************************************************
 Perceiving the Disappearance of Unseen Objects
************************************************

Application Name : "Disappearance Application"
Authors          : Stephen Mitroff & Brian Scholl  (Yale University)
Contact Info     : Stephen.Mitroff@yale.edu, Brian.Scholl@yale.edu


--------------------
 INTRODUCTORY NOTES
--------------------

To use this application, you must be using a Macintosh computer 
running OS 9 either natively, or via 'Classic' emulation from OS X.

You should also be sure that the monitor resolution is set to 1024 x 768.

The demos work best in darkness, so it might help to shut shades and 
turn off the lights.

It may help to run through the steps below in sequence while reading 
these instructions, so consider printing this document out.  (During 
the demos, the program will require the entire screen.)


---------------------------
  STEP #1: EXPERIENCING MIB
---------------------------

To start, you should just try to experience the 'motion-induced 
blindness' (MIB) phenomenon.

To begin, use the mouse to hit the button 'Run Disc'.  You should 
immediately see three things in the middle of the screen: (1) a small 
yellow disc; (2) two small concentric white circles; and (3) a large 
rotating pattern of blue crosses.

Your task is to fixate the central white circles and attend to the 
yellow disc. Throughout the demonstration, you should try to keep 
your eyes as still as possible, fixated on the white circles: if you 
move your eyes, the effect will not work.  While you are fixating, 
you should start to experience MIB: the yellow disc will begin to 
fluctuate in and out of awareness.  In reality, it is never leaving 
the screen.

Practice with this demonstration for a minute until you can reliably 
get MIB episodes to last for around 2 seconds.


----------------------
 QUITTING THE PROGRAM
----------------------

At any point hit 'enter' (or Command-Q) to quit the program.


-------------------------------
 EXTRAS: ADJUSTING SPEED, ETC.
-------------------------------

There are a few hidden options you can use to adjust the display at 
any time.  (Different people sometimes find that they get MIB to last 
longer -- or to occur more frequently -- with different speeds, etc.)

To change the speed of the background motion, press command-3 as you 
watch the moving display.  (To return to the original speed, just 
keep pressing command-3 repeatedly -- the program will cycle through 
5 speeds.)

To change the luminance of the blue rotating pattern, press command-4 
(repeatedly, to cycle through 4 options).

To change the color of the background motion, press command-5 
(repeatedly, to cycle through 4 options).

To change the color of the target disc, press command-6 (repeatedly, 
to cycle through 4 options).


------------------------------------------------------------------
 STEP #2: PERCEIVING THE DISAPPEARANCE OF SOMETHING YOU CAN'T SEE
------------------------------------------------------------------

Once you can reliably experience MIB for around 2 seconds at a time, 
you are ready to move on to the next step.  In our study, we asked 
the following question: What happens if, during MIB, we physically 
remove the yellow disc from the screen?  Since you can't see it 
anyway, during MIB, this is essentially a change from nothing to ... 
nothing.  Nevertheless, most observers are able to see the 
disappearance.

To experience this in the application, you should simply start 
holding down the SHIFT key whenever you experience MIB.  Use the 
following strategy: As soon as you no longer see any yellow, press 
the shift key and do not let go until you see yellow again (or until 
you see a disappearance, explained below).  Whenever you hold down 
the key, the yellow disc will physically disappear 600 ms later. 
(While you are not experiencing MIB, press and hold the shift key so 
you can convince yourself that the disappearance is physically real 
and not due to MIB.)  The yellow disc will remain absent from the 
screen for as long as you are holding down the SHIFT key -- just let 
it go to bring the target back so that you can try again.

At the moment of the physical disappearance, most observers will 
momentarily perceive the disc reappear for just a very brief moment 
as either a dark-blue flash (the 'after-image') or as the yellow disc 
itself (the 'actual-image').  Try it several times!  (Some observers 
notice that pressing the key itself can jolt them out of MIB; 
practice for a minute or so if this happens.)  It helps to attend 
carefully to the location of the disc (while keeping your eyes still, 
fixated on the white circle), even when you can't see it during MIB.


----------------------------
  STEP #3: THE ROTATING LINE
----------------------------

Before moving on to this step, be sure that you can see the 
disappearance as described in the previous step.

Note that the percept triggered by the physical disappearance of the 
disc (in step #2) happens without the physical presence of the disc 
on the screen -- since the signal that triggers the percept is just 
the instantaneous physical disappearance itself!  Instead, this 
percept must be generated from some internal visual representation. 
Now consider: when was this representation stored?  Because the 
yellow disc never changed in the animations you have been viewing so 
far, its representation (that reappears as the flash, coinciding with 
the physical disappearance) could have been stored during the last 
moment of *conscious* experience, just before it disappeared due to 
MIB.  Alternatively, this representation may reflect the state of the 
object *during* MIB, even when you can't see it, just prior to the 
physical disappearance.  We distinguished between these two 
alternatives by changing the object during MIB.

To begin this demonstration, press Command-2.  As soon as you do 
this, the only change you will notice is that the yellow disc will 
turn into a vertical line.  (Note that you can jump back and forth 
between step #2 and step #3 at any time, by pressing Command-1 and 
Command-2.)

Now, when you press the SHIFT key to indicate that you are 
experiencing MIB, the yellow line will disappear 800 ms later, but 
first it will rotate to either the left or right -- so that it is an 
oblique line when it disappears.  You should try to maintain MIB 
through this motion.  This may be difficult at first: the rotation 
might attract your attention, which can cause you to move your eyes, 
disrupting MIB -- so practice for a minute or so at fixating during 
the motion, until you can maintain MIB through the line's motion. 
(You can always let go of the SHIFT key to bring the line back to 
vertical, at which point you can try again.)

In this situation, observers still report perceiving the 
disappearance of the line -- but they always report perceiving the 
*rotated* version of the line (which, when the MIB episode is 
appropriately timed, is something they've never seen before on that 
trial!).  Once you get good at this, you will always know that the 
line will be rotating during MIB, but you'll have no idea what 
direction it moved (since it's a 50/50 choice -- left or right) until 
the physical disappearance, at which point you can experience a 
sudden flash of the 'answer'.  This indicates that visual processing 
of unseen objects continues during MIB, and that this information can 
later reenter awareness.


----------
 FEEDBACK
----------

We would appreciate any feedback you might have about these
demonstrations, at:

Stephen.Mitroff@yale.edu
Brian.Scholl@yale.edu


END OF INSTRUCTIONS.