An Experimental Study

SENSATION & PERCEPTION

GOALSReview an experimental study on

sensation and perception

Apply our knowledge of research to critically exam the study

Develop our own hypotheses for future research

Sensation vs. Perception• Sensation: When energy is detected by

receptors on our sensory organs and transformed into neural energy (Transduction)

• Perception: The process of organizing and interpreting sensory information so that it makes sense

PERCEPTIONOccurs in the brain

&

is influenced by our Perceptual Sets (Experience & Expectations)

as well as by Context, Emotions, & Motivation

Signal Detection Theory• Signal Detection Theory predicts when we will

detect weak signals (“hits” to “false alarms” ratios) in order to try and understand:– Why people respond differently to the same

stimulus and– Why the same person’s reactions vary in differing

circumstances

• Reliability = Does it provide a consistent result (even if it is wrong)

• Validity = Does it measure what it says it measures (Does the steak cause a difference in the weight shown on the scale?)

• Generalizability (External Validity) = Can we generalize the results of our study to other situations and people

Is it Really a Very Good Study?

Emotion Guided Threat Detection: Expecting Guns Where There Are None

• Like most quantitative researchers, Jolie Baumann and David DeSteno (2010) wanted to conduct and publish a good experimental study.– Specifically, they hypothesized that emotion (e.g.,

anger as the IV) causes people to perceive an object as a gun even if it is not a gun

Expecting guns where there are none:Sensation and emotion affect perception

Perception:The object is a

gun!…or not.

Stimulus:Object in a man’s hand

Sensation - Eyes:Light Waves, Color, Forms

Emotion:Angry, happy, or neutral

Action:Press Z key on keyboard if gun or press / key if not gun

Accurate Not accurate

Sample• 84 undergraduates (49 Women, 35 Men)

in partial fulfillment of a course requirement, were randomly assigned to one of three groups (Neutral, Angry, Happy)

Procedures

Hand-Eye CoordinationPractice Test

Memory Task Emotion Induction IV

Hand-Eye CoordinationManipulated DV

A Short QuestionnaireManipulation Check

The numbers were crunched & the hypothesis was supported: Angry people are more likely, than happy or neutral people, to identify an object as a gun when it is not, but….

• How do we, as critical thinkers, determine whether:– The measures used in the study are reliable?– The statements about causality are valid? Does it

measure what it says it measures?– The results/findings are generalizable?

How do we know whether Baumann & DeSteno used…

• Reliable measurements?– Emotion induction• It was a uni- or one-dimensional task [participants had to

write one type of event – neutral, happy, angry] and it’s easier to interpret one-dimensional tasks.

– “Threat detection” / “Perception Measure”• Video game, in its computerized presentation of images

for a pre-specified amount of time (750 ms) on a computer screen, was stable as well as used repeatedly across several studies since 2002.– Computers, with their fancy calculations, are generally unbiased,

accurate, precise, and reliable.

• However I do want to point out that this one was “adapted”…

Adaption #1

Aggressive

Action Tenden

cies

Emotion

Changed shooting people who are believed to have guns to clicking a button to identify if the person is believed to be holding a gun

There will be an increase in

perceptions of threat for any generic social

target

When Stereotypes & group prejudices

are removed

“Those not associatewith stereotypes indicative of violence”So we will only use

White Men as targets

Adaption #2

Given all of that…

Is this a Reliable measure?

How do we know whether thestatements of causality are valid?

• Where was the experiment conducted?• We know that experiments conducted in laboratory settings -

where there is more experimenter control of the setting and independent variables are manipulated - have higher internal validity.– Internal validity is about causal control (cause-effect)– This study WAS conducted in a lab setting

• How were people put into groups? • Random assignment to groups– Rules out many threats to internal validity

• Order of measures- Manipulation of emotion 1st, then computer task

A closer look at internal validity

• The degree of certainty with which statements can be made about relationships

• How certain are you about the statements:– Emotion affects our perception of objects.– Anger causes people to perceive an object as a

gun even if it is not a gun.• What conditions might affect our level of

certainty?

• Internal validity– The degree to which causality can be inferred

from a study• Is the independent variable producing the changes in

the dependent variable?• Anger (IV) [influences perceptual categorization and]

causes people to misidentify (DV) neutral objects as guns

Indications that Baumann & DeStento’s findings are valid

• Random assignment of participants to groups– Writing about an angry event; writing about a happy event;

writing about a normal day (control)• Participants thought the experiment was about memory,

not perception • Two checks regarding specific emotions:

– Emotion apparent in written piece (checked by one researcher)– Participants self-reported on a 7-point scale questionnaire

about how they were feeling to see if the writing task caused participants to select related feelings of anger, happiness, etc.

– All tasks corresponded within groups AND significantly differed from the emotions reported in other groups

Indications that Baumann & DeStento’s findings are valid

• The outcome variable (accuracy calculation of object identification) was assessed after the experimental task.– The order is important. Emotion manipulation

first, then the computerized task of object identification makes the statement “emotion affects perception of object” more valid.

Generalizability (aka External Validity)

• You tell me, are the results generalizable to a larger population?• It is difficult to say to whom the result could be generalized to

since we don’t have the demographics of the sample used• The results were transferable to later studies, which counts for something in

the research world • It was a sample of convenience…in fact, it was, in part, a course requirement to

participate in research study• Common practice, but might it affect results? Ideally, researchers need a sample of a

given population where participants are chosen by chance

• Can the results be generalized into an interaction on State St.• No, but they can support a concept and build a foundation for future studies to

explore this further

So what do you think?• What does our critical examination of the

research mean?

• How does this study make you feel?• What did it make you think?• What do you want to know? • What are your hypotheses?

Really Very Good

Research as a tool for Social Justice

ReferencesBaumann, J. & DeSteno, D. (2010). Emotion guided threat detection: Expecting guns where there are none. Journal of

Personality and Social Psychology, 99 (4), 595-610.Myers, D. (2014). Exploring psychology in modules (9th ed.). New York, Worth Publishers.Sanders, L. D. ((2010). Discovering research method in psychology. West Sussex, BPS Blackwell.

Verdugo, E. (1998). Practical problems in research methods: A casebook with questions for discussion. Los Angeles, Pyrczak Publishing

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Happy http://powertochange.com/wp-content/uploads/2011/01/happyperson.jpg

Angry baby http://powertochange.com/wp-content/uploads/2011/01/happyperson.jpgNeutal face http://dericbownds.net/uploaded_images/w_unsexy.jpgChess Pieces http://mesosyn.com/mental8-8q.jpg