remains controversial. Other researchers have found
no such link, or have noted small and largely mean-
ingless effects. When increases in achievement are
found, however, they tend to be centered on the early
primary grades and students who are disabled or
high-risk. In one example, Project STAR (Student-
Teacher Achievement Ratio) in Tennessee, students
were randomly assigned to either large or small class-
es during the early primary grades. It was found that
students from smaller classes reported higher
achievement, which persisted through seventh grade.
Increased achievement is attributed to the teacher’s
increased ability to respond to students, fewer class-
room discipline problems, and reduced likelihood of
teacher burnout. Teachers universally report their be-
lief that they teach more effectively and with less frus-
tration in smaller classrooms, although sometimes
this is not supported by independent observations. It
appears that some training for teachers in how to
make the most of smaller class sizes is beneficial.
See also: HOME SCHOOLING; SCHOOL VOUCHERS
Bibliography
Achilles, Charles. ‘‘Students Achieve More in Smaller Classes.’’ Ed-
ucational Leadership 53, no. 5 (1996):76–77.
Bennett, Neville. ‘‘Annotations: Class Size and the Quality of Edu-
cational Outcomes.’’ Journal of Child Psychology and Psychiatry
39, no. 6 (1998):797–804.
Susan L. O’Donnell
CLASSICAL CONDITIONING
Classical conditioning is a basic behavioral process in
which stimuli come to evoke responses: When an ob-
ject or event (such as food) that already evokes a be-
havior (such as salivation) is associated with one that
does not (such as a bell), the latter may evoke a reac-
tion similar to that of the first object or event. When
the stimuli are no longer associated, the conditioning
weakens (called extinction); when stimuli resemble
the conditioned stimulus, they evoke similar reactions
(called generalization). First systematically studied by
Ivan P. Pavlov (1849–1936), classical conditioning be-
came a model for all behavioral development. B. F.
Skinner’s (1904–1990) research, for a while, on the
conditioning of voluntary (operant) behavior through
reinforcement restricted its scope. Classical condi-
tioning occurs only in the involuntary (respondent)
behavior of reflexes, glands, and internal organs
(e.g., orienting reactions, intestinal functions, insulin
secretion, heart rate), especially as they participate in
emotional behavior (e.g., anxiety, elation). Today,
classical conditioning and extinction are widely used
in the treatment of emotional disorders (e.g., pho-
bias) and the side-effects of medical treatments (e.g.,
nausea caused by chemotherapy).
See also: LEARNING; SKINNER, B. F.Bibliography
Catania, A. Charles. Learning, 4th edition. Upper Saddle River, NJ:
Prentice-Hall, 1998.
Kehoe, E. J., and M. Macrae. ‘‘Classical Conditioning.’’ In William
O’Donohue ed., Learning and Behavior Therapy. Boston: Allyn
and Bacon, 1998.
Rescorla, R. A. ‘‘Pavlovian Conditioning: It’s Not What You Think
It Is.’’ American Psychologist 43 (1988):151–160.
Edward K. MorrisCLEFT LIP/CLEFT PALATE
A cleft lip is a birth defect that occurs when the lip and
the front part of the dental arch fail to form and fuse
correctly. Cleft palate is the failure of the back part of
the hard or soft palate to form. Approximately 1 in
800 newborns has a cleft lip or palate. Every day in
the United States, fourteen babies are born with cleft
lip (with or without cleft palate) and seven babies are
born with cleft palate alone. There are 150 U.S. and
Canadian interdisciplinary cleft and craniofacial
teams that help coordinate care with multiple health
professionals (including medical, surgical, dental,
orthodontic, speech pathology, and psychosocial
workers). Issues faced by families may include feeding
difficulties, speech and articulation problems, dental
development, ear infections and hearing concerns,
teasing and stigmatization, multiple surgical treat-
ments, and sometimes learning problems. Treatment
results are generally excellent and most children born
with cleft lip and/or palate grow up to be well-adjusted
and successful adults.See also: BIRTH DEFECTSBibliography
Bzoch, Kenneth R. Communicative Disorders Related to Cleft Lip and
Palate, 4th edition. Austin, TX: Pro-Ed, 1997.
‘‘Oral Health in America—Executive Summary: A Report of the
Surgeon General.’’ In the U.S. Department of Health and
Human Services, U.S. Public Health Service [web site]. Wash-
ington, DC, 2000. Available from http://www.nidcr.nih.gov/
sgr/execsumm.htm; INTERNET.
Strauss, Ronald P. ‘‘The Organization and Delivery of Craniofacial
Health Services: The State of the Art.’’ Cleft Palate-Craniofacial
Journal 36, no. 3 (1999):189–195.
Ronald P. StraussCLIQUES
The term cliques refers to clusters of children and ad-
olescents whose mutual friendships form a cohesive
network. By middle childhood, clique boundaries can
be defined by identifying groups of children who all86 CLASSICAL CONDITIONING