visual dot probe experiment: position of words & pictures

[Paul Groot]

Hi Nate,

I really don't think that is true. Flat screens have the same kind of
serial refresh mechanism for updating pixels. It's easy to check with
a photo-sensor and oscilloscope. Or if you don't have access to that:
just switch of the onset synchronization in a rapid alternating
black-white sequence:
trial sequence with 3 empty text objects (A,B,C):

A=duration=100ms, prerelease=100, background=black, onset synced
B=duration=[S]ms, prerelease=[S], background=white, onset NOT synced
C=duration=0ms, prerelease=0,background=black,onset synced

Just run those trials in a trial list (N=20) and try values for [S]
which are smaller than the refresh interval.  You can also put the
trial list in a block list with sequential range for the S attribute.

You will see the same kind of horizontal distortions as with CRT
monitors, caused by fragmented screen updates. That would not be
possible with a fast bit-blitting pipeline.  I've even seen this on a
very convincing high-speed movie (@1000Hz) that demonstrated the
serial update for both CRT and TFT displays.

The real difference between CRT and flat screens is that pixel the
intensity curves are really different. CRTs have a very short (but
intense) peak, while flat screens have a very constant intensity.
(That's why CRT's flicker at low refresh rates and LCDs do not.)

Best
Paul

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