Encyclopedia of Environmental Science and Engineering, Volume I and II

(Ben Green) #1

PSYCHOLOGICAL ASPECTS OF MAN’S ENVIRONMENT 1033


nitrogen dioxide can cause fatal poisoning at concentrations
which are not physically annoying.
Other Chemical Pollutants The behavioral effects of a
number of other chemical substances which may be of environ-
mental significance have been studied. These include alcohols,
various psychoactive drugs, and various industrial chemicals.
Ethyl alcohol has been found to increase reaction time by about
10% when the level of alcohol in the blood reaches 0.35%.
Blood alcohol levels of 100 mg/100 ml have been reported to
affect monitoring and tracking tasks, and lower levels have
been reported to affect various complex tasks.
It has been possible to study the effects of a number of
such chemicals in conditioning experiments. Several drugs
have been shown to increase eating or drinking behavior in
animals; these are usually drugs which act to reduce anxiety.
Meprobamate and similar drugs usually increase eating; the
barbiturates chiefly affect drinking. A number of such drugs
have been shown to produce decrements in escape or avoid-
ance conditioning, an effect usually attributed to their fear
or anxiety reducing properties. Morphine addiction can be
induced in animals, and the drug can serve as a positive rein-
forcer for behavior, permitting the study of various aspects
of addiction, such as withdrawal, in animals, using condi-
tioning concepts and procedures.
Depressant drugs, such as the barbiturates, have gener-
ally been found to impair memory in humans. Retrograde
amnesia (failure to recall events just before administration
of a drug or some traumatic incident, such as a blow to the
head) has been reported for ether and for CO 2 , administered
post-trial. However, conflicting evidence exists. Post-trial
administration of ether can also facilitate retention, and 30%
nitrous oxide has also been reported to facilitate retention in
humans when given after learning, though other studies have
found impairment with nitrous oxide.
Facilitation effects on memory have been reported for a
number of other drugs. Strychnine has been shown to improve
maze learning for food rewards, discrimination learning, and
other tasks. Various other substances have also been studied.
However, the results are conflicting at present.
The various effects of chemicals on retention have been
interpreted in various ways. It has been hypothesized that a
certain period of time is necessary following learning for con-
solidation of the memory trace. Drugs or other events, such as
a blow on the head, or the administration of electroconvulsive
shock, may interfere with this process and prevent the reten-
tion of learned responses over time. Other possible explana-
tions lie in facilitation or interference with nerve transmission
or with protein synthesis. The inhibiting effects of puromy-
cin and other antibiotics on some learned responses has been
attributed to their interference with protein synthesis, though
other explanations are possible. Explanations in terms of the
drug effects on the animals’ perception of the cues in the
learning situation have also been suggested.

Environmental Stressors

Unusual conditions of temperature, noise, lighting, vibration,
etc. may be encountered in some environments. Extreme values

of such stimuli are often regarded as environmental stressors,
and their physiological effects have been extensively studied.
Concern has also been felt about their behavioral effects, and
a number of studies have been done on this question.
Noise Excessive noise levels are known to be capable
of damaging the auditory system. Noise can also be annoy-
ing, and its annoying properties are a complex function of
its spectral composition (see Noise). It can also seriously
interfere with tasks which depend on auditory communica-
tion. However, studies of effects on non-verbal tasks have
reported mixed results, often negative. While interference
through distraction may occur with sudden unpredictable
sounds, in general, noise seems to have a minimal effect on
most non-verbal tasks. It should be kept in mind, however,
that adapting to noisy environments may impose additional
stress on the organism. Noise can induce audiogenic seizures
in susceptible strains of rats, and there have been reports of
sound-induced seizures in epileptics.
Temperature A number of studies have shown decre-
mental effects of elevated temperatures on a variety of tasks.
Telegraph operators who had been acclimatized to a hot envi-
ronment (Singapore) were studied at several temperatures
above that of their usual environment. Errors were found
that were related logarithmically to the temperature increase
in the receipt of coded messages made up of assorted letter
and number strings. Similar results have been reported by
artificially acclimatized subjects in England. Subjects’ judg-
ments of comfort are not necessarily reliable guides to the
temperature which gave best task performance. In general,
the relationship between behavior decrement and heat stress
is more straightforward for tasks involving physical effort
than for other tasks, but effects on both have been reported.
Cold has also been studied, chiefly in relation to its
effects on manual dexterity, which it decreases. Adaptation
effects are also reported to cold.
Studies have been reported which show decrements
in learning and retention with elevated temperatures, and
improvements with cold environments. The latter have
mostly been reported with invertebrates, and it is unclear
whether the effect is directly temperature related, or due to
restriction of activity with cold.
Vibration Excessive vibration has been shown to be
physically damaging, especially to the circulatory system,
in addition to causing symptoms such as seasickness in
susceptible individuals. In terms of effects on other behav-
iors, the chief effect has been shown on visual acuity; most
other studies have reported other behaviors to be unaffected.
However, vibration has been reported to be unpleasant, if
prolonged, even though the levels are below those believed
to cause physiological damage, and secondary effects might
be expected on monotonous tasks. The vibrations studied
have varied from 0–60 Hz, these being the range of practical
interest for most environmental purposes. Interactions with
frequency are known to exist. Frequencies in the range of
10–24 Hz most severely impair visual acuity, while manual
tracking is most seriously affected at frequencies of about
5 Hz. This frequency also produces the greatest subjective
discomfort.

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