Abstract
The efficiency of visual tasks involving localization has traditionally been evaluated using forced choice experiments that capitalize on independence across locations to simplify the performance of the ideal observer. However, developments in ideal observer analysis have shown how an ideal observer can be defined for free-localization tasks, where a target can appear anywhere in a defined search region and subjects respond by localizing the target. Since these tasks are representative of many real-world search tasks, it is of interest to evaluate the efficiency of observer performance in them. The central question of this work is whether humans are able to effectively use the information in a free-localization task relative to a similar task where target location is fixed. We use a yes-no detection task at a cued location as the reference for this comparison. Each of the tasks is evaluated using a Gaussian target profile embedded in four different Gaussian noise backgrounds having power-law noise power spectra with exponents ranging from 0 to 3. The free localization task had a square 6.7° search region. We report on two follow-up studies investigating efficiency in a detect-and-localize task, and the effect of processing the white-noise backgrounds. In the fixed-location detection task, we find average observer efficiency ranges from 35 to 59% for the different noise backgrounds. Observer efficiency improves dramatically in the tasks involving localization, ranging from 63 to 82% in the forced localization tasks and from 78 to 92% in the detect-and- localize tasks. Performance in white noise, the lowest efficiency condition, was improved by filtering to give them a power-law exponent of 2. Classification images, used to examine spatial frequency weights for the tasks, show better tuning to ideal weights in the free-localization tasks. The high absolute levels of efficiency suggest that observers are well-adapted to free-localization tasks.
Highlights
The concept of calculation efficiency, which we refer to as efficiency, in the presence of image noise has been used extensively as a method for understanding visual processing since its seminal introduction by Barlow (Barlow, 1977, 1978; Barlow and Reeves, 1979)
To investigate the effect of a detection criterion on free-localization tasks, we evaluated a detect-and localize (D&L) task, in which the target profile appeared at a random location in the search region in 50% of the trials, and was not present in the other 50% if the trials
SUMMARY AND CONCLUSIONS We find human observers substantially improve in performance relative to the ideal observer in free-localization tasks compared to fixed-location detection tasks, in spite of increased contrast thresholds
Summary
The concept of calculation efficiency, which we refer to as efficiency, in the presence of image noise has been used extensively as a method for understanding visual processing since its seminal introduction by Barlow (Barlow, 1977, 1978; Barlow and Reeves, 1979). The use of the ideal observer as yardstick for human performance implicitly controls for the relevant information present in stimuli used to perform a task. This topic has a long history in vision science, as well as areas of applied vision such as medical imaging. In the realm of vision science, there are many examples where efficiency is used to reveal the presence (or absence) of limitations and constraints in visual processing (Barlow, 1978; Barlow and Reeves, 1979; Burgess et al, 1981; Pelli, 1985; Legge et al, 1987; Geisler, 1989; Tjan et al, 1995). Efficiency is used to identify opportunities for image processing or other methodological changes that lead to improved performance in visual tasks (Myers et al, 1985; Wagner and Brown, 1985; Insana and Hall, 1994; Siewerdsen and Jaffray, 2000; Abbey et al, 2006)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
