Introduction Can we improve memory for nonsense pics w/ cue? Method Study: See 28 pics (w/ or w/o label) Test: Immediate recall (draw)

Transcription

1 Chapter 9

2 Between-subject design (Bet-Ss) aka Between-participant design Experimental design and vocabulary Threats to internal validity Threats to external validity Within-subject design (W/in-Ss) aka Correlated-groups designs Within-participants design or Repeated measures design Participants complete all (2+) conditions. Researcher examines if difference between means e.g. pre-post-test, longitudinal study (vs. cross-sectional) Multiple testing sessions or complete conditions successively Matched-participants design

3 Introduction Can we improve memory for nonsense pics w/ cue? Method Study: See 28 pics (w/ or w/o label) Test: Immediate recall (draw) Results Label: 70% (SE= 1.25) No label 51% (SE=.92) t(16) = 3.43, p <.01 Discussion Memory significantly improved by use of verbal label Droodles by Roger Price a. 4 elephants sniffing an orange b. An early bird catching a very strong worm c. A man in a mailbox signaling a left turn

4 If Bower, Karlin, & Dueck was replicated using a within-subject design, what would it look like? What is the independent variable (IV)? What are the levels of the IV? What is the dependent variable (DV)? What is measured?

5 Bet-Ss desgin Ss Group Accuracy 1 no label 50 2 label 90 3 no label 60 4 label 85 5 no label 45 6 label 75 7 no label 30 8 label 90 W/in-Ss design Ss Acc-Label Acc-NoLabel MORE data from fewer Ss!!

6 Conditions Interference (s) Stroop experiment: say color of stimulus IV: condition (separate groups of Ss) Nonsense Rare Common Color- Associated Condition Interference (Seconds) Similar Color-Word Incongruent Color-Word

7 Duke undergraduates tested day after 9/11 (Flashbulb memory - FB) Tested again at 1, 6, or 32 weeks after 9/11 DV: consistency of FB and everyday memory Results: Both types of memory declined over time No relationship between accuracy and confidence in memory

8 Method IV: group (training vs. no training) IV: Training days on working memory task n-back DV: Performance on intelligence task before and after training sessions

9 Accuracy Method: Baseline task: Find repeated # in series of 10 #s Transformation task: Add or subtract 1 to each #, then find repeated # in series of 10 #s IV: Age (Yng v Older) DV: Accuracy Baseline Transformation Task conditions Yng Older

10 PRO Need fewer Ss (compared to bet-ss) Or get more data! Can take less time If all conditions are in 1 session rather than separate sessions for each Ss Increases POWER Decreases variability Less individual differences so more likely effect is due to IV not b/c Ss in grps are different CON Testing effects Fatigue effect Practice effect Order effect Carry-over effects ( transfer ) 1 st condition affects performance in 2 nd condition e.g. knowledge, attitude, etc. Increase in demand characteristics aka participant effects Ss has more info about the study so can change behavior

11 Distribute potential order effects evenly over groups by using counterbalancing techniques If use w/in-ss design for Bower, Karlin & Dueck ½ Ss receive label then no-label condition ½ Ss receive no label then label condition Complete counterbalancing If 4 conditions = 24 possible orders! Partial counterbalancing Randomly select orders to use Latin squares design Same # orders as # of conditions Each condition presented at each order\ E.g. 3 conditions: ABC / BCA / CAB

12 Gil Furman University Event-based vs. time-based PM Einstein & McDaniel (1990) Question: What is effect of cue familiarity on PM Method: Press key when see cue word Results: 3x more likely to press key for unfamiliar cue word than familiar cue word How likely are you to forget PM task? - Effect of background task - Effect of importance Kliegel et al (2004)

13 Use separate groups of Ss for each condition BUT, Ss for each condition are similar What variables should Ss be matched on? How many variables should Ss be matched on? It depends on the study! Used (more often) in clinical or drug research Match based on: Person variables (gender, age, ethnicity) Others such as intelligence, socioeconomic status Can also use natural pairs such as twins

14 Ss fill-out test of language ability Unknowingly primed w/ stereotypes of words in 1 of 3 categories Examine how quickly Ss interrupts conversation of experimenter w/ friend

15 PRO Eliminate testing effects (carry-over or order effects) Reduce demand characteristics (participant effects) Less variability among Ss compared to traditional bet- Ss design so increases power Can use statistics for w/in Ss design so there is more power than bet-ss design CON Need more Ss compared to w/in-ss design If loose 1 Ss from one group, loose matched Ss in other group (pair-wise loss) Need to decide what & # of characteristics to match Ss on Difficult to find matches (especially if mult. charcts) Reduces benefit of random selection (can loose benefit of random assignment)

16 Percent hits Percent false alarms 10 College students rate pronounceability of famous and nonfamous male and female names Familiar M Familiar F Unfamiliar M Unfamiliar F Later (24hrs/48hrs) judged whether each name was famous or not % 65% 68% 61% Male Female Familiar M Familiar F Unfamiliar M Unfamiliar F

17 How to prevent these potential confounds Nonequivalent control grp Use random assignment Use pretest/posttest design History Test at different time pts Maturation Use control group Testing effect Use control group Regression to mean Use control grp w/ same extreme scores Instrumentation effect Use control group Mortality or attrition Use control group Diffusion of treatment Tell Ss not to discuss study Experimenter or participant effects Use single-blind or doubleblind method Use placebo group Ceiling and floor effects Carefully select DV to avoid