Exploiting that knowledge, in this approach the level of blur of each image is increased to a certain threshold, based on the estimation of a blur measure.
The method proposed in this paper exploits this knowledge by equalizing the level of blur, prior to the actual feature extraction.
To simulate the effects of diminished sensitivity to high spatial frequencies, we blurred our lexical stimuli to various degrees; at a modest level of blur, the words are blurry but recognizable, and at a greater degree, they become entirely unrecognizable.
Comparisons between the two age groups at each level of blur (using a Šidák-corrected alpha of 0.01) showed a significant effect at 4.3 arcminutes (t 30) = 4.14, p < 0.001, d = 1.47, BF 10 = 95.48).
Compared to younger observers, accuracy for older observers dropped to 75% correct at a lower level of blur (2.95 versus 4.43 arcmin; Fig. 2a; see Fig. 2b for threshold by age group and Fig. 2d for exemplar individual participant data).
In the blur condition, we observed a trending difference in the 90% threshold between the two age groups, with older observers' performance dropping to 90% at a lower level of blur compared to younger observers (1.04 versus 2.16 armin, t(29.28) = 2.0, p = 0.06, d = 0.71, BF 10 = 1.47).
By simulating the level of blur or noise that adversely impacts older users, a designer can gain an intuition about what makes text harder or easier for users to read at a glance, even if they would not intentionally blur or degrade the text in their design.
However, the intriguing promise of our results is that by fitting our data to separate psychometric functions for older and younger participants, and then looking at the differences in fitted parameters, we can determine the level of blur or noise required to mimic the experience of an older participant for a younger participant.
This represents the exact opposite trend to the scale invariant nature of static line deviation judgments (Figures 2 and 3) in which performance was directly proportional to the level of blur.
Experiment 2 tells us that, whatever the mechanism involved, it is not tuned to the level of blur in the stimulus a result which is diametrically opposite to that for the static line deviations of Experiment 1.
