Psychology2016

338 CHAPTER 8

Another problem is the number of celebrities who have joined the antivaccination move-

ment. These people have no real expertise, but they do have the ability to reach a lot of

people and—unfortunately—some people are very willing to believe their favorite celebrity

despite the lack of any authority on the subject at hand. The third criterion is one that is often

forgotten: just because someone is considered to be an authority or to have a lot of expertise

does not make everything that person claims automatically true, as the Wakefield disaster

clearly demonstrated. The evidence is what is important, and in the case of immunizations,

the evidence is clear: Vaccinate your children.

Adolescence

the period of life from about age
13 to the early 20s, during which a
young person is no longer physically
a child but is not yet an independent,
self-supporting adult.

puberty
the physical changes that occur in the
body as sexual development reaches
its peak.

Adolescence

Adolescence is the period of life from about age 13 to the early 20s, during which a young

person is no longer physically a child but is not yet an independent, self-supporting adult.

Although in the past, adolescence was always defined as the “teens,” from ages 13 to 19,

adolescence isn’t necessarily determined by chronological age. It also concerns how a per-

son deals with life issues such as work, family, and relationships. So although there is a

clear age of onset, the end of adolescence may come earlier or later for different individuals.

Physical Development

8.9 Describe the physical changes of puberty.

Isn’t adolescence just the physical changes that happen to your body?

The clearest sign of the beginning of adolescence is the onset of puberty, the physical

changes in both primary sex characteristics (growth of the actual sex organs such as the penis

Herd immunity is a term that refers to the immunity of a population to a particular disease, typically

because a majority of the population’s members have acquired immunity through vaccination. As

you can see from the diagram at the top, when a population does not have herd immunity, a disease

carried by only a few people, or even one person, can spread throughout the whole population. This is

what happened in the famous case of “Typhoid Mary,” in which a woman who carried typhoid spread

the disease to a large number of employers and their families. As more of a population gets immunized

(middle diagram), the spread of disease begins to lessen. As most of the population gets immunized

(bottom diagram), the spread of the disease is minimized—the “herd” is immune.

APA Goal 2 The Facts About Immunizations

interactive

?

= not immunized but still healthy = immunized and healthy

No one is immunized.

Contagious disease spreads

through the population.

= not immunized, sick, and contagious

Some of the population gets

immunized.

Contagious disease spreads through

some of the population.

Most of the population gets

immunized.

Spread of contagious disease

is contained.