Tuesday, August 19, 2008

GaCIT in Tampere, day 1.

The first day of the summer school on gaze, communication and interaction technology (GACIT, pronounced gaze-it) were started of by a talk with Boris Velichkovsky. The topic was visual cognition, eye movement and attention. These are some of the notes I made.

Some basic findings of the visual system were introduced. In general, the visual system is divided into two pathways, the dorsal and ventral system. The dorsal goes from the striate cortex (back of the brain) and upwards (towards the posterior parietal). This pathway of visual information concerns the spatial arrangement of objects in our environment. Hence, it is commonly termed the "where" pathway. The other visual pathway goes towards the temporal lobes (just above your ears) and concerns the shape and identification of specific objects, this is the "what" pathway. The ambient system responds early (0-250ms.) after which the focal system takes over.

These two systems are represented by the focal (what) and ambient (where) attention systems. The ambient system has a overall crude but fast response in lower luminance, the focal attention system works the opposite with fine, but slow, spatial resolution. Additional, the talk covered the cognitive models of attention such as Posner, Broadbent etc. (see attention on Wikipedia)

A great deal of the talk concerned the freezing effect (inhibition of saccades and a prolonged fixation) which can to some extent be predicted. The onset of a dangerous "event" can be seen before the acctual response (the prolonged fixation) Just before the fixation (500ms) the predicition can be made with a 95% success. The inhibition comes in two waves where the first one is issued by the affective repsonse of the amygdala (after 80 ms.) which acts on the superior colliculus to inihibit near saccades. A habituating effect on this affective response can be seen where the second wave of inhitition (+170ms.) becomes less apperent, the initial response is however unaffected.

While driving a car and talking on the phone the lack of attention leads to eye movements with shorter fixation durations. This gives an approximated spatial localization of objects. It is the combination of a) duration of the fixation and b) the surrounding saccades that determines the quality of recognition. A short fixation followed by a long subsequent saccade leads to low recognition results. A short fixation followed by a short saccade gives higher recognition scores. A long fixation followed by either short or long saccades leads to equally high recognition results.

Furthermore, a short saccade within the parafoveal region leads to a high level of neural activity (EEG) after 90ms. This differs from long saccades which gives no noticable variance in cortical activity (compared to the base line)

However, despite the classification into two major visual systems, the attentional system can be divided into 4-6 layers of organization. Hence there is no singel point of attention. They have developed during the evolution of the mind to support various cognitive demands.

For example, the role of emotional respones in social communication can be seen with the strong response to facial expressions. Studies have shown that male responds extremely fast to face-to-face images of other males expressing aggressive facial gestures. This low level response happens much faster that our conscious awareness (as low as 80ms. if I recall correctly) Additionally, the eyes are much faster than we can consciously comprehend, as we are not aware of all the eye movements our eyes perform.

In the afternoon Andrew Duchowski from Clemson University gave a talk about eye tracking and eye movement analysis. Various historical apparatus and techniques were introduced (such as infrared corneal reflection) Followed by a research methodology and guidelines for conducting research. A pratical example of a study conducted by Mr. Nalangula at Clemson was described. This compared expert vs. novices viewing of errornous circuit boards. Results indicate that the experts scanpath can improve the results of the novices (ie. detecting more errors) than those who received no training. A few guidelines on how to use visualization were shown (clusters, heatmaps etc.)

The day ended with a nice dinner and a traditional Finnish smoke-sauna followed by a swim in the lake. Thanks goes to Uni. Tampere UCIT group for my best sauna experience to this date.

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