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Intention Generator

Fig. gif illustrates a simplified generic intention generator which is responsible for the goal-directed behavior of the artificial fish in its dynamic world.

  figure1418

The intention generator is based on a priority hierarchy of behaviors. Life threatening behaviors, such as collision avoidance, have highest priority. As indicated in the figure, the intention generator first checks the sensory information stream to see if there is any immediate danger of collision. If there is (see Chapter gif for collision test) then the intention I generated is to avoid collision. If there is no immediate danger of collision, the neighborhood is searched for predators, the fear state variable F and the most dangerous predator m for which tex2html_wrap_inline3544 (for any predator i) are calculated. If the total fear tex2html_wrap_inline3548 (where tex2html_wrap_inline3550 is a threshold value) evasive action is to be taken. If the most dangerous predator is not too threatening (i.e. tex2html_wrap_inline3552 where tex2html_wrap_inline3554 ) and the fish has a schooling habit, then the school intention is generated, otherwise the escape intention is generated.

If fear is below threshold and the behavior memory (more details are in Section gif below) is empty, the hunger and libido mental state variables H and L are calculated. If the greater of the two exceeds a threshold 0 ;SPMlt; r ;SPMlt; 0.5, the intention generated will be to eat or mate accordingly. If H=L;SPMgt;r, then tex2html_wrap_inline3564 is checked to see if it is one of the two intentions eat and mate. If not, one of them gets chosen at random, otherwise tex2html_wrap_inline3566 .

If the above test fails, the intention generator accesses the ambient light and temperature information from the perception system. If the fish's habits imply contentment with the ambient conditions, the intention generated will be to wander about, otherwise it will be to leave the vicinity. Note that, unlike the desire to eat, to mate or to escape which are modeled explicitly by the mental state variables, the desire to avoid collision, to school, to wander and to leave are modeled implicitly by their intrinsic behavioral priorities (level in the hierarchy), sensory stimuli and innate habits. The following diagram shows all the desires ordered according to their levels in the priority hierarchy:

Desire to avoid collision
tex2html_wrap_inline3568
Desire to flee from predator
tex2html_wrap_inline3568
Desire to eat, Desire to mate
tex2html_wrap_inline3568
Desire to school
tex2html_wrap_inline3568
Desire to wander, Desire to leave


next up previous contents
Next: Why Hierarchy? Up: The Behavior System Previous: Satiation of a Desire
Xiaoyuan TuJanuary 1996