Information Technology Reference
In-Depth Information
Arousal potential is a property of stimulus patterns and a measure of the ca-
pability of that stimulus to arouse the nervous system. Arousal potential has three
sources. First, there are
psychophysical
properties such as very bright light, very
loud sounds, sensations with an abrupt onset, very low or high frequency sounds,
and so on. Second, there are
ecological
stimuli such as survival threats like pain or
predator sightings, or cues associated with the availability of food. But the third and
strongest according to Berlyne are referred to as
collative
effects. These are com-
bined and comparative experiences that present arousal potential in a context depen-
dent and relative manner. Examples include “novelty, surprisingness, complexity,
ambiguity, and puzzlingness.” Berlyne (
1971
) explicitly notes the correspondence
between many of these collative effects and concepts from Shannon's information
theory.
The hedonic response to sources of arousal potential refers to the spectrum of
pleasure and pain we experience. Berlyne proposes that the hedonic response is the
result of separate and distinct reward and aversion systems. Each of these systems is
made up of neurones. The firing thresholds of individual neurones will vary accord-
ingtothe
normal
or
Gaussian probability
distribution as is typical in nature (see
Fig.
10.2
). Therefore the strength of the arousal potential will determine the number
of neurones that fire in response. The number of neurones responding will increase
as a
Gaussian cumulative distribution
, i.e. the area under the Gaussian probability
distribution as the threshold moves from left to right. Berlyne further proposes that
the reward system requires less arousal potential exposure to activate, but that when
activated the aversion system will produce a larger response.
The result is the hedonic response as a summation of the positive reward system
and the negative aversion system. With no arousal potential there is a hedonic re-
sponse of indifference. As more arousal potential is presented the hedonic response
increases manifesting itself as a pleasurable experience. Beyond a certain point,
however, two things happen. First, the reward system reaches maximum activation
and plateaus. Second, the aversion system begins to activate. As the aversion system
reaches higher levels of activation the hedonic response will lessen and eventually
cross into increasing levels of pain.
Berlyne notes that this function is usually called
the Wundt curve
, as it was first
presented by the “father of experimental psychology” Wilhelm Wundt in 1874. But
in Wundt's model the
x
-axis represents low-level neural intensity. Berlyne's arousal
potential on the
x
-axis includes psychophysical intensity, but it also includes ecolog-
ical stimuli and most importantly collative effects. For Berlyne increasing collative
effects such as novelty and surprise also represent increasing complexity in the in-
formation theory sense. From this point of view works of only moderate information
complexity maximise the hedonic response. This resonates well with the intuitive
artistic notion that audiences respond best to works that are not so static as to be
boring, and yet also operate within learned conventions so as to not be experienced
as chaotic.
There is, however, another interpretation. The notion of Gell-Mann's effective
complexity was previously mentioned. From that point of view complexity is a
balance of order and disorder, and biological life presents complexity at its peak.
