Black Box IEEE 1284 Guia do Utilizador descarregar pdf (Página 40)

Page 40 of 98 The Black Box Toolkit

After DSC has captured a sequence of presentations it is immediately evident that

presentation rates are seriously flawed. On line 3 we can see a bitmap being displayed

and activating the left opto-detector. On line 4 we can see another bitmap activating the

right opto-detector. As can be seen the second bitmap appears 6 refreshes after the first

rather than on the very next refresh as instructed to. Simply there should only have been

10ms difference at 100Hz!

Theoretically a typical TFT would have faired worse due to its nominal 60Hz refresh.

Hence the delay would likely have been at least 99.96ms rather than 16.66ms. Without

use of the BBTK it would be very difficult for the researcher to ensure that a paradigm is

presenting RSVP sequences as intended.

8.2.3. Tutorial 3: Using the BBTK response pad with DSC with a paradigm that

involves visual and auditory presentation

Using the BBTK response pad [optional extra] opens up intriguing possibilities for using

stimulus materials notorious for producing poor timing, e.g. video clips where a small white

block could be unobtrusively superimposed onto the video to act as a marker for the opto-

detector. However in this example we are making use of the audio/visual synchrony check

outlined in tutorial 1. This time however we are using DSC with the BBTK response pad in

order to register exact reaction times relative to any stimulus material. The equipment

setup is identical to that described in tutorial 1 bar that the BBTK response pad is being

used. An active switch closure lead from the pad is tacked to the back of the ‘b’ key on the

keyboard. As a result when the pad button is pressed this will also close the ‘b’ key which

will simultaneously be registered by the experiment generator being used.

Before we begin we need to tell DSC that we will be using the BBTK response pad. Do this

from the “Tools|Options” menu and select “Yes” from “Capture from “BBTK response pad”

menu.

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Black Box IEEE 1284 Guia do Utilizador Página 40