Response latency.

<p>(a) Mean response latency as a function of the number of dots. The data of the four younger groups (20–60-yr-old) were combined as shown by a blue curve. For the range of 1 to 6 dots, the latency of the older group is prolonged by 20% when compared with that of the younger group. Note that the symbol legends are listed in panel C. (b) Change in response latency. The latency data is recalculated as percentage change relative to the 20–40-yr-old group mean – positive values indicate longer latencies than the youngest age group, and vice versa. Left panel: numerosity 1 & 2 (subitizing). Right panel: numerosity 4 & 5 (counting). (c) Determination of subitizing span. A bi-linear function was used to fit the mean response latency data, with the intersection point representing the subitizing range. The subitizing speed (the slope before the intersection point) and counting speed (the slope after the intersection point) are both slowed down by 10% in older observers.</p

Counting threshold.

<p>(a) Mean hit rate as a function of the number of dots. A Weibull function was used to fit the data. The curves were gradually displaced to the left with advancing age. Dotted lines show the counting thresholds for two age groups: 21–30- and 61–85-year-old. (b) Mean counting thresholds and standard errors for different age groups. To better display the variation in counting threshold in older adults, the age group 61–85-yr was split into two groups here for visualization: 61–70- yr-old and 71–85-yr-old. (c) Threshold data for individual observers (n = 104) as a function of age. A second-order polynomial function was used to fit the data. Two older observers failed to perform the task for 200 ms, therefore the stimulus duration was increased to 500 ms (dark pink circle: JP) and 700 ms (green circle: CB).</p

Visual stimuli.

<p>The stimulus sequence started with a fixation mark (a), and then a counting target for 200 ms (b), which was then followed by a black-and-white checkerboard mask for another 100 ms (c). Note that the fixation target was presented in a gray background, instead of a white background. (d) An example illustrating the design and physical dimensions of the dot stimulus. The task is to enumerate the number of dots (<i>N</i> = 1–10) in the display, and say the number into a microphone for the measurement of response latency.</p

Counting accuracy.

<p>(a) Mean number of dots reported as a function of the number of dots displayed. In general, a very slight undercounting occurred when there were nine or more dots on the screen. (b) Undercountng/overcounting. The response accuracy data is replotted as signed derivation from the actual numerosity (number of dots reported - number of dots presented). Overcounting (+): more than the number of dots displayed. Undercounting (-): less than the number of dots displayed. Younger observers tend to overcount in the range of 4–6 dots and undercount thereafter, and older observers (red symbols) shows even more over-counting (relatively more positive in magnitude) when the numerosity is greater than 4.</p

Flow diagram of the study.

<p>Flow diagram of the study.</p

Search times during the training paradigm.

<p>In the healthy children of the comparison group, the STs were measured at T1 and T2 without training. The STs did not change by just repeating the task. The patients trained at three different levels of difficulty. The white boxplots show the STs at the beginning, the gray ones at the end of the training period of each level. The medians and IQRs indicate improvement in the patients at all three levels. Outliers were defined as values > 1.5 IQR above the 75% IQR.</p

Schematic representation of the on-screen visual search task during eye tracking.

<p>A: Before each trial, a central cross was presented on a gray background to ensure the subject’s fixation at the center of the screen. A Gabor patch was displayed as an example of the search target: The instruction was “Find the zebra stripes”. B: The children were asked to search the images for the Gabor patch as quickly as possible (here on top of the chimney), and to press the space bar on the keyboard when they found it.</p

The effect of training vs. spontaneous adaptation and natural development by age.

<p>Red and blue circles represent performance before (Pre) and after (Post) training, while color-coded arrows indicate individual ST gains after training. The red line is the linear fit between age and ST before training and represents the spontaneous adaptation and natural development in children with HH. The blue line is the linear fit between age and STs <b>after</b> training. The amount of ST improvement obtained by training (delta Y, blue stippled line) is about 130 s (average over all patients) and could theoretically only be achieved after approximately 6 years of spontaneous adaptation (delta X). The green line represents the STs of the healthy children, showing only a small decrease with natural development. Arrows represent individual improvements of the patients before and after training.</p

Search times during a real life search task in the table test.

<p>The median STs for the patients improve significantly from T1 to T3 with p<0.016. T1 = baseline and before training in patients, T2 = after training in patients, T3 = follow-up after 6 weeks.</p

Demographic and clinical data.

<p>Demographic and clinical data.</p