Page 247 - Deep Learning

230 Adaptation

the cumulative results of multiple learning events. In this sense, the model
shows that the learning mechanism is sufficient to acquire ecologically valid
skills through practice. The three skills are very different in character, which
provides modest confidence in the robustness and content-independence of
the learning mechanism. Besides providing snapshots of constraint-based
learning in ecologically real task domains, the three applications provide
novel perspectives on transfer of training and the nature of instruction, thus
answering the fifth and sixth questions about practice posed in Chapter 6.
In science education, students often acquire problem-solving skills in two
steps. First, the student studies the relevant theory, its concepts and prin-
ciples, presented in a declarative format. Second, the student attacks some
class of problems for which the theory specifies correct solutions, and the
student practices until he has mastered a relatively well-defined strategy for
this class of problems. Textbook chapters often implement this two-punch
scenario.
To simulate this scenario, HS learned to construct Lewis structures, a rou-
tine problem-solving skill in high school and college chemistry. Chemists use
several different symbolisms for representing atoms and molecules. The most
basic is the sum formula, which states how many atoms of each type a mole-
cule contains. For example, the sum formula for ethanol (commonly known as
ethyl alcohol or just alcohol) is C H OH, indicating that 1 molecule of ethanol
5
2
contains 2 carbon atoms, 1 oxygen atom and 6 hydrogen atoms. Sometimes
chemists need to know which atom is connected to which other atom. This is
represented in a structural formula, also called a Lewis structure. The struc-
tural formula for ethanol is shown in Figure 7.3.
To construct a Lewis structure is to derive the correct structural formula,
given the sum formula. The Lewis structure for a molecule is constrained by
the theory of the co-valent bond, the type of chemical bond symbolized by the
35
horizontal and vertical lines. Basic principles of this theory include that each
bond requires the sharing of 2 electrons; that only the valence electrons, the
electrons in the outermost electron shell, can participate in such bonds; that

Figure 7.3. The structural formula for ethanol
(C 2 H 5 OH) as it might be presented in a college
textbook. Each line between two atoms stands for
a shared pair of electrons.