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of the diaphragm is to create an air pressure differential inside the thoracic cavity so
that the air can move in and out.
Structures are necessarily involved in the execution of behaviors that leads to
particular functions. In complex systems, several structures might be involved in
the same function. For example, the diaphragm, intercostal muscles, and ribs are all
coordinated in the function of moving air into and out of the body. Similarly, the
behavior of one particular structure often affects the behavior of other structures.
For example, the blood vessels transport oxygen and nutrients throughout the body.
However for this behavior to occur, the heart must pump the blood through the
vessels.
The SBF representation also accounts for the expert-novice differences in com-
plex systems domains (Hmelo-Silver & Pfeffer, 2004; Hmelo-Silver, Marathe, &
Liu, 2007). Using clinical interviews, Hmelo-Silver and colleagues (2007) studied
expertise in two complex systems domains: the human respiratory system and the
aquarium systems. They found that novices tended to think about isolated structures
whereas experts integrated behavioral and functional perspectives when asked to
describe their understanding about these systems. For example, novices only talked
about the surface components of the respiratory system, such as lungs, airway, ribs,
and seldom mentioned the deep underlying mechanisms, such as how oxygen gets
into the body or how diffusion occurs in the lungs. In comparison, experts explained
about the underlying mechanisms, such as how the cellular respiration and the dif-
fusion happen, which actually connected most of the components within the system.
Furthermore, novices rarely mentioned those nonsalient elements that are either
invisible or involved in complex causal mechanisms, such as the cellular respira-
tion. In other research, Egan and Schwartz (1979) found that the functional aspect
of conceptual representation might contribute to the distinctions between expert and
novice understanding. They asked expert and novice electronic technicians to recon-
struct symbolic drawings of circuit diagrams. They found that skilled technicians
replicated the drawings based on the functional nature of the elements in the cir-
cuit (e.g., amplifiers, rectifiers, and filters). In contrast, novice technicians replicated
drawing based more on the spatial proximity of the presented elements. Both studies
suggest that a functional understanding is a characteristic of experts, consistent with
Hmelo-Silver et al. (2007).
If functional understanding is characteristic of experts and a key form of domain
reasoning in life sciences, then it also suggests that an emphasis on function and
helping learners make connections across different SBF levels might be used to
create instruction that will lead to a deep understanding. Liu, Hmelo-Silver, and
Marathe (2005a) compared the effects of two alternative versions of hypermedia
on the development of conceptual understanding of the human respiratory system.
The function-oriented version emphasizes the “how” and “why” of the system and
is consistent with both expert understanding and canonical biological explanations.
The structure-oriented hypermedia emphasizes the “what” of the system, similar to
most textbooks. The findings showed that the function-centered hypermedia helped
students gain a deeper understanding of the system than the structure-oriented
version. Moreover, the function-oriented version helped students learn about the
