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== Applications to Human Behavior Recognition ==
[[Image:Kitchen.png|right|thumb|500px|
Figure 1. Layout for kitchen. (a) the “food preparation first” and (b) the “washing dishes first” meal preparation sequences. <br>
Image from <ref name="RecognitionOfHumanActivityThroughHierarchicalStochasticLearning" />]]
Hierarchical Hidden Markov Models (HHMMs) have been used in the context of eldercare aiming to identify behaviors such as eating dinner, watching television, and cooking <ref name="RecognitionOfHumanActivityThroughHierarchicalStochasticLearning" />. The goal is to learn the pattern of executing such activities normally, so that when an abnormal execution occurs (e.g., an elder person falls down while cooking), it can be automatically and instantaneously detected. Then, the appropriate action (e.g., provide audio/video cues to help the elderly or notify the appropriate caretaker that the elderly needs help) can then be taken before negative consequences for the elder person's health occur.
[[Supervised learning]] (a class of [[machine learning]] techniques) was used in <ref name="RecognitionOfHumanActivityThroughHierarchicalStochasticLearning" /> to learn an HHMM for four simplistic ways for dinner preparation ("spending some time preparing the food and rummaging through the fridge before the meal is cooked", "washing dishes prior to cooking on the stove", "going to the sink to wash the dishes then spending time at the food preparation area and the fridge before finally cooking the meal", "transition between each area of interest in a round robin fashion, starting and ending at the stove, before leaving the room") and five typical living room activities ("watch television", "read a book on the couch", "eat dinner", "eat dinner while watching television" and "there is nothing good on TV, read a book instead"). The person's position in the room was captured at short intervals of time and a sequence of observations was thus created. Observation sequences were labelled with the corresponding behavior and were used to learn HHMMs for the high-level dinner preparation and living room behaviors. Two example kitchen behaviors are shown in Figure 1. Figure 2 shows an HHMM learned for the "food preparation first" kitchen behavior.
[[Image:LearnedHHMM.png|right|thumb|700px|
Figure 2. Learned HHMM for "food preparation first" kitchen behavior. <br>
Image from <ref name="RecognitionOfHumanActivityThroughHierarchicalStochasticLearning" />]]
== References ==
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