- Registration time
- Last login
- Online time
- 0 Hour
- Reading permission
Learning and Fear
The fear system in humans and animals provides a good illustration of the
intertwining of domain-specific with domain-general learning mechanisms. Cer-
tain stimuli recurrently associated with danger in the EEA are particularly easy to
acquire and difficult to extinguish (e.g., Öhman & Mineka, 2001; Seligman, 1971).
The fear system is therefore selective in its inputs because some stimuli more eas-
ily induce fears: “Evolutionary contingencies moderate the ease with which par-
ticular stimuli may gain control of the module” (Öhman & Mineka, p. 488).
However, other stimuli can gain control of the fear system. The adaptive-
ness of domain-general aspects of the fear system can be seen from data show-
ing that when the UCS is highly aversive or when a CS without any evolution-
ary significance is known to be very dangerous, the differences between evolutionarily primed fears and nonevolutionarily primed fears disappear. Thus, pointed guns are a very potent stimulus for fear in our culture saturated with media reports and dramatizations of shootings, with the result that guns activate
the fear system in a manner indistinguishable from evolutionarily prepared stim-
uli like snakes and spiders. Hugdahl and Johnsen (1989) found the stimulus of
a gun pointed at the participant followed by a loud noise showed superior con-
ditioning compared with slides of snakes. Moreover, the CS of the gun pointed
at the participant was nearly identical in extinction rate to a snake pointed at the
participant when both were followed by a shock. The results indicated that pro-
longed experience with stimuli such as pointed guns associated with intensely
aversive outcomes eventually leads to enhanced connections in the amygdala
that “function like evolutionarily prepared associations” (Öhman & Mineka,
2001, p. 513). Similarly, Sutton and Mineka (as cited in Öhman & Mineka) did
not find a covariation bias for images of a knife-wielding male dressed in black
under normal, nontraumatic conditions but did find a covariation bias similar to
that for evolutionarily prepared stimuli among students primed by real-life
reports of local knife-wielding criminals and a stabbing on campus.
In this case, fear of a person wielding an item that was not an evolutionary danger produced
the sort of bias typically found with evolved fears. Similarly, Lautch (1971)
found that intense trauma could result in phobias even toward normally benign
objects with no evolutionary prepotency.
Domain generality is also implied by data indicating there are two different
learning systems relevant to fear in animals and humans (LeDoux, 1996; Öhman
& Mineka, 2001). The inputs to the amygdala fear system include prepared con-
nections between fear responses and evolutionarily recurrent stimulation,
although, as we have seen, nonprepared stimuli also have access to the system.
The domain-general associative learning system in the hippocampus is activated
in attempts to link any and all available stimuli to aversive UCSs, including a
range of contextual stimuli. Öhman and Mineka suggest this system typically
functions in novel and unnatural situations typical of laboratory studies on ani-
mals in which the aversive UCS is very motivating and in which picking up any
and all available information on cues related to the appearance of the UCS may
be vital. With humans, Campbell, Sanderson, and Laverty (1964) found a long-
lasting conditioned fear response to an arbitrary tone CS following a single trau-
matic event involving the suspension of breathing because of a drug injection.
There was no extinction even at a follow-up 3 weeks after the experiment. The
drug did not cause pain, but the experience was described by participants as
“extremely harrowing” (p. 632).
In conclusion, the fear system fails to qualify as a module because stimuli
with no phylogenetic importance can serve as CSs for activating the system, espe-
cially if they are intensely aversive. Domain-general learning mechanisms of clas-
sical conditioning function both in mildly aversive situations without the involve-
ment of the amygdala fear system and in intensely aversive situations with involvement of the amygdala fear system, where any and all available informa-
tion on contingency is of critical adaptive importance. Nor is the system encap-
sulated, because domain-general cognitive mechanisms are able to influence the
effectiveness of UCSs in producing fear CRs. Experience with dangerous objects
also influences expectations that such objects will have aversive effects and
results in stronger fear CRs that are more resistant to extinction.