Visual search has been a long-standing problem in applications such as location recognition and product search. Much research has been done on image representation, matching, indexing, and retrieval. Key component tec...Visual search has been a long-standing problem in applications such as location recognition and product search. Much research has been done on image representation, matching, indexing, and retrieval. Key component technologies for visual search have been developed, and numerous real-world applications are emerging. To ensure application interoperability, the Moving Picture Experts Group （MPEG） has begun standardizing visuaJ search technologies and is developing the compact descriptors for visua） search （CDVS） standard. MPEG seeks to develop a collaborative platform for evaluating existing visual search technologies. Peking University has participated in this standardization since the 94th MPEG meeting, and significant progress has been made with the various proposals. A test model （TM） has been selected to determine the basic pipeline and key components of visual search. However, the first-version TM has high computational complexity and imperfect retrieval and matching. Core experiments have therefore been set up to improve TM. In this article, we summarize key technologies for visual search and report the progress of MPEG CDVS. We discuss Peking University＇ s efforts in CDVS and also discuss unresolved issues.展开更多
Active exploratory behaviors have often been associated with theta oscillations in rodents,while theta oscillations during active exploration in non-human primates are still not well understood.We recorded neural acti...Active exploratory behaviors have often been associated with theta oscillations in rodents,while theta oscillations during active exploration in non-human primates are still not well understood.We recorded neural activities in the frontal eye field(FEF)and V4 simultaneously when monkeys performed a free-gaze visual search task.Saccades were strongly phase-locked to theta oscillations of V4 and FEF local field potentials,and the phase-locking was dependent on saccade direction.The spiking probability of V4 and FEF units was significantly modulated by the theta phase in addition to the time-locked modulation associated with the evoked response.V4 and FEF units showed significantly stronger responses following saccades initiated at their preferred phases.Granger causality and ridge regression analysis showed modulatory effects of theta oscillations on saccade timing.Together,our study suggests phase-locking of saccades to the theta modulation of neural activity in visual and oculomotor cortical areas,in addition to the theta phase locking caused by saccade-triggered responses.展开更多
Background:It has been suggested that older adults show a reduced attentional field compared to younger adults.This may be attributed to a poorer utilization of peripheral vision(i.e.,peripheral attentional allocation...Background:It has been suggested that older adults show a reduced attentional field compared to younger adults.This may be attributed to a poorer utilization of peripheral vision(i.e.,peripheral attentional allocation)and a higher reliance on central vision compared to younger adults.To test this,we examined the importance of central,peri-foveal and near periphery information in younger and older adults by comparing their visual search performance while their central vision was blocked,in the presence of different sized artificial central scotomas.We tested participants in two versions of visual search,pop-out and serial search,because they require a different use of central and peripheral attention.Pop-out search relies on processing of the entire visual scene(i.e.,global processing)whereas serial search requires processing of each feature serially(i.e.,local processing).Methods:Thirteen healthy younger(M=21.8,SD=1.5)and 15 older adults(M=69.1 years,SD=7.3)performed a pop-out and a serial version of a visual search task in the presence of different sized gaze-contingent artificial central scotomas(no scotoma,3°diameter,5°and 7°).Participants were asked to indicate as quickly as possible whether a target was present or not among distractors whose number varied(16,32 or 64 objects).Results:We found evidence for a greater decline in peripheral processing in older adults compared to younger in pop-out but not in serial search.For the pop-out condition with no scotoma,we found that the further the target in the periphery,the longer the search time,and that this increase was proportionally greater for older adults compared to younger adults.Further,increases in scotoma size were associated with a greater increase in reaction times for older adults compared to younger participants.For the serial condition,both groups showed similar increases in reaction times with target distance from center and scotoma size.We surmise that this may be due to task difficulty in serial search;central vision is necessary for both groups.Conclusions:In conclusion,these findings suggest that,in global processing,older adults distribute more resources towards central vision compared to younger adults.展开更多
Background:Age related macular degeneration(AMD)is one of the main causes of vision loss in older adults,generating,in most cases,a central scotoma that reduces central visual acuity(Noble&Chaudhary,2010).People a...Background:Age related macular degeneration(AMD)is one of the main causes of vision loss in older adults,generating,in most cases,a central scotoma that reduces central visual acuity(Noble&Chaudhary,2010).People affected by AMD have to rely on peripheral visual information and would highly benefit from efficiently allocating their attention to the periphery.Indeed,attention can improve peripheral spatial resolution(Carrasco,Ling&Read,2004)and can be allocated to a certain expanse of space outside of the central visual span,known as the attentional span.Attentional span has been shown to be decreased in people with AMD with less attention allocated to the periphery and more to the central visual field(Cheong et al.,2008),however it remains unknown whether aging is also a contributing factor.Methods:Fourteen healthy younger(mean age=21.8 years,SD=1.5)and 8 older adults(mean age=69.6 years,SD=7.3)performed a pop-out and a serial version of a visual search task,in the presence of different sized gaze-contingent invisible and visible artificial central scotomata(no scotoma,3°diameter,5°and 7°).Participants were asked to indicate as quickly as possible whether a target was present or not among distractors whose number varied(16,32 or 64 objects).We wished to determine whether the size of the scotoma,occluding different degrees of central vision,affected visual search differently for younger vs.older participants.Results:Both the younger and older participants showed higher reaction times(RTs)to find the target for the serial version(M=2,074 ms for younger adults,M=3,853 ms for older adults)compared to the pop-out version(M=866 ms,M=1,475 ms,P<0.001)and for more distractors(32 distractors compared to 16,and 64 compared to 32,P<0.01).Older adults showed longer RTs than younger adults for both versions of the task(P<0.01).We found a significant effect of scotoma size on older adults(3°scotoma M=3,276 ms;7°scotoma M=3,877 ms,P<0.05),however,accurate performance was higher with no scotoma(96%vs.92%,P<0.05)in the pop-out search task.This suggests that older participants privileged a fast decision at the expense of performance in those cases.For the younger adults,RTs were higher in the serial search task in the presence of a scotoma(M=2,074 ms)compared to the control condition(M=1,665 ms,P>0.05).Conclusions:These results suggest that older adults take longer to perform visual search compared to younger adults and tend to use peripheral visual less than younger adults;larger central scotomas disrupted their performance but not that of younger participants,who performed equally well with different central scotoma sizes.These findings suggest that aging is a contributing factor in the decrease of the peripheral attentional span.展开更多
In order to discuss the efficiency of visual search of the taekwondo athletes with different kinds of trait anxieties, this article has selected 30 taekwondo athletes with high trait anxieties and another 30 ones with...In order to discuss the efficiency of visual search of the taekwondo athletes with different kinds of trait anxieties, this article has selected 30 taekwondo athletes with high trait anxieties and another 30 ones with low trait anxieties as the testees so as to conduct respective investigations on their visual search reaction time and accuracy of reaction. The results show that the reaction time of individuals with high trait anxieties is significantly longer than that of the individuals with low trait anxieties; the reaction time under threatening stimuli is significantly longer than that under no conditions of threatening stimuli; the reaction accuracy rate of visual search reaction of taekwondo athletes under threatening stimuli is significantly lower than that under no threatening stimuli.展开更多
Information flow between the prefrontal and visual cortices is critical for visual behaviors such as visual search. To investigate its mechanisms, we simultaneously recorded spike and local field potential (LFP) signa...Information flow between the prefrontal and visual cortices is critical for visual behaviors such as visual search. To investigate its mechanisms, we simultaneously recorded spike and local field potential (LFP) signals in the frontal eye field (FEF) and area V4 while monkeys performed a free-gaze visual search task. During free-gaze search, spike-LFP coherence between FEF and V4 was enhanced in the theta rhythm (4–8 Hz) but suppressed in the alpha rhythm (8–13 Hz). Cross-frequency couplings during the Cue period before the search phase were related to monkey performance, with higher FEF theta-V4 gamma coupling and lower FEF alpha-V4 gamma coupling associated with faster search. Finally, feature-based attention during search enhanced spike-LFP coherence between FEF and V4 in the gamma and beta rhythms, whereas overt spatial attention reduced coherence at frequencies up to 30 Hz. These results suggest that oscillatory coupling may play an important role in mediating interactions between the prefrontal and visual cortices during visual search.展开更多
Smartphones are becoming increasingly popular, users are provided with various interface styles with different designed icons. Icon, as an important competent of user interface, is regarded to be more efficient and pl...Smartphones are becoming increasingly popular, users are provided with various interface styles with different designed icons. Icon, as an important competent of user interface, is regarded to be more efficient and pleasurable. However, compared with desktop computers, fewer design principles on smartphone icon were proposed. This paper investigated the effects of icon background shape and the figure/background area ratio on visual search performance and user preference. Icon figures combined with six different geometric background shapes and five different figure/ background area ratios were studied on three different screens in experiments with 40 subjects. The results of an analysis of variance （ANOVA） showed that these two inde- pendent variables （background shape and figure/background area ratio） significantly affected the visual search performance and user preference. On 3.5-in （1 in=0.025 4 m） and 4.0-in displays, unified backgroundwould be optimal, shapes such as square, circle and transitions between them （e.g., rounded square, squircle, etc.） are recommended because backgrounds in these shapes yield a better search time performance and subjective satisfaction for ease of use, search and visual preference. A 60% figure/background area ratio is the most appropriate for smartphone icon design on the 3.5-in screen, while a 50% area ratio could be a suggestion for both relatively optimized search performance and user preference on 4.0-in. In terms of the 4.7-in, icon figure is used di- rectly for its better performance and preference compared with icons with background.展开更多
The study investigated user experience, display complexity, display type (tables versus graphs), and task difficulty as variables affecting the user’s ability to navigate through complex visual data. A total of 64 pa...The study investigated user experience, display complexity, display type (tables versus graphs), and task difficulty as variables affecting the user’s ability to navigate through complex visual data. A total of 64 participants, 39 undergraduate students (novice users) and 25 graduate students (intermediate-level users) participated in the study. The experimental design was 2 × 2 × 2 × 3 mixed design using two between-subject variables (display complexity, user experience) and two within-subject variables (display format, question difficulty). The results indicated that response time was superior for graphs (relative to tables), especially when the questions were difficult. The intermediate users seemed to adopt more extensive search strategies than novices, as revealed by an analysis of the number of changes they made to the display prior to answering questions. It was concluded that designers of data displays should consider the (a) type of display, (b) difficulty of the task, and (c) expertise level of the user to obtain optimal levels of performance.展开更多
It is argued that research on eye movements has now entered a fourth general era. Each of the four eras is briefly reviewed, and research findings related to eye movements during reading, scene perception, and visual ...It is argued that research on eye movements has now entered a fourth general era. Each of the four eras is briefly reviewed, and research findings related to eye movements during reading, scene perception, and visual search are discussed. Future directions for research in each of these areas and research in other domains involving eye movements are also discussed.展开更多
In this paper, a method to initiate, develop and visualize an abstract syntax tree (AST) in C++ source code is presented. The approach is in chronological order starting with collection of program codes as a string an...In this paper, a method to initiate, develop and visualize an abstract syntax tree (AST) in C++ source code is presented. The approach is in chronological order starting with collection of program codes as a string and split into individual characters using regular expression. This will be followed by separating the token grammar using best first search (BFS) algorithm to determine node having lowest value, lastly followed by graph presentation of intermediate representation achieved with the help of graph visualization software (GraphViz) while former is implemented using python programming language version 3. The efficacy of our approach is used in analyzing C++ code and yielded a satisfactory result.展开更多
基金supported by National Basic Research "(973") Program of China(2009CB320902)the Chinese National Nature Science Foundation (60902057)
文摘Visual search has been a long-standing problem in applications such as location recognition and product search. Much research has been done on image representation, matching, indexing, and retrieval. Key component technologies for visual search have been developed, and numerous real-world applications are emerging. To ensure application interoperability, the Moving Picture Experts Group （MPEG） has begun standardizing visuaJ search technologies and is developing the compact descriptors for visua） search （CDVS） standard. MPEG seeks to develop a collaborative platform for evaluating existing visual search technologies. Peking University has participated in this standardization since the 94th MPEG meeting, and significant progress has been made with the various proposals. A test model （TM） has been selected to determine the basic pipeline and key components of visual search. However, the first-version TM has high computational complexity and imperfect retrieval and matching. Core experiments have therefore been set up to improve TM. In this article, we summarize key technologies for visual search and report the progress of MPEG CDVS. We discuss Peking University＇ s efforts in CDVS and also discuss unresolved issues.
基金We are grateful for the financial support from the National Natural Science Foundation of China(31671108 and 31800900)the National Key R&D Program of China(2017YFC1307500)+1 种基金the Shenzhen Science and Technology Innovation Commission(JCYJ20180508152240368)the Shenzhen Basic Research Program(JCYJ20200109114805984).
文摘Active exploratory behaviors have often been associated with theta oscillations in rodents,while theta oscillations during active exploration in non-human primates are still not well understood.We recorded neural activities in the frontal eye field(FEF)and V4 simultaneously when monkeys performed a free-gaze visual search task.Saccades were strongly phase-locked to theta oscillations of V4 and FEF local field potentials,and the phase-locking was dependent on saccade direction.The spiking probability of V4 and FEF units was significantly modulated by the theta phase in addition to the time-locked modulation associated with the evoked response.V4 and FEF units showed significantly stronger responses following saccades initiated at their preferred phases.Granger causality and ridge regression analysis showed modulatory effects of theta oscillations on saccade timing.Together,our study suggests phase-locking of saccades to the theta modulation of neural activity in visual and oculomotor cortical areas,in addition to the theta phase locking caused by saccade-triggered responses.
文摘Background:It has been suggested that older adults show a reduced attentional field compared to younger adults.This may be attributed to a poorer utilization of peripheral vision(i.e.,peripheral attentional allocation)and a higher reliance on central vision compared to younger adults.To test this,we examined the importance of central,peri-foveal and near periphery information in younger and older adults by comparing their visual search performance while their central vision was blocked,in the presence of different sized artificial central scotomas.We tested participants in two versions of visual search,pop-out and serial search,because they require a different use of central and peripheral attention.Pop-out search relies on processing of the entire visual scene(i.e.,global processing)whereas serial search requires processing of each feature serially(i.e.,local processing).Methods:Thirteen healthy younger(M=21.8,SD=1.5)and 15 older adults(M=69.1 years,SD=7.3)performed a pop-out and a serial version of a visual search task in the presence of different sized gaze-contingent artificial central scotomas(no scotoma,3°diameter,5°and 7°).Participants were asked to indicate as quickly as possible whether a target was present or not among distractors whose number varied(16,32 or 64 objects).Results:We found evidence for a greater decline in peripheral processing in older adults compared to younger in pop-out but not in serial search.For the pop-out condition with no scotoma,we found that the further the target in the periphery,the longer the search time,and that this increase was proportionally greater for older adults compared to younger adults.Further,increases in scotoma size were associated with a greater increase in reaction times for older adults compared to younger participants.For the serial condition,both groups showed similar increases in reaction times with target distance from center and scotoma size.We surmise that this may be due to task difficulty in serial search;central vision is necessary for both groups.Conclusions:In conclusion,these findings suggest that,in global processing,older adults distribute more resources towards central vision compared to younger adults.
文摘Background:Age related macular degeneration(AMD)is one of the main causes of vision loss in older adults,generating,in most cases,a central scotoma that reduces central visual acuity(Noble&Chaudhary,2010).People affected by AMD have to rely on peripheral visual information and would highly benefit from efficiently allocating their attention to the periphery.Indeed,attention can improve peripheral spatial resolution(Carrasco,Ling&Read,2004)and can be allocated to a certain expanse of space outside of the central visual span,known as the attentional span.Attentional span has been shown to be decreased in people with AMD with less attention allocated to the periphery and more to the central visual field(Cheong et al.,2008),however it remains unknown whether aging is also a contributing factor.Methods:Fourteen healthy younger(mean age=21.8 years,SD=1.5)and 8 older adults(mean age=69.6 years,SD=7.3)performed a pop-out and a serial version of a visual search task,in the presence of different sized gaze-contingent invisible and visible artificial central scotomata(no scotoma,3°diameter,5°and 7°).Participants were asked to indicate as quickly as possible whether a target was present or not among distractors whose number varied(16,32 or 64 objects).We wished to determine whether the size of the scotoma,occluding different degrees of central vision,affected visual search differently for younger vs.older participants.Results:Both the younger and older participants showed higher reaction times(RTs)to find the target for the serial version(M=2,074 ms for younger adults,M=3,853 ms for older adults)compared to the pop-out version(M=866 ms,M=1,475 ms,P<0.001)and for more distractors(32 distractors compared to 16,and 64 compared to 32,P<0.01).Older adults showed longer RTs than younger adults for both versions of the task(P<0.01).We found a significant effect of scotoma size on older adults(3°scotoma M=3,276 ms;7°scotoma M=3,877 ms,P<0.05),however,accurate performance was higher with no scotoma(96%vs.92%,P<0.05)in the pop-out search task.This suggests that older participants privileged a fast decision at the expense of performance in those cases.For the younger adults,RTs were higher in the serial search task in the presence of a scotoma(M=2,074 ms)compared to the control condition(M=1,665 ms,P>0.05).Conclusions:These results suggest that older adults take longer to perform visual search compared to younger adults and tend to use peripheral visual less than younger adults;larger central scotomas disrupted their performance but not that of younger participants,who performed equally well with different central scotoma sizes.These findings suggest that aging is a contributing factor in the decrease of the peripheral attentional span.
文摘In order to discuss the efficiency of visual search of the taekwondo athletes with different kinds of trait anxieties, this article has selected 30 taekwondo athletes with high trait anxieties and another 30 ones with low trait anxieties as the testees so as to conduct respective investigations on their visual search reaction time and accuracy of reaction. The results show that the reaction time of individuals with high trait anxieties is significantly longer than that of the individuals with low trait anxieties; the reaction time under threatening stimuli is significantly longer than that under no conditions of threatening stimuli; the reaction accuracy rate of visual search reaction of taekwondo athletes under threatening stimuli is significantly lower than that under no threatening stimuli.
基金supported by the National Key R&D Program of China(2017YFC1307500)the National Natural Science Foundation of China(31800900)+2 种基金the CAS-Iranian Vice presidency for Science and Technology Joint Research Project(172644KYSB20160175)Guangdong Innovative and Entrepreneurial Research Team Program(2014ZT05S020)Shenzhen Municipal Grants(KQJSCX20170731164702657,JCYJ20151030140325151,JCYJ20170413165053031,GJHZ20160229200136090,KQTD20140630180249366)
文摘Information flow between the prefrontal and visual cortices is critical for visual behaviors such as visual search. To investigate its mechanisms, we simultaneously recorded spike and local field potential (LFP) signals in the frontal eye field (FEF) and area V4 while monkeys performed a free-gaze visual search task. During free-gaze search, spike-LFP coherence between FEF and V4 was enhanced in the theta rhythm (4–8 Hz) but suppressed in the alpha rhythm (8–13 Hz). Cross-frequency couplings during the Cue period before the search phase were related to monkey performance, with higher FEF theta-V4 gamma coupling and lower FEF alpha-V4 gamma coupling associated with faster search. Finally, feature-based attention during search enhanced spike-LFP coherence between FEF and V4 in the gamma and beta rhythms, whereas overt spatial attention reduced coherence at frequencies up to 30 Hz. These results suggest that oscillatory coupling may play an important role in mediating interactions between the prefrontal and visual cortices during visual search.
基金Acknowledgements This research was supported by the National Natural Science Foundation of China （Grant No. 51175458）.
文摘Smartphones are becoming increasingly popular, users are provided with various interface styles with different designed icons. Icon, as an important competent of user interface, is regarded to be more efficient and pleasurable. However, compared with desktop computers, fewer design principles on smartphone icon were proposed. This paper investigated the effects of icon background shape and the figure/background area ratio on visual search performance and user preference. Icon figures combined with six different geometric background shapes and five different figure/ background area ratios were studied on three different screens in experiments with 40 subjects. The results of an analysis of variance （ANOVA） showed that these two inde- pendent variables （background shape and figure/background area ratio） significantly affected the visual search performance and user preference. On 3.5-in （1 in=0.025 4 m） and 4.0-in displays, unified backgroundwould be optimal, shapes such as square, circle and transitions between them （e.g., rounded square, squircle, etc.） are recommended because backgrounds in these shapes yield a better search time performance and subjective satisfaction for ease of use, search and visual preference. A 60% figure/background area ratio is the most appropriate for smartphone icon design on the 3.5-in screen, while a 50% area ratio could be a suggestion for both relatively optimized search performance and user preference on 4.0-in. In terms of the 4.7-in, icon figure is used di- rectly for its better performance and preference compared with icons with background.
文摘The study investigated user experience, display complexity, display type (tables versus graphs), and task difficulty as variables affecting the user’s ability to navigate through complex visual data. A total of 64 participants, 39 undergraduate students (novice users) and 25 graduate students (intermediate-level users) participated in the study. The experimental design was 2 × 2 × 2 × 3 mixed design using two between-subject variables (display complexity, user experience) and two within-subject variables (display format, question difficulty). The results indicated that response time was superior for graphs (relative to tables), especially when the questions were difficult. The intermediate users seemed to adopt more extensive search strategies than novices, as revealed by an analysis of the number of changes they made to the display prior to answering questions. It was concluded that designers of data displays should consider the (a) type of display, (b) difficulty of the task, and (c) expertise level of the user to obtain optimal levels of performance.
文摘It is argued that research on eye movements has now entered a fourth general era. Each of the four eras is briefly reviewed, and research findings related to eye movements during reading, scene perception, and visual search are discussed. Future directions for research in each of these areas and research in other domains involving eye movements are also discussed.
文摘In this paper, a method to initiate, develop and visualize an abstract syntax tree (AST) in C++ source code is presented. The approach is in chronological order starting with collection of program codes as a string and split into individual characters using regular expression. This will be followed by separating the token grammar using best first search (BFS) algorithm to determine node having lowest value, lastly followed by graph presentation of intermediate representation achieved with the help of graph visualization software (GraphViz) while former is implemented using python programming language version 3. The efficacy of our approach is used in analyzing C++ code and yielded a satisfactory result.
