1. Human Perceptual Learning by Mental Imagery
Elisa M. Tartaglia, Laura Bamert, Fred W. Mast, Michael H. Herzog 
Current Biology 
Volume 19, Issue 24, Pages (December 2009)
DOI: /j.cub
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2. Figure 1
Experiment 1
(Aa and Ab) Pretraining baseline measurements. Observers indicated whether the central line of a vertical-line bisection stimulus was offset either to the right or to the left (Aa) or whether the central line was offset upward or downward in the case of a horizontal-line bisection stimulus (Ab).
(B) Training with the vertical bisection stimulus for 4160 trials.
(C) Posttraining baseline measurements (same as in A).
(D) We present results in terms of d′, a criterion-free measure of sensitivity. Higher values of d′ indicate better performance. Posttraining baselines are significantly higher than pretraining baselines (vertical bisection: postbaseline performance − prebaseline performance = 0.78, p = 0.003; horizontal bisection: postbaseline performance − prebaseline performance = 0.45, p = 0.008). The error bars indicate the standard error of the mean (SEM) for eight observers.
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3. Figure 2
Experiment 2
(Aa and Ab) Pretraining baseline measurements. As in experiment 1, observers discriminated between a right and a left offset in the case of a vertical-line bisection stimulus (Aa) and between an upward and a downward offset in the case of a horizontal bisection stimulus (Ab).
(B) Imagery training. Only the two outer lines were presented. Observers were asked to imagine the absent central line to be offset either to the left or to the right, depending on a tone, and to push a button accordingly. We asked observers to imagine the smallest possible offset; the imagined line is indicated by the dashed line (which was not shown in the actual display).
(C) Posttraining baseline measurements.
(D) Sensitivity improved through training for both orientations (vertical bisection: postbaseline performance − prebaseline performance = 0.45, p = 0.01; horizontal bisection: postbaseline performance − prebaseline performance = 0.48, p = ). The error bars indicate the SEM for nine observers.
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4. Figure 3
Experiment 3
(A) Baseline measurements of vertical- and horizontal-line bisection stimuli (identical to the pretraining baselines of experiments 1 and 2).
(B) Second baseline measurements (identical to the posttraining baselines of experiments 1 and 2).
(C) There was no improvement of sensitivity (vertical-line bisection: second baseline performance − first baseline performance = −0.0058, p = 0.7; horizontal-line bisection second baseline performance − first baseline performance = , p = 0.2). The error bars indicate the SEM for ten observers.
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5. Figure 4
Experiment 4
(A) Pretraining baseline measurements for vertical- and horizontal-line bisection stimuli.
(B) Counting lines. As in experiment 2, only the two outer lines were presented. Observers were asked to press the right button when a high-frequency tone was presented and the left button for a low-frequency tone. In addition, observers were asked to count the number of trials with shorter lines (0, 1, or 2 out of 80 trials per block). No imagery was involved in this experiment.
(C) Posttraining baseline measurements.
(D) No improvement of sensitivity occurred through training (vertical-line bisection: postbaseline performance − prebaseline performance = 0.02, p = 0.9; horizontal-line bisection: postbaseline performance − prebaseline performance = 0.05, p = 0.7). The error bars indicate the SEM for six observers.
Current Biology  , DOI: ( /j.cub )
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6. Figure 5
Experiment 5
(Aa and Ab) A vertical (Aa) and a horizontal (Ab) Gabor patch.
(B) Pretraining baseline measurements. The vertical Gabor appeared either in the first interval within a red ring (shown on the left in black) or in the second interval within a green ring (shown on the right in white). Observers indicated in which interval the Gabor was presented. An analogous procedure was used for the horizontal Gabor (not shown).
(C) Imagery training. Observers were presented with two intervals without Gabors. Only the rings were presented. A tone was randomly associated with the first or second interval. Observers were asked to imagine the vertical Gabor in this interval with a contrast as low as possible (dashed Gabor, not shown in the actual display). After the imagery training, we measured baselines for the vertical and horizontal Gabor stimuli once more.
(D) Sensitivity improved for the vertical (postbaseline performance − prebaseline performance = 0.5, p = 0.01) and for the horizontal (postbaseline performance − prebaseline performance = 0.7, p = 0.02) Gabor. The error bars indicate the SEM for five observers.
Current Biology  , DOI: ( /j.cub )
Copyright © 2009 Elsevier Ltd Terms and Conditions