P221310 Unit 8

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Participants Twenty-two undergraduates at Carnegie Mellon University in Pittsburgh, Pennsylvania, participated as subjects in the experiments as part of a research methods class. Apparatus and stimuli The stimuli were presented on Dell Professional P2213 22” Widescreen LED LCD monitors, controlled by Dell OptiPlex 9010, 3.4GHz Quad Core computers set to display resolution 1366 x 768 pixels. The first stimulus was a created tone presented through each subjects personal headphones plugged into the tower, at 300 or 900 Hz, ramped on and off gradually. They had to be 16-bit 44.1kHz in order for Eprime to accept them. The second stimulus was a centrally located display of eight digits, presented in two rows of four characters. The digits were selected as follows. First, the highest digit was selected randomly, ranging from 6 to 9. Then, the other seven distractors were selected randomly from the range 1 to the highest digit minus one. This meant that a target on o ne trial could be a distractor on another trial, and ensured no repetitions of the highest digit within a single display. The eight characters were assigned randomly to the fixed positions in the display. The digits and masks measured about 0.3 cm width by 0.4 cm height, and the total display measured 3.9 x 3.0 c m, or 3.72 x 2.86 visual angle, based on a typical viewing distance of two feet. The characters were presented in white on a black background. Design…show more content…
Three different SOAs separated S1 (the tone) and S2 (the digits): 50, 150, and 650 ms. These were used equally often. Each block of 24 trials consisted of 8 trails at each of these three SOA’s, randomly

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