Williams (Eds.), Technology in mental health care delivery systems (pp. 119-l37). Norwood, NJ: Ablex.


Big Five Personality Screening

This application shows the 10 item version of the Big Five Inventory developed by Rammstedt & John (2007). The trial data contain the item ratings and the block data contain the scale values for the 5 scales.

Rammstedt, Beatrice & John, Oliver P. (2007). Measuring personality in one minute or less: A 10-item short version of the Big Five Inventory in English and German. Journal of Research in Personality, 41, 203-212.


An Implicit Associations Test

Not a full IAT but a design file which shows how it can be done. This demo is a replication of a demo which may be found at http://implicit.harvard.edu. They call it the 'Age IAT'. This design file is written such that it is easy to plug in all kind of IAT-stories.

Greenwald, A. G., Nosek, B. A., & Banaji, M. R. (2003). Understanding and Using the Implicit Association Test: I. An Improved Scoring Algorithm. Journal of Personality and Social Psychology, 85, 197-216.

Nosek, B. A., Greenwald, A. G., & Banaji, M. R. (2005). Understanding and using the Implicit Association Test: II. Method variables and construct validity. Personality and Social Psychology Bulletin, 31, 166-180.


The Monty Hall Dilemma

This design file is a demonstration of what can be done with PXLab's expression language. It shows trials of the well known Monty Hall dilemma. All rules and restrictions of the game are expressed using PXLab's expression language syntax applied to the parameters of proper display objects.

Here is another link to start the program. This link uses a command line argument to tell the design file that its internal game parameters should be shown to the subject.


Showing Images

The following design file runs a slide show of images from the net.

The same design file can be used to run the program with its display being embedded into an applet frame. This works for all PXLab experiments which can be run as applets.

The following image example allows selection of a single image from a matrix of images.

The next example shows an image and collects a rating scale response. The rating scale contains an adjustable pointer and the final adjustment is signaled by pressing the space bar.


Scalable Vector Graphics (SVG) Images

PXLab can show static Scalable Vector Graphics images. This needs the Apache Software Foundation Batik package being installed. The following examples will download a big (2.8 MB) jar file if Batik is not installed on your system.






Dual Screen Display

If a system has two screens available then PXLab is able to control two monitors. The following design file emulates this on two windows. If this design file is run as an application it should be run with option '-S 6 -w 440 -h 440' on single screen systems and with option '-S 8' on dual screen systems.

This next example shows stereo pictures on a dual screen system with uncrossed disparity viewing. You might not have such a system, but if you do then you can see 3D pictures (use option -S8 for dual screen display).


Response Methods and Objects

PXLab contains several different types of response objects. These are stimulus elements which collect data from the subject in a special way.

This example records the time and position of a mouse button response.

Here is an example for collecting single choice response data.

Here is an example for collecting multiple choice questionnaire data with single selection items.

And this example collects responses on a rating scale.

There is a special response object for text string responses. It collects keyboard input until the RETURN key is pressed.

This design contains GO and NOGO tasks and shows how to control for these.

See response key codes echoed by the key_code.pxd design file. This example also shows how an experiment can be stopped depending upon the subject's response.


Subject Grouping

This design file shows how subject groups are set up and how blocks can be assigned to subject groups. Note that subject groups are treated as covariate factors and the design file lists all possible levels of the covariate factor 'subject group'. The file also defines all other factors of the design in order to automatically create a proper data file.


Sending Data to a Server

PXLab can send data gathered by an applet or by an application to any arbitrary URL. A separate demo file shows how this can be done.


Request Information from a Server

Experiments can set up a HTTP connection to a server and send information to the server or request that some information is being sent back. A separate demo file shows how this can be done.
© H. Irtel, 2008.