Psychology Lecture 20 (chapter 5)
Limon- you want to know at what point the stimulus’s energy can be received by the sensory system.
Difficult to measure.
Slide 17: first empirical psychology study in North America by Pearson Jastrow. Studied subliminal
messages and measure the threshold. Are there singular or multiple entrances for the information to get
You shuffle a deck of card, walking backwards until the patient can’t see what’s on the card anymore.
The experimenter shuffles the cards, and shows them one by one and asks the patient to say whether
they saw the letters and numbers. They had a good probability of guessing right, more than the chance,
meaning there are more than just the primary waking self. Info is getting in, and another entity seems to
also process it.
What’s the point of walking backwards? Related to the noticeable difference, and how much more
powerful does something else need to be to make it hard to see? How much stimulus is needed for you
to recognize something from zero? Jastrow uses the reverse of the last question.
However, this experiment relies on the patient’s response. This has a demand characteristic, which
affects the way you interpret the role (ex. What do you mean you can’t see? Nothing? Just a white card?
Or the letter shouldn’t be visible?). The experiment can cause a bias, with a pressure for the patient to
respond they can’t see.
Some people are more liberal and others more conservative.
Perceptual defense, by Freudian theory; there’s the intention to keep your consciousness pure. Ex. If
you show words briefly (Slide 20). If you present negative words (like swearing), people tend to take
longer to look at the picture until they say it. That’s because the perceptual defense holds them back of
taking them in. Maybe the patients were surprised, and each person would take a variety of words (ex. A
female wouldn’t read off penis in front of a male experimenter because she’s more self-concious about
it. Some patients read it faster though response BIAS).
Slide 22: Signal detection theory. You ask the person to state or guess the stimulus. Trial- hit, the patient
sees the stimulus. Miss- the patient doesn’t see the stimulus even though there is one. If you don’t
present a stimulus but the patient still says they say see one, then it’s a false alarm. This can occur when
it’s difficult to distinguish the presence and absence of a stimulus.
Slide 23: each card is a trial, and each trial can have a word or not. Each is shown to you and you say if
there something or nothing shown. These are superliminal because everyone can see the words.
Slide 25: A casual person who doesn’t care about false alarms are more likely to state his and false
alarms, while more cautious people have a lower rate. There is still a bias, but a technique called optimal
sensitivity in respect to bias is used to measure the bias.