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2 nd Year Practicals November 2008 Dr Jonathan Stirk Room C44 Office Hours: Wednesdays 10-11am Demonstrator: Maria Ktori.

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Presentation on theme: "2 nd Year Practicals November 2008 Dr Jonathan Stirk Room C44 Office Hours: Wednesdays 10-11am Demonstrator: Maria Ktori."— Presentation transcript:

1 2 nd Year Practicals November 2008 Dr Jonathan Stirk Room C44 Office Hours: Wednesdays 10-11am Demonstrator: Maria Ktori Contact by Room: A24 Office hour: Mondays 2pm

2 Selective Attention & the Flanker Compatibility Effect (FCE) Structure of practical Structure of practical –5 week structure Week 1 Mini-lecture, example expts, literature search Week 2 Develop hypothesis, select project Week 3 Pilot study, collect data Week 4 Data analysis (Mini-lecture) Week 5 Presentations Week 6 Hand in written report (Deadline Monday 8 th December, 2008 by 4pm.)

3 Aims of this practical To learn about the flanker compatibility effect To learn about the flanker compatibility effect To design an experiment to test a specific hypothesis about flanker effects To design an experiment to test a specific hypothesis about flanker effects To learn to implement a design using E- Prime software To learn to implement a design using E- Prime software To learn to collect and analyze data using computer software (E-Prime, SPSS) To learn to collect and analyze data using computer software (E-Prime, SPSS)

4 What is attention? Attention is the process of concentrating on specific features of the environment, or on certain thoughts or activities. This focusing on specific features of the environment usually leads to the exclusion of other features of the environment. Attention is the process of concentrating on specific features of the environment, or on certain thoughts or activities. This focusing on specific features of the environment usually leads to the exclusion of other features of the environment. Colman (2001) Colman (2001)

5 What is selective attention? 2 main types of attentional tasks 2 main types of attentional tasks –Divided attention tasks (dual tasks) Paying attention equally to more than one thing Paying attention equally to more than one thing –E.g. Reading out loud a story, whilst writing down dictated words (Spelke, Hurst & Neisser, 1976), driving whilst listening for a specific news item on the radio. –Selective attention tasks Paying attention to one source of information whilst ignoring everything else Paying attention to one source of information whilst ignoring everything else –E.g. Identifying words presented to the left ear, whilst ignoring words presented to the right ear in a dichotic listening task (Cherry, 1953)

6 Models of selective attention Where within the flow of information does specific information become selected and other information dismissed? i.e. When does selection take place? Where within the flow of information does specific information become selected and other information dismissed? i.e. When does selection take place? Does selection occur early in processing or later on? Does selection occur early in processing or later on? Sensory StoreResponse STIMULI Further processing Sensory StoreResponse STIMULI Further processing

7 Early versus late models of selective attention Early-selection models assume that selection occurs early-on in processing [after analysis of physical characteristics/features e.g. Broadbent (1958)]. From this point on unattended information receives little or no further processing. Early-selection models assume that selection occurs early-on in processing [after analysis of physical characteristics/features e.g. Broadbent (1958)]. From this point on unattended information receives little or no further processing. So NO semantic (identification) processing of the ignored/unattended information. So NO semantic (identification) processing of the ignored/unattended information.

8 Early versus late models of selective attention Late-selection models propose that ALL stimuli are analysed up to the point of identification (to a semantic level) and selection occurs after this point, i.e. later on in the processing stream. Late-selection models propose that ALL stimuli are analysed up to the point of identification (to a semantic level) and selection occurs after this point, i.e. later on in the processing stream. So to-be-ignored stimuli receive considerable processing and selection occurs much closer to the response end. So to-be-ignored stimuli receive considerable processing and selection occurs much closer to the response end.

9 Early and late selection Physical characteristics Meaning All messages in Selected message

10 BIG questions! Some questions in attentional research are: Some questions in attentional research are: To what extent are irrelevant stimuli processed in selective visual attention tasks? To what extent are irrelevant stimuli processed in selective visual attention tasks? How can we explain what is and isnt selected? How can we explain what is and isnt selected?

11 How can we examine the extent to which irrelevant information is processed? Priming studies Priming studies –Do to-be-ignored stimuli prime future performance on a cognitive task? Flanker tasks Flanker tasks –Do surrounding irrelevant stimuli affect performance on target stimuli? Eriksen & Eriksen (1974): classic flanker effect Eriksen & Eriksen (1974): classic flanker effect A response competition paradigm (similar to Stroop!) A response competition paradigm (similar to Stroop!) This is a selective visual attention task This is a selective visual attention task It can also be used to examine automatic processing of stimuli (processing without attention) It can also be used to examine automatic processing of stimuli (processing without attention) Or… Capture of attention by irrelevant stimuli Or… Capture of attention by irrelevant stimuli

12 Eriksen & Hoffman (1973) Original expt used circular displays of letters and Ss had to identify the presence of a target (out of 4 possible targets) flanked by distracters Original expt used circular displays of letters and Ss had to identify the presence of a target (out of 4 possible targets) flanked by distracters H H AA H M UM U U M U

13 The flanker compatibility effect Flankers are stimuli which are presented spatially close to target stimuli and which should be ignored Flankers are stimuli which are presented spatially close to target stimuli and which should be ignored Despite the irrelevance of flankers to the target task they are often shown to interfere with target responses Despite the irrelevance of flankers to the target task they are often shown to interfere with target responses The original task involved being presented with 5 letter strings and determining the identity of the middle letter by moving a lever to the left or right The original task involved being presented with 5 letter strings and determining the identity of the middle letter by moving a lever to the left or right More modern versions involve left and right hands pressing specific buttons/keys to identify a target More modern versions involve left and right hands pressing specific buttons/keys to identify a target

14 Eriksen et al (1974): linear display task LEFT HAND RESPONSE RIGHT HAND RESPONSE Target:HKSC H H K H H E.g.Respond left S S C S S E.g.Respond right flankers target REVERSE MAPPINGS CAN BE USED TOO!

15 Compatibility of responses However, the compatibility of the target and flanker responses is important However, the compatibility of the target and flanker responses is important RT to target: RT to target: Incompatible trials > Compatible trials StimuliCompatibilityResponse hand TargetFlanker HHKHHCompatibleLKH KKHKKCompatibleLHK SSCSSCompatibleRCS CCSCCCompatibleRSC SSKSSIncompatibleLKS CCKCCIncompatibleLKC CCHCCIncompatibleLHC SSHSSIncompatibleLHS HHCHHIncompatibleRCH KKCKKIncompatibleRCK HHSHHIncompatibleRSH KKSKKIncompatibleRSK

16 Defining the flanker compatibility effect The FCE is the difference in RT between the two types of compatibility trials The FCE is the difference in RT between the two types of compatibility trials FCE = Incompatible trials – compatible trials FCE = Incompatible trials – compatible trials E.g. 500 ms-420 ms FCE of 80ms E.g. 500 ms-420 ms FCE of 80ms Sometimes the effect is measured with respect to a base-line condition Sometimes the effect is measured with respect to a base-line condition –One in which flankers are Neutral with respect to target responses –E.g XXSXX (where the X flanker does not belong to the target set) –RT differences can then be framed as costs or benefits i.e. we can examine facilitation and interference i.e. we can examine facilitation and interference

17 What factors moderate the FCE? Research has shown that the FCE is quite robust Research has shown that the FCE is quite robust However, a number of factors have been shown to moderate the effect However, a number of factors have been shown to moderate the effect Early research suggested that flanker-target distance was important Early research suggested that flanker-target distance was important –Eriksen & Eriksen (1974) showed that larger spatial separation (eccentricity) reduced the FCE –Distracters within 1° of visual angle could not be ignored –Possible evidence for a fixed-width spotlight of selective attention (Posner, 1980)

18 Fixed-width spotlight metaphor S C S < 1 deg Fixed width (2 deg) Flankers cannot be ignored as they are within the space selected for attention

19 Fixed-width spotlight metaphor S C S > 1 deg Fixed width (2 deg) Flankers may now receive less processing

20 Explanations of separation effects The spotlight metaphor helps to explain the effects of target-flanker separation on the FCE. The spotlight metaphor helps to explain the effects of target-flanker separation on the FCE. However, other explanations are viable However, other explanations are viable –Visual acuity decreases the further objects are from the point of fixation So perhaps increasing the size of flankers/targets is important in controlling for acuity problems So perhaps increasing the size of flankers/targets is important in controlling for acuity problems –Distance is confounded by Gestalt grouping The law of proximity suggests that closeness effects grouping of stimuli The law of proximity suggests that closeness effects grouping of stimuli

21 Law of proximity Grouped by column Grouped by row

22 So does perceptual grouping affect the FCE? What if attention is to objects rather than space? What if attention is to objects rather than space? –If attention is object-based then principles of grouping may affect what is selected for further processing –Driver & Baylis (1989) used common motion to compete the distance vs grouping hypotheses

23 Driver & Baylis (1989) TTHXH The results showed that moving distant distracters (e.g. the Hs above) produced more interference than the static closer distracters (e.g. the Ts above). So, perceptual grouping seems important in the allocation of attention and in the FCE

24 Further effects of grouping Harms & Bundesen (1983) Harms & Bundesen (1983) –Used colour segregation of targets/distracters –E.g. (1) F T F versus (2) F T F –This encouraged colour segregation of targets/distracters in condition 2 –Smaller flanker compatibility effects in condition 2

25 Further factors moderating FCE Miller (1991) manipulated five factors to try and eliminate the FCE and determine any boundary conditions Miller (1991) manipulated five factors to try and eliminate the FCE and determine any boundary conditions 1.Poor spatial resolution 2.Inability to hold attentional focus on a fixed location 3.Inability to focus completely on an empty display location 4.Inability to filter out stimuli which onset at the same time as the target during the task 5.Inability to prevent analysis of all stimuli when there is insufficient demand by the attended items

26 Consistent & varied mapping Miller hypothesised that we are unable to maintain attention on a fixed location and this may be why attention leaks to the irrelevant distracters Miller hypothesised that we are unable to maintain attention on a fixed location and this may be why attention leaks to the irrelevant distracters In the linear task the target is always in the same spatial location In the linear task the target is always in the same spatial location So, he varied the locations of targets/distracters and used a __ (bar) pre-cue to direct attention to the location So, he varied the locations of targets/distracters and used a __ (bar) pre-cue to direct attention to the location The FCE was NOT diminished when varied mapping was used The FCE was NOT diminished when varied mapping was used

27 +

28 H XX

29 Millers Boundary Conditions Perhaps it is not the constancy but rather the emptiness of the attended location which prevents early selection from fully excluding other locations from further processing Perhaps it is not the constancy but rather the emptiness of the attended location which prevents early selection from fully excluding other locations from further processing Necessary object hypothesis Necessary object hypothesis Miller used an RSVP version of the flanker task to test this Miller used an RSVP version of the flanker task to test this

30 RSVP task The necessary object hypothesis predicts an FCE only when the target appears in frame 1 (as there is no previous object in the target location) The necessary object hypothesis predicts an FCE only when the target appears in frame 1 (as there is no previous object in the target location) However, results showed that the FCE was present in later frames refuting the hypothesis However, results showed that the FCE was present in later frames refuting the hypothesis F = flankerT = target 200ms

31 Millers Boundary Conditions Maybe we cant filter out flankers because they onset at the same time as the target Maybe we cant filter out flankers because they onset at the same time as the target –Yantis & Jonides (1984) had shown that abrupt onsets attract attention in a visual task Miller varied onset/offset transients of flankers/targets Miller varied onset/offset transients of flankers/targets Used figure 8 concept. Used figure 8 concept.

32 Yantis & Jonides figure 8 Results showed that transients had no effect on the FCE Results showed that transients had no effect on the FCE Transients therefore do not seem to be responsible for the partial leakage of unattended stimuli through an early selection mechanism. Transients therefore do not seem to be responsible for the partial leakage of unattended stimuli through an early selection mechanism.

33 Millers Boundary Conditions What if processing of the irrelevant flankers is because attentional capacity is underloaded leaving room for processing of the flankers? What if processing of the irrelevant flankers is because attentional capacity is underloaded leaving room for processing of the flankers? –Perceptual underload hypothesis So Miller varied the amount of relevant information and examined the FCE So Miller varied the amount of relevant information and examined the FCE

34 Perceptual Underload Stimuli Flankers TARGET (attended) REGION Number of letters varied

35 Perceptual Underload Stimuli Results showed that the FCE was eliminated for the larger set sizes Results showed that the FCE was eliminated for the larger set sizes Finally a boundary condition for FCE? Finally a boundary condition for FCE? –NO as there was a confound of timing Further experiments did NOT support the underload hypothesis Further experiments did NOT support the underload hypothesis

36 So what are you going to do? Get into small groups (3) and design an experiment to investigate a factor which may effect the FCE Get into small groups (3) and design an experiment to investigate a factor which may effect the FCE Design needs to be at least a 2 x 2 factorial design Design needs to be at least a 2 x 2 factorial design –E.g. 2 IVs! 1. Compatibility of flankers (compatible vs. incompatible) 1. Compatibility of flankers (compatible vs. incompatible) 2. Other variable of your own! 2. Other variable of your own!

37 Examples of factors to manipulate Any grouping factor e.g. Colour segregation Any grouping factor e.g. Colour segregation –Harms & Bundesen (1983) Number of flankers? Number of flankers? Nature of flankers? Nature of flankers? –Pictures vs. words? Target-flanker separation Target-flanker separation E.t.c. E.t.c.

38 So for example… manipulate distance S,C left H,K right (response pairings) CompatibleIncompatible Near S C S H C H Far S C S H C H Leads to 4 conditions (cells) in the design, tested within-subjects

39 How are you going to do this? Using E-Prime to control stimulus display Using E-Prime to control stimulus display Create stimuli materials in E-Prime or maybe using Paint or other graphics program (PowerPoint plus Paint) Create stimuli materials in E-Prime or maybe using Paint or other graphics program (PowerPoint plus Paint) DEMO OF TEMPLATE (using letter stimuli and manipulating target-flanker DISTANCE) DEMO OF TEMPLATE (using letter stimuli and manipulating target-flanker DISTANCE)

40

41 So minimum number of trials is 32 Samples need to be weighted to balance out compatible/incompatible trials

42 What to do - recap So choose a further IV that you can manipulate at 2 levels So choose a further IV that you can manipulate at 2 levels –E.g. you may manipulate a grouping factor at 2 levels –You might look at what type of information (e.g. semantic?) can influence target response Create stimuli for your experiment Create stimuli for your experiment Program E-Prime Program E-Prime Run design Run design

43 Types of flanker tasks you can use Classic Letter flanker task S C S Classic Letter flanker task S C S Colour flanker task * * * (Left- red/white, Right- Blue,green) respond to target colour Colour flanker task * * * (Left- red/white, Right- Blue,green) respond to target colour Letter-number task 2 A 2 (classify target as either a letter or a number) Letter-number task 2 A 2 (classify target as either a letter or a number) Spatial/Arrows flanker task < Semantic classification flanker task Semantic classification flanker task –Classify names as male/female E.g. John Samantha John (incompat) vs. E.g. John Samantha John (incompat) vs. June Samantha June (compat) –Classify target as large/small etc. Remember this is essentially a response competition paradigm. If target responses are slowed then it must be because of some flanker processing. Remember this is essentially a response competition paradigm. If target responses are slowed then it must be because of some flanker processing.

44 Some References Bindemann, M., Burton, A., & Jenkins, R. (2005). Capacity limits for face processing. Cognition, 98(2), Bindemann, M., Burton, A., & Jenkins, R. (2005). Capacity limits for face processing. Cognition, 98(2), Diedrichsen, J., Ivry, R.B., Cohen, A. & Danziger, S. (2000). Asymmetries in a unilateral flanker task depend on the direction of the response: The role of attentional shift and perceptual grouping. Journal of Experimental Psychology: Human Perception and Performance, 26, Diedrichsen, J., Ivry, R.B., Cohen, A. & Danziger, S. (2000). Asymmetries in a unilateral flanker task depend on the direction of the response: The role of attentional shift and perceptual grouping. Journal of Experimental Psychology: Human Perception and Performance, 26, Driver, J. & Baylis, G.C. (1989). Movement and visual attention: the spotlight metaphor breaks down. Journal of Experimental Psychology: Human Perception & Performance, 15(3), Driver, J. & Baylis, G.C. (1989). Movement and visual attention: the spotlight metaphor breaks down. Journal of Experimental Psychology: Human Perception & Performance, 15(3), Eriksen, B. A., & Eriksen, C. W. (1974). Effects of noise letters upon the identification of a target letter in a nonsearch task. Perception & Psychophysics, 16, Eriksen, B. A., & Eriksen, C. W. (1974). Effects of noise letters upon the identification of a target letter in a nonsearch task. Perception & Psychophysics, 16, Eriksen, C.W. (1995). The flankers task and response competition: a useful tool for investigating a variety of cognitive problems. Visual Cognition, 2, (available as a.pdf from me) Eriksen, C.W. (1995). The flankers task and response competition: a useful tool for investigating a variety of cognitive problems. Visual Cognition, 2, (available as a.pdf from me) Harms, L & Bundesen, C. (1983). Color segregation and selective attention in a nonsearch task. Perception & Psychophysics, 33, Harms, L & Bundesen, C. (1983). Color segregation and selective attention in a nonsearch task. Perception & Psychophysics, 33,

45 Some References Miller, J. (1991). The flanker compatibility effect as a function of visual angle, attentional focus, visual transients, and perceptual load: a search for boundary conditions. Perception & Psychophysics, 49 (3), Miller, J. (1991). The flanker compatibility effect as a function of visual angle, attentional focus, visual transients, and perceptual load: a search for boundary conditions. Perception & Psychophysics, 49 (3), Shomstein, S. & Yantis, S. (2002). Object-based attention: sensory modulation or priority setting? Perception & Psychophysics, 64(1), Shomstein, S. & Yantis, S. (2002). Object-based attention: sensory modulation or priority setting? Perception & Psychophysics, 64(1), Styles, E. (1997). The psychology of attention. UK: Psychology Press [Chapter 3] Styles, E. (1997). The psychology of attention. UK: Psychology Press [Chapter 3] Jenkins, R., Lavie, N. & Driver, J. (2003). Ignoring famous faces: category-specific dilution of distractor interference. Perception and Psychophysics, 65(2), Jenkins, R., Lavie, N. & Driver, J. (2003). Ignoring famous faces: category-specific dilution of distractor interference. Perception and Psychophysics, 65(2), Lachter, J., Forster, K. I., & Ruthruff, E. (2004). Forty-five years after Broadbent (1958): Still no identification without attention. Psychological Review, 111(4), Lachter, J., Forster, K. I., & Ruthruff, E. (2004). Forty-five years after Broadbent (1958): Still no identification without attention. Psychological Review, 111(4),


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