Quiz 6 Flashcards
What is a discrimination experiment used for?
- To determine if 2 or more stimuli are perceived as the same or different
- no need to name or categorize the stimuli
Ex. AX, ABX, 2AFC - do not need to prepare—participants just identify whether there is a difference between 2 specific stimuli
- don’t need to know categories or name anything
What is an “identification” experiment?
- participants listen to one sound, need to categorize into a given category
- requires naming perceived stimuli based on predefined categories
Ex. Labeling tasks, Yes-No tasks
What are the 2 basic types of perception experiments
Discrimination or identification
What is AX design? What else is it known as?
- AKA Same-different design (a form of discrimination experiment design)
- ‘A’ refers to one sound, ‘X’ to another sound
- Use when curious about sensitivity to differences between sounds
- 2 stimuli presented at each trial
*common in speech research
What are the elements of an AX design?
- stimuli separated by an Interstimulus Interval (ISI)
- possible pairs
>different: <AB>, <BA>
>same: <AA>, <BB></BB></AA></BA></AB> - equal number of same and different pairs (usually)
Always counterbalance to reduce biases combinations
How are the results of an AX experiment measured?
- measures: accuracy (% correct) and reaction time
Describe an ABX design experiment
(Discrimination experiment)
- slightly more difficult than AX
- 3 stimuli presented in a series
- listener determines if it is A or B that is the same as the X
- other variations include AXB and XAB formats
- ‘X’ will be either ‘A’ or ‘B’
- each set of stimuli has 2 ISI’s
*can participants hear tiny difference between ‘A’ and ‘B’?
What is the approximate ISI used in most discrimination experiments?
- usually around 500ms each
Design elements of ABX design experiments
- often known as matching-to-sample
- 2 ISI’s, typically the same, but can vary
- bias concerns can arise due to temporal presentation order
- task slightly more complicated than AX, may require practice
Describe a 2AFC design
- Two Alternative Forced Choice (2AFC) Design
- 2 stimuli presented on each trial
- subjects discern the order of presentation
- typical instruction: “which stimulus came first, A or B?” “which stimulus had a higher tone?”
*no referent sounds or labels, just pick between first and second
What are the design elements of a 2AFC design?
- minimizes bias; ideal for similar stimuli
- assumes either order is equally possible
- requires discernment of stimulus order
- ex. Given 2 stimuli, asked “which tone is higher”?
Describe a 4IAX design
4-interval Forced Choice (4IAX) Design
- presentation of 4 sounds with binary choice
- subjects discern difference among the presented sounds
- 2 design alternatives: “oddity” version or same-different discrimination
- first and last stimuli are “flankers” (ie. first and last will never be the correct answer)
- Participants identify the unique sound
What are the design elements of the 4IAX design?
- possible presentations: <ABAA>, <AABA>, <BABB>, <BBAB></BBAB></BABB></AABA></ABAA>
- first and last stimuli “flankers” or “flanking stimuli”
- focus on discerning the order or uniqueness of the stimuli
What is a yes-no design?
- only one stimulus presented per trial
- subjects decided on the presence or nature of the stimulus
What are the elements of a yes-no design?
- can explore binary comparisons like X~not X, or y~not y
- multiple categories can be contrasted via blocking
