The aim of the study is to understand the selection process, that modulates the exploration mechanism, during the execution of a high cognitively demanding task. The main purpose is to identify the mechanism competition mechanism between top-down and bottom-up. We developed an adaptive system trying to emulate this mechanism.

1. THE ROLE OF LATEST FIXATIONS ON ONGOING VISUAL
SEARCH
A MODEL TO EVALUATE THE SELECTION MECHANISM
Giacomo Veneri, Pamela Federighi,Francesca Rosini, Elena
Pretegiani, Antonio Federico, Alessandra Rufa
Eye tracking & Vision Applications Lab (EVA Lab) Department of Neurological Neurosurgical and Behavioral Science
University of Siena, Italy
07/01/13 www.evalab.unisi.it 1

2. Outline
• Top-Down vs Bottom-Up on ongoing visual
search
• Efficiency on Visual search
• (Bayesian) Model on visual search
07/01/13 www.evalab.unisi.it 2

3. Task
 “Visual Search depends
on sensory, perceptual
and cognitive processes”
[colby 2009]
 Il TMT misuar la capcità
di esplorare ed eseguire
una sequenza in modo
corretto
 TMTB è un mappa
viariante in cui i target
diventano distrattori
[Wolwer 2003]
07/01/13 www.evalab.unisi.it 3

4. Mathematical Method Fixations
07/01/13 www.evalab.unisi.it 4

5. Direction vs Previous fixations
In order to test an overall validity of the model, we calculated for each test
the DEMINFIX(T) – DEMINFIX and the DEMAXFIX(T) – DEMAXFIX.Figures
show that saccade direction take in consideration mainly fixations of last
1000ms (1s).
07/01/13 www.evalab.unisi.it 5

6. 07/01/13 www.evalab.unisi.it 6

7. Model
07/01/13 www.evalab.unisi.it 7

8. Human vs Machine
07/01/13 www.evalab.unisi.it 8

9. Conclusion
• We found significant differences among tasks
and a correlation between the efficiency (time
elapsed) to explore the task and the ability to
inhibit the BAF.
• The command constraint (goal-driven) which is
modulated by the image salience versus BAF.
• The selection mechanism that drives this
competition. Further works will be directed to
evaluate the relation between the BAF and the
inhibition of return.
07/01/13 www.evalab.unisi.it 9

10. Conclusion
• We found significant differences among tasks
and a correlation between the efficiency (time
elapsed) to explore the task and the ability to
inhibit the BAF.
• The command constraint (goal-driven) which is
modulated by the image salience versus BAF.
• The selection mechanism that drives this
competition. Further works will be directed to
evaluate the relation between the BAF and the
inhibition of return.
07/01/13 www.evalab.unisi.it 9