Dramatically Larger Flanker Effects E81 Sarah Munro, Cecil Chau, Karine Gazarian, & Adele Diamond 3 mm Sample Stimulus in Study 2 200 150 100 50 > or OUTSIDE > < OUTSIDE > Study 1: 96 young adults Study 2: 32 young adults Both studies: 50% female; mean age 22 years 50% Chinese Canadians; 50% European Canadians 200 150 100 50 BLOCK BLOCK 3 1 (MIXED) 14 x larger in mixed block 123 msec difference BLOCK BLOCK 3 (MIXED) 1 6 x larger in mixed block 74 msec difference Out Small Study 2 250 NS 150 100 50 0 STUDY 1 STUDY 2 Large Small STUDY 1 STUDY 2 Small Large However, in the Mixed-task block, the Flanker effect was much less sensitive to the size or dispersion of the stimuli. There was no significant difference in the size of the Flanker effect in the Mixed block in Studies 1 or 2. 0.10 Smaller, Closer Stimuli (Study 2) Only Studies 1 and 2 Combined 0.05 BLOCK BLOCK 3 (MIXED) 1 BLOCK BLOCK 3 1 (MIXED) 10 x larger in mixed block SEPARATED CUE INTEGRATED CUE 300 BLOCK 1 (Standard Flanker) BLOCK 3 (MIXED) 250 NS 200 150 100 50 0 SQUARES ARROWS SQUARES ARROWS 300 250 BLOCK 3 (MIXED) BLOCK 1 (Standard Flanker) NS BLOCK 5 (Standard Flanker) 200 150 100 50 0 Squares Arrows Squares Arrows Squares Arrows In the standard flanker condition, the type of stimulus used significantly affected the size of the Flanker effect. The Flanker effect was much larger for Iconic Stimuli (Arrows) than for Symbolic Stimuli (Squares). However, in the Mixed-task block, the Flanker effect was insensitive to stimulus type. There was no significant difference in the size of the Flanker effect in the Mixed block whether arrows or squares served as the stimuli. 250 NOT DUE TO PRACTICE EFFECTS 200 150 Flanker Effect by Block for Study 2 Non-Switch Trials Only 100 50 0 BLOCK BLOCK 3 (MIXED) 1 75 x larger in mixed block 213 msec difference BLOCK BLOCK 3 1 (MIXED) 72 x larger in mixed block 144 msec difference Regardless of whether the cue indicating which rule to follow (focus on central figure or flankers) was part of the stimuli (their shape – the Integrated Cue condition) or external to the stimuli (the background color – the Separated Cue condition), the Flanker effect was much larger in the Mixed Block than in the Single Task Block. This was true for the standard flanker condition and for focus-on-the-flanker trials. 300 Block 1 Block 2 Block 3 (Mixed) Block 4 Block 5 250 200 150 100 50 0 IN OUT IN OUT IN OUT IN OUT OUTSIDE > < OUTSIDE OUTSIDE < OUTSIDE > < INSIDE > INSIDE < INSIDE > OUTSIDE < OUTSIDE > OUTSIDE < OUTSIDE > Mean RT for each Trial Type for Inside, Non-Switch Trials in Study 2 505 495 485 475 465 455 445 435 425 415 BLOCK 1 (Standard Flanker) BLOCK 3 (MIXED) 1050 1000 950 900 850 800 750 700 650 600 Cong No- Neu Incong Cong No- Neu Incong Dis Dis Congruent and No-Distractor trials were equally easy in the standard Flanker task, but No-Distractor trials were far easier in the Mixed condition. CONCLUSIONS MAIN FINDINGS: Squares vs. Arrows for Standard and Mixed Blocks Inside Non-Switch Trials 0.15 > Order of trial types was counterbalanced within blocks. Percentage of each trial type was: 43% Incongruent, 29% Congruent, 14% Neutral, and 14% No-Distractor trials. RT in msec Consistent with past studies, we found a larger Flanker effect in the Standard Flanker task block (Block 1) when the stimuli were smaller and closer (Study 2) than when they were larger and farther apart (Study 1). The Flanker effect was far smaller with the larger stimuli. BLOCK 3 (Mixed Block) 200 0.20 300 BLOCK 1 (Standard Flanker) INSIDE Large Study 1 Small Study 2 In < Out In INSIDE Flanker Effect in msec Relative Flanker Effect INTEGRATED CUE 300 Stimulus Size: 0.25 OUTSIDE 250 0 INSIDE SEPARATED CUE Out Larger, Farther Apart Stimuli (Study 1) vs. Smaller, Closer Stimuli (Study 2) for Standard Flanker Blocks and Mixed Blocks (Inside Non-Switch Trials) 0.30 49 x larger in mixed block 16 x larger in mixed block 223 msec difference Flanker Effect in msec Flanker Effect in msec > The other 50% of subjects in Study 1 were tested with an Integrated Cue (the Stimulus Shape): or > Rules: If images are, If images are, or focus on the INSIDE stimulus focus on the OUTSIDE stimulus < 0.35 0 BLOCK BLOCK 3 (MIXED) 1 STUDY 2 0.40 INSIDE 300 INSIDE 0.45 STUDY 1 Flanker Effect in Block 1 vs. Block 3 (Mixed Block) Non-Switch Trials If pink background, focus on the OUTSIDE stimulus OUTSIDE Relative RT difference: (I – C) / C “Outside” Trials (ignore the center stimulus) also show a dramatic increase in the “Flanker” effect between the Single-Task block (focus only on the Outside stimuli) and the Mixed-Task block (on some trials focus on the Inside, on some trials focus on the Outside). This was true for both studies and for both the absolute “Flanker” effect and correcting for longer RTs in the Mixed Block (right-hand figure). All subjects in Study 2 and half the subjects in Study 1 were tested with a Separated Cue (the Background Color): < BLOCK BLOCK 3 1 (MIXED) 80 x larger in mixed block 227 msec difference Half were tested with Symbolic Stimuli: e.g., or Rules: For White, press Left. For Black, press Right. OUTSIDE STUDY 2 250 0 These are the stimulus parameters used in most Flanker experiments. > 3 x larger in mixed block Flanker Effect in msec 300 STUDY 1 Large Study 1 In INSIDE INTEGRATED CUE Main Result, 2: MORE ROBUST FLANKER EFFECT IN MIXED BLOCK (Less sensitive to changes in stimulus size or dispersion) BLOCK BLOCK 3 (MIXED) 1 Flanker Effect in msec 16 mm x 16 mm INSIDE 3 x larger in mixed block Relative Flanker Effect 8 mm < BLOCK BLOCK 3 1 (MIXED) Both studies show a large increase in the Flanker effect between the standard Flanker condition (Block 1; focus on the Inside figure) and the Mixed-Task block (Block 3; on some trials focus on the Inside and on some trials focus on the Outside). RT was longer on all trials in the Mixed Block, but as the right-hand figure shows, the Flanker effect is still much amplified in the Mixed Block when the effect is scaled to the baseline (Congruent) RT. Flanker Effect in msec In Study 1, the stimuli were larger & farther apart than in Study 2: INSIDE 6x larger in mixed block 108 msec difference Stimulus Size: Out > 14 x larger in mixed block 163 msec difference In 0.05 0 BLOCK BLOCK 3 (MIXED) 1 0 0.10 RT Difference: Incongruent minus Congruent Study 2 included single-task blocks of only Inside and only Outside trials both before and after the Mixed block (counterbalancing the order of the 2 single-task blocks). Rules: If blue background, focus on the INSIDE stimulus BLOCK BLOCK 3 (MIXED) 1 0.15 50 INSIDE 50 0.20 100 < 100 0.25 150 INSIDE 150 0.30 STUDY 2: Smaller, Closer Stimuli Block 1 vs. Block 3 (Mixed Block) Outside Non-Switch Trials Only Study 1 included one block of each type, the single-task blocks before the Mixed block. Half the subjects were tested with Iconic Stimuli: < Rule: Press where the stimulus is pointing 200 0.35 STUDY 1: Large Stimuli, Farther Apart 200 OUTSIDE No Distractor Neutral Neutral All subjects received 3 kinds of trial blocks: Inside-Only Outside-Only Both Trial Types Intermixed 10 practice trials before each 16 practice trials 70 trials per block 180 trials Half the subjects received Inside-Only first. Half the subjects received Outside-Only first. Sample Stimulus in Study 1 250 0 METHODS 36 mm x 36 mm 300 STUDY 2: Smaller, Closer Stimuli STUDY 1: Large Stimuli, Farther Apart Relative RT difference: (I – C) / C 250 INSIDE No Distractor Flanker Effect in msec RT Difference: Incongruent minus Congruent 300 Block 3 (Mixed Block) SEPARATED CUE Our prediction was resoundingly confirmed. The Flanker effect was dramatically larger in the mixed-condition than in single-task blocks (in both cases comparing non-switch incongruent and congruent trials). It was also much less sensitive to variations in stimulus characteristics. Block 1 (Standard Flanker) vs. Block 3 (Mixed Block) Inside Non-Switch Trials Only Block 1 (Single-Task Block) IN SUMMARY, regardless of - stimulus size or the distance between stimuli (Study 1 vs. Study 2), - whether subjects had to focus on the Inside or the Outside on a given trial, - whether the cue was Integrated with the stimuli or the color of the background, or - whether the Flanker effect was calculated as Incongruent minus Congruent RT or the ratio of that to baseline (Congruent) RT, the Flanker effect was dramatically larger when subjects could not stay focused on just the inside or just the outside, but had to periodically switch the focus of their attention across trials. We hypothesized that the reason for that is because subjects can settle into concentrating on the central location. We therefore predicted that if a switching component were added, requiring subjects to sometimes focus on the flankers and sometimes on the central stimulus, that the flanker effect would be far larger and far more robust (less sensitive to stimulus size or distance between stimuli). Summary for Main Result, 1: Block 1 vs. Block 3 Non-Switch Trials Flanker Effect in msec The classic Flanker effect is highly replicable but relatively small and fragile (i.e., very sensitive to stimulus characteristics). Besides congruent and incongruent trial types, there were also No-Distractor and Neutral trials: Main Result, 1: FAR LARGER FLANKER EFFECT IN MIXED BLOCK Flanker Effect in msec ABBREVIATED ABSTRACT email: [email protected] Department of Psychiatry, University of British Columbia, 2255 Wesbrook Mall, Vancouver, BC, Canada V6T 2A1 IN OUT Early or late in the session, before or after the Mixed Block, the Flanker effect was far smaller when subjects did not have to change the focus of their attention, whether they were focusing on the center or on the outside. The size of the flanker effect for inside-only or outside-only trials was similar in Blocks 1, 2, 4, and 5. This also indicates that the size of the Flanker effect was not affected by the preceding block of trials. The much larger Flanker effect in the Mixed block cannot be explained by practice effects. • When observers were allowed to consistently focus on a specific area (either Inside-only or Outside-only), the Flanker effect was much smaller than when subjects did not know in advance whether the target would be in the center or the outside. • The Flanker effect for Inside-only and Outside-only blocks was very susceptible to disruption by increasing the size and dispersion of the stimuli or by using stimuli less directly, automatically tied to the response. • When observers had to randomly switch mindsets and the focus of their attention across trials (Mixed block), the Flanker effect increased dramatically in size and became significantly more robust and resistant to disruption due to changes in the physical • The much larger Flanker effect in the Mixed block was true regardless of stimulus type (iconic or symbolic), stimulus size or spacing (large, farther apart or small, closer together), cue-type (an integrated aspect of the stimuli themselves or the color of the background), block order (whether preceded by a block where all trials had the other rule, intermixed rules, or no preceding block), whether early or late in a session, which rule was in effect (press where the central stimulus tells you, or press where the outer stimuli tell you), or how flanker effect was calculated (diffference in absolute RT or that difference as a fraction of baseline RT). • The dramatically larger Flanker effect in the Mixed block cannot be attributed to practice effects or longer to RTs on all trials in the Mixed block. OTHER FINDINGS: • Gender and age had no significant effect on RT or the Flanker effect. • Participants whose first language was Chinese showed larger Flanker effects than non-Chinese participants for trials in which the outer stimuli were the target. This research was supported by an R01 grant from NIDA (#DA19685-16A2).