Quick Definition
Subliminal is a two part word consisting of the
prefix sub- and the root word limen (Latin origins). Sub-
means below and limen means threshold. Thus, subliminal comes to mean
below threshold. But what is a threshold?
Thresholds
According to Schmeidler, and the vast majority
of psychologists studying subliminal phenomena, a threshold is the point
at which a stimulus is perceived 50% of the time. For example, to test
my aural threshold i would listen for presented stimuli at varying
volumes and frequencies. To signal that I heard the tone--I perceived
the stimulus--I would raise my hand or press a button, which ever the
researches had instructed me to do. By controlling and tracking the frequency
and volume of the emitted sound, the researchers are able to find the
point at which I hear a sound--perceive the stimulus--half of the time.
This point is my aural threshold. A working definition of threshold is
paramount. It acts as the scientific base for research in this area; a
foundation on which all data are defined. For some, this is where the
problems with subliminal research begin.
Visual Subliminal
Perception
A series of nothings become
something
When a person is flashed an image, the brain maintains a type of "footprint"
or "after image" of the stimulus. That is, despite the fact
that the stimulus was only presented for a fraction of a second, for a
short time that image is still seen by the brain. When first exposed the
subject may remember the shape of the beginning of a word. Then, as the
image continues to flash, the brain still "sees" the first shape
while adding an aditional footprint for the middle of the image. Continuing
in such a way, a subject can piece together these footprints--these "series
of nothings"--and form/recognize the word as a whole (Schmeidler
127).
How visual masking works
The masking of visual perception is generally the taking away of the "footprint"
created by the target stimulus. A nonsense image (a series of letters
that spell nothing, a line pattern, etc.) is flashed immediately after
the target image. This leaves the footprint of the nonsense image lingering
around as opposed to that of the target image (Epley
7).
Aural Subliminal Perception
Don't steal!!
Many department stores utilize subliminal messages to discourage theft.
They use audio messages masked in the "store's music" (many
stores play music over their intercom system). Masked audio messages are
generally compressed or accelerated to a degree that renders them unintelligible,
even if supraliminal. The message is then masked by the playing of, in
this case, music. This music is the primary channel--it is the easiest
to perceive. The hidden message becomes the secondary channel. (Moore)
This tactic may not be futile, "numerous findings indicate not only
analysis of secondary channel content at the level of individual words,
but short persistence of memory for that content" (Greenwald
5). Perceived or not, there is still the controversy over whether
or not it will influence one's behavior.
Difficulties with research
Troubles with thresholds
To begin with, psychologists have essentially massaged the theory of thresholds
so that subliminal perception could "exist in a form that can be
studied". In the1800's, Herbart and Fechner used the term limen as
a distinction between conscious and unconscious. Much of the research
conducted during the 1950's and on is based on a distinctive breaking
of "threshold" into two parts: sensory threshold and perceptual
threshold: stimuli that are "sensed by the body, but not conscious"
and stimuli that are "made conscious", respectively. It is the
perceptual threshold that is utilized in the realm of subliminal perception
research (Erdelyi 3). Thus, what the researchers
are studying are stimuli that are above the sensory threshold, but below
the perceptual threshold (the point at which a subject can perceive a
stimulus 50% of the time). This begs debate for it is sidestepping the
entire concept of a dichotomy between conscious and unconscious, the exact
concept of subliminal.
Already known from other areas of research is the fact that we do receive
information in our lower brain that never makes it to the cortex. The
cortex is where things are "made conscious". This is where sensory
perception comes in to play. It is estimated that for every 1,000,000
stimuli that pass by the sensory threshold, one stimulus passes through
the perceptual threshold (Norretrandesr 161).
This is how the intricacies of human behavior are explained. Humans simply
do too much to be conscious of it all. As McConnell points out, "We
are a walking mass of thresholds."
Each person has their own unique set of thresholds. To measure the threshold
of each subject prior to conducting the experiments is both time consuming
and redundant, but does account for such idiosyncrasies. However, not
only do thresholds vary from person to person, but they also vary day
by day within one individual. So what I can't hear today I may hear tomorrow
and vice versa (McConnell, Moore).
With no static threshold, or statistical foundation, research conducted
on subliminal perception today becomes invalid tomorrow.
Erdelyi (3) brings up an intriguing point. He asserts that these problems
with thresholds are not methodological hindrances, but rather they are
conceptual flaws. This reminds the community that indeed this research
is not truly "subliminal".
Attention
Attention plays a role on the research of subliminal perception. It is
capable of skewing results because the subject is instructed to listen
for a sound or to look for a sight. When trying to ascertain if one can
be influenced subliminally in day to day life, the person will not be
actively looking or listening for the supposed stimuli/message. To counter
this, study designs should keep the subject unaware of the target stimuli
(Shiffrin 55).
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