psychophysics Connects psyche (psycho) to body (physics) threshold = cutoff point, something different happens above point than below point

Threshold for detecting light How much light is necessary for you to detect that there is light? Stimulus above threshold (e.g., room lights) is called “supraliminal” (supra = above; liminal = threshold) stimulus below threshold (e.g., light too weak to see) is called “subliminal”

Mind/body connection If we measure threshold, then we show a relationship between a physical stimulus and your psyche (in other words, psychophysical relationship)

Sample psychophysical study Having various stimuli (in this case, light), of different strengths weak stimuli (low light) and medium stimuli and strong stimuli (strong lights) sometimes, cases with no light (no stimulus) participant’s response: yes or no, can they see a light?

Low vs. high threshold Low threshold = good at detecting light, so would say “yes” to weak stimulus high threshold = bad at detecting light, so would say “no” to a weak stimulus

Graphical representation of threshold Threshold = point at which S detects stimulus 50% of the time threshold Supra- liminal Sub- liminal % detection Signal strength

How to interpret threshold? Threshold is a measure of your awareness of a stimulus, or a measure of your consciousness of a stimulus threshold is dividing line between unconscious and conscious below threshold = unconscious above threshold = conscious

perception Making sense of a stimulus e.g., knowing that the room lights are turned on when they are turned on e.g., FRIED -> perceived to be the word “fried” applies to all senses

Perception Aka, identification, recognition, pattern recognition “percept” = the idea of what the stimulus is = conscious experience of a stimulus unconscious perception = processing or identifying a subliminal stimulus

Measuring perception Perception is very rapid (usually less than a second) typically, use a computer and measure reaction time show two objects, either same or different, and person responds “same” or “different” by pressing one of two different keys

Measuring perception (cont.) RT measures how long it takes to decide if the objects are the same or different but also first must perceive the objects before you can compare them also measures time it takes to remember which key to press

Choice RT Choice RT = having to decide between two or more options and having to decide between two or more responses (which key to press) e.g., choice is between “same” or “different”

Paper-and-pencil version Give a whole set of pairs of letters on a sheet of paper S marks answer -- same or different -- on sheet of paper next to each pair of letters measure RT from when they start on the first letter pair and finish with the last letter pair