Using the psychophysics of choice behaviours to infer menta - PowerPoint Presentation

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Using the psychophysics of choice behaviours to infer menta - PPT Presentation

Tom Stafford Department of Psychology University of Sheffield tstaffordshefacuk Galway 15 th of January 2010 Conclusions It is not possible to infer discrete processing stages from the appearance of additive factors ID: 201697

sheffield university decision amp university sheffield amp decision processing additive stroop task stage stimulus factors response making stages single

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Slide1

Using the psychophysics of choice behaviours to infer mental structure from reaction times

Tom

Stafford, Department

of Psychology, University of

Sheffield, t.stafford@shef.ac.uk

Galway, 15

of January, 2010Slide2

ConclusionsIt is not possible to infer discrete processing stages from the appearance of additive factorsExperimental and modelling work involving Pieron’s Law gives a worked exampleBUT It is also unlikely that simple perceptual decision making is simple, even in paradigmatic cases30/07/09

Image thanks to Roger CarpenterSlide4

30/07/09© The University of SheffieldSlide5

The additive factors method30/07/09© The University of Sheffield

Sternberg, S. (1969) The discovery of processing stages: Extensions of

Donders

' method.

In W. G.

Koster

(Ed.), Attention and performance II.

Acta

Psychologica

, 30

, 276-315.

Input

Stage 1

Stage 2

Output

Factor A

Factor B

Effect A

Effect B

Factors A + B

Effect A + B?Slide6

Additive Factors Method (AFM)

The application of this method has produced consistent support for the existence of separate stages in decision making,

particularly the independence of stimulus processing and response selection (e.g.

Stoffels

, 1996;

Wildenberg

Molen

, 2004)

30/07/09

Stoffels

, E. J. (1996). On stage robustness and response selection routes: Further

evidence.

Acta

Psychologica

, 91

(1), 67-88.

Wildenberg

, W. P. van den, &

Molen

, M. W. van der. (2004). Additive factors

analysis of inhibitory processing in the stop-signal paradigm.

Brain & Cognition,

(2), 253-66.Slide7

Stages to decision making? (1)‏

‘‘Most research on AFM shows consistent and robust evidence in

favor

of seven successive processing stages in traditional choice reactions” (Sanders, 1990)‏

“information is transmitted discretely between perceptual and response stages of processing” (Woodman et al, 2008)‏

30/07/09

Sanders, A. F. (1990). Issues and trends in the debate on discrete

continuous

processing of information.

Acta

Psychologica

, 74

(2-3), 123-167.

Woodman, G. F., Kang, M. S., Thompson, K., &

Schall

, J. D. (2008). The effect of visual search efficiency on response preparation:

neurophysiological

evidence for discrete flow.

Psychological Science, 19

(2), 128-136.Slide8

Stages to decision making? (2)‏

PDP framework (Rumelhart et al, 1986) explicitly rejects stage models, in favour of continuous processing (McClelland, 1979)‏

Most successful model of RTs is single stage, Ratcliff's diffusion model‏

30/07/09

Rumelhart, D., McClelland, J. & the PDP Research Group (Eds.),

Parallel distributed processing: Explorations in the microstructure of cognition

. Cambridge, MA: MIT Press.

McClelland, J. (1979). On the time-relations of mental processes: An examination of systems of processes in cascade.

Psychological Review, 86

, 287-330.Slide9

30/07/09

The diffusion model of decision making

Ratcliff, R. (1978). A theory of memory retrieval.

Psychological Review

(2), 59-108.

Ratcliff, R., & McKoon, G. (2008). The diffusion decision model: Theory and data for two-choice decision tasks.

Neural computation

(4), 873-922. Slide10

30/07/09© The University of Sheffield

Gold, J. I., &

Shadlen

, M. N. (2002).

Banburismus

and the brain decoding the relationship between sensory stimuli, decisions, and reward.

Neuron, 36

(2), 299-308.

Neural instantiation of ‘accumulated evidence’ found in area LIP?

Figure 4, Gold &

Shadlen

(2002)Slide11

30/07/09

Modelling

decision

making

‘decision making’ research has focused on perceptual decisions (e.g. Gold &

Shadlen

, 2007)‏

Diffusion model has been shown to be optimal (

Bogacz

et al, 2006)‏

Optimal processing seems to require integration of factors influencing a decision into a single variable (e.g. Ratcliff, 2001?)‏

Bogacz

, R., Brown, E.,

Moehlis

, J., Holmes, P., & Cohen, J. D. (2006). The physics of optimal decision making: a formal analysis of models of performance in two-alternative forced-choice tasks.

Psychological Review, 113

(4), 700-65.

Gold, J. I., &

Shadlen

, M. N. (2007). The neural basis of decision making.

Annual Review of Neuroscience, 30

, 535-574

Ratcliff, R. (2001). Putting noise into

neurophysiological

models of simple decision making.

Nature Neuroscience, 4

(4), 336-336.Slide12

Task: to inspect RTs in a more complex‏ choice task, something that is not just a perceptual decision

...a decision which involves two factors, which provide evidence that (we might assume) is represented at different stages

Are reaction times affected additively by these two factors?

Can existing single stage models account for the pattern of results?Slide13

The Stroop

Task

30/07/09

Stroop

, J. (1935). Studies of interference in serial verbal reactions.

Journal of Experimental Psychology, 18

, 643-662.

Stafford, T., & Gurney, K. (2007). Biologically constrained action selection improves cognitive control in a model of the

Stroop

task.

Philosophical Transactions of the Royal Society London, Series B, 362

, 1671-1684.

Stroop

(1935)Slide14

The Stroop Task

Name the colour

Control

SHOE

30/07/09

14Slide15

The Stroop Task

Name the colour

Control

SHOE

Congruent

GREEN

30/07/09

15Slide16

The Stroop Task

Name the colour

Control

SHOE

Congruent

GREEN

Conflict

BLUE

30/07/09

16Slide17

30/07/09

The stimulus intensity – reaction time function

aka ‘Piéron’s Law’

RT = R

Pieron, H. (1952).

The sensations; their functions, processes and mechanisms: Their Functions, Processes, and Mechanisms

. Yale University Press.Slide18

Pieron's

Law found for white light, pure tones, taste...(Luce, 1986)‏

...and in simple choice decisions (Pins & Bonnet, 1996)‏

“luminance processing and any further processing due to the specific requirements of the psychophysical task combine additively”

Rumelhart

, D., McClelland, J. & the PDP Research Group (Eds.),

Parallel distributed processing: Explorations in the microstructure of cognition

. Cambridge, MA: MIT Press.

Luce, R. D. (1986).

Response times: Their role in inferring elementary mental organization.

Oxford University

Press.

Pins, D., & Bonnet, C. (1996). On the relation between stimulus intensity and processing time:

Piéron's

law and choice reaction time.

Perception and Psychophysics, 58

(3), 390-400Slide19

30/07/09

Piéron’s Law inherent in any rise-to-threshold decision process

Stafford, T., & Gurney, K. N. (2004). The role of response mechanisms in determining reaction time performance:

Pieron’s

law revisited.

Psychonomic

Bulletin & Review

(6), 975-987

Palmer, J.,

Huk

, A. C., &

Shadlen

, M. N. (2005). The effect of stimulus strength on the speed and accuracy of a perceptual decision.

Journal of Vision, 5

(5), 376-404.Slide20

30/07/09

Expt 1:

A Stroop task with varying levels of colour saturationSlide21

30/07/09

If saturation and response conflict information are integrated then the different Stroop conditions should differ by different amounts at each level of saturationSlide22

InteractiveSlide23

Additive

InteractiveSlide24

Expt 1 Results, i

30/07/09

Colour saturation (%)‏

Reaction Time (ms)‏Slide25

Expt 1 Results, ii

30/07/09

25Slide26

30/07/09

Expt 2:

A Stroop task with varying levels of colour saturation,

with word and colour elements of the stimulus separated in spaceSlide27

Expt 2 Results, i

30/07/09

Colour saturation (%)‏

Reaction Time (ms)‏Slide28

Expt 2 Results, ii

30/07/09

28Slide29

30/07/09

Cohen et al’s (1990) model of Stroop processing

Cohen, J. D., Dunbar, K., & McClelland, J. L. (1990). On the control of automatic processes - a parallel distributed-processing account of the stroop effect.

Psychological Review, 97

(3), 332-361.Slide30

30/07/09

Stimulus

Stimulus-Response

Translation

RTSlide31

30/07/09

Stimulus

Stimulus-Response

Translation

SSlide32

30/07/09

Stimulus

Stimulus-Response

Translation

SSlide33

30/07/09

Simulation Results, iSlide34

30/07/09

Simulation Results, iiSlide35

Interim conclusions (1/2)

Empirical findings

ron’s

Law holds for colour saturation…

….in a complex choice task

30/07/09

35Slide36

Interim conclusions (2/2)

Stimulus intensity and response conflict appear additive in a colour-saturation variant of the

Stroop

task

...but existing continuous-processing single-stage models of the

Stroop

task are adequate to account for this result

We must be careful before inferring discrete stages from additive RT data

30/07/09

Stafford, T., Gurney, K.N. & Ingram, L. (2009).

Piéron’s

Law holds in conditions of response conflict. In N.A.

Taatgen

& H. van Rijn (Eds.),

Proceedings of the 31th Annual Conference of the Cognitive Science Society

. Cognitive Science Society.Slide37

Modelling explorationsAppearance of additive and interactive factors can be generated by both single stage and multiple stage modelsFor the current task, another factor determines additivity --- whether stimulus inputs are bound together or not

30/07/09

Currently…

‘locked inputs’

(‘single stage’/continuous processing)Slide39

Now…

Independent inputs

(Still ‘single stage’)Slide40

Simulation independent inputs, single stage,

Result: interactive factorsSlide41

Locked inputs, ‘two stage’

SSlide42

Result: additive factors

Simulation: locked inputs, two stageSlide43

Independent inputs, two stage

1Slide44

Results: interactive factors

Simulation: independent inputs, two stagesSlide45

Decision making:

Single stage

/continuous

Multiple stage

/discrete

Additive

Interactive

InteractiveSlide46

Modelling conclusionAn illustration of the phenomenon of model-mimickry (Townsend & Wenger, 2004) and more generally of the dangers of judging models solely by the goodness of fit to data (Roberts & Pashler, 2000).

30/07/09

Townsend, J. T., & Wenger, M. J. (2004). The serial-parallel dilemma: A case study in a linkage of theory and method.

Psychonomic

Bulletin & Review, 11

(3), 391-418. (1069-9384)… See also Thomas, R. D. (2006). Processing time predictions of current models of perception in the classic additive factors paradigm.

Journal Of Mathematical Psychology, 50

(5), 441-455.

Roberts, S., &

Pashler

, H. (2000). How persuasive is a good fit? a comment on theory testing.

Psychological Review, 107

(2), 358-367.Slide47

Conclusions, speculations & suggestions (1/4)It is definitely not possible to infer back from additive factors to underlying architectures (or, more precisely, you need many additional – and possibly unexpected – assumptions to make this inference)30/07/09

Conclusions, speculations & suggestions (2/4)In the Stroop task, despite physical separation of the stimulus elements they are still bound by attention

i.e. locked inputs

30/07/09

Conclusions, speculations & suggestions (3/4)Despite optimality requirement that decision making be single stage, evidence for ‘additive factors’ in decision making is undeniable and is not negated by plausibility of continuous processing, PDP-style, conceptions of neural processes.

30/07/09

Conclusions, speculations & suggestions (4/4)Unlikely that ‘simple perceptual decision making’ is simple, even in paradigmatic cases such as the RDK30/07/09

what next?Show that presence/absence of attentional binding can make processing additive or interactive.Demonstrate

additivity

(i.e. non-optimality) in random dot

kinegrams

(properly)

30/07/09

Stafford, T., Gurney, K.N. & Ingram, L. (2009). Piéron’s

Law holds in conditions of response conflict. In N.A.

Taatgen

& H. van Rijn (Eds.),

Proceedings of the 31th Annual Conference of the Cognitive Science Society

. Cognitive Science Society.