Figure 1.
Effects of Stimulus Rhythm and ITI on Perceptual Learning of Multiple Contrast Discrimination
(A) Illustration of a 2AFC trial in a contrast discrimination task. The observers judged which interval contained the higher contrast stimulus.
(B) Learning effects under the 1-s constant ITI condition from our previous study [3]. In this and other plots throughout the paper, data points below the red diagonal lines indicate learning. Error bars indicate s.e.m. ΔC indicates contrast threshold.
(C and D) Learning effects under 2-s constant (F1,5 = 89.9, p < 0.001; repeated measures ANOVA) and jittered (F1,5 = 0.08, p = 0.789) ITI conditions, respectively. In these and later plots, the gray dashed line indicates the mean PPR.
(E and F) Learning effects under 3-s constant (F1,5 = 84.8, p < 0.001) (E) and jittered (F1,5 = 0.08, p = 0.786) ITI conditions (F).
(G) Post- versus pre-training contrast thresholds with an uneven rhythm (neighboring ITIs = 2, 2.5, 1.5, and 1 s; F1,5 = 1.22, p = 0.320).
(H) Post- versus pre-training contrast thresholds with a lengthening rhythm (neighboring ITIs = 1.25, 1.75, 2.25, and 2.75 s; F1,5 = 8.22, p = 0.032).
(I) A summary of the learning effects in (B–H). Each bar represents the mean PPR over all four contrast conditions and all observers in the corresponding plot, as indicated along the x-axis. Previous result with 1-s ITI (blue colored) [3] was also plotted here for reference.
(J and K) Averaged within- and between-session contrast threshold changes under 2-s constant and jittered ITI conditions (see C and D), respectively, for each reference contrast and the overall means across all reference contrasts. Each data point represents one interleaved staircase run, and each session contains five consecutive runs.
Figure 2.
The Effects of Roving After Each Training Session on Perceptual Learning
(A–D) Post- versus pre-training contrast thresholds in practice conditions in which each regular temporal-patterned training session was followed by roving interference after a delay of (A) 0 h (F1,5 = 1.48, p = 0.278), (B) 4 h (F1,5 = 10.6, p = 0.022), (C) 8 h (F1,5 = 42.0, p = 0.001), and (D) 12 h (F1,5 = 13.1, p = 0.015).
(E) PPR as a function of the delay of roving interference. The horizontal line indicates the PPR in regular temporal-patterned training without followed roving interference (Figure 1B).
Figure 3.
The Effects of Stimulus Roving After Learning
(A) Stimulus roving immediately after completion of temporal-patterned training. The left panel shows pre- versus post-training thresholds. The middle panel shows first roving session versus post-training thresholds (F1,5 = 0.24, p = 0.647). Notice that the y-axis in the left panel becomes x-axis in the middle and right panels. The right panel shows the fourth (last) roving session versus post-training thresholds (F1,4 = 0.49, p = 0.520; only five observers finished all four roving sessions).
(B) Same as (A) except that roving sessions started 2–4 wk after temporal-patterned training. The left panel shows pre- versus post-training thresholds. The middle panel shows first roving session versus post-training thresholds (F1,2 = 0.46, p = 0.570). Notice that the y-axis in the left panel becomes x-axis in the middle and right panels. The right panel shows the fourth (last) roving session versus post-training thresholds (F1,2 = 2.36, p = 0.264).
Figure 4.
The Minimal Block Size for Perceptual Learning of Multiple Stimuli
(A–C) Post- versus pre-training contrast thresholds with each roving contrast practiced (A) every three consecutive trials (F1,5 = 0.60, p = 0.474), (B) five consecutive trials (F1,5 = 9.26, p = 0.029), and (C) eight consecutive trials (F1,5 = 53.9, p = 0.001).
(D) Summary of learning effects in various block-size conditions. Data for one-trial and 30-trial block-size conditions (blue symbols) had been reported previously [6] and were used here for reference. Each datum represents the mean PPR over four contrast conditions and all observers.
Figure 5.
Cases in Which Learning was Undisturbed by Stimulus Roving (Except (A))
(A) Post- versus pre-training contrast thresholds for four roving contrasts with longer stimulus duration at 400 ms (F1,3 = 3.29, p = 0.167).
(B) Post- versus pre-training contrast thresholds for (left) a more similar pair of roving contrasts (0.30 and 0.47; F1,5 = 0.79, p = 0.414) and (right) a more distinct pair of roving contrasts (0.20 and 0.47; F1,5 = 23.2, p = 0.005).
(C) Post- versus pre-training contrast thresholds for four roving contrasts with pre-trial letter cues for their temporal identities (F1,5 = 34.7, p = 0.002).
(D) Perceptual learning of orientation discrimination for illusory line stimuli (far left). Post- and pre-training orientation thresholds were compared for (middle left) the temporal patterning condition (F1,5 = 27.7, p = 0.003), (middle right) roving condition (F1,5 = 0.61, p = 0.472), and (far right) roving conditions with four cardinal or oblique orientations (F1,5 = 40.8, p = 0.001). Thresholds for cardinal orientations (green and purple symbols) were lower than those for oblique orientations (blue and yellow symbols), showing a classical oblique effect.