subtractive methodology Donders’ subtractive methodology

IAAF policies consider that there is a limit to how fast a human can react to a start signal. As of 2002, if an athlete left the blocks sooner than 100 ms. after the start signal, he was deemed to have false-started. Some fans think this is wrong and that any reaction after the gun should be allowed. The best athletes reaction times are usually in the range of 120 mSec (0.12 sec) to 160 mSec. Tim Montgomery improved that to a near perfect 104 mSec - and came very very close to being false-started. The only sprinter to get closer to perfection was Surin Bruny - who managed a 101 mSec in a the 1999 WC 2nd semi-final. Burrell's 1991 world record began with a reaction time of just 117 mSec. In the same race, Carl Lewis reacted in a snail's-pace 166 mSec, probably because he'd deliberately slowed his start due to having an earlier false-start posted against him (this put him at risk of disqualification if he false-started again). Taking away reaction time, Burrell covered the 100 metres in 9.783 seconds, Lewis in 9.764. Lewis was actually the faster runner, but Burrell was the better "gunner".

Mental Chronometry Subtractive Methodology

SIMPLE REACTION TIME (RT) TASK STIMULUS DETECTION RESPONSE EXECUTION

A simple reaction: There is only one response to a single stimulus. For example, a light goes on and the instruction is to press a key or a button as soon as possible after the onset of the stimulus. For Donders, this simple RT task (we will call it Task A) could be used as a baseline.

SIMPLE REACTION TIME (RT) TASK STIMULUS DETECTION RESPONSE EXECUTION

CHOICE REACTION TIME (RT) TASK

GO/NO GO REACTION TIME (RT) TASK

Simple RT Choice RT Go/Nogo RT Choice RT - Simple RT = Choice RT - Go/Nogo RT =

A problem with the Go/NoGo task

Go Respond to Circle but not a Square

NoGo What happens if the subject occasionally responds to the square? Donders: If this happens once, the whole series must be rejected: for, how can we be sure that when they had to make the response and did make it, they had properly waited until they should have discriminated

If the subject responded incorrectly “Go” to the square, maybe he or she also sometimes responded correctly to the circle without allowing enough time to identify it. A kind of “false start”. How can we be sure that when they had to make the response and did make it, they had properly waited until they should have discriminated. The subject may simply have responded correctly without waiting to determine if the target is a circle or a square. Go

In other words, the participant may have changed the amount of time he or she allows before responding to the target in the go/nogo task, triggering on some trials very fast anticipatory responses before the stage of identification has been completed. If this were true, the components involved in Task C are not just those which determine performance in Task B minus the added stage of response selection.

???????? Go/NoGo Choice RT The subtraction: Choice RT-Go/NoGo RT may not provide a valid measure of

Donders’ method is based on three assumptions. First, it is assumed that the mental processes of stimulus detection, stimulus identification, response selection and response execution are arranged sequentially, in the sense that the output of one serves as the input to the next. Second, it is assumed that only one process can be active at each moment in time between stimulus input and response output. Third, it is assumed that a mental process can be added or omitted without affecting the duration of the other processes, the so-called assumption of pure insertion.

The Word Superiority Effect Skilled readers are faster to identify any letter in a word than a single letter in isolation. e.g. HAND vs ###D

Cattell HAND ###D ###D HAND

A modern idea

Bottom-up Feed- forward Words Letters Features Excitatory Inhibitory

K on its own is quite confusable with R. K in WORK is more confusable with D than R WORK

The logic of additive factors What is a factor? Any type of stimulus or response can be varied in some systematic way. We can make letters small or big BIG SMALL We can make words familiar or less familiar BOOK ROOK We can make shapes easy to see or harder to see

The logic of additive factors Each of these properties of the stimulus (we can do the same for responses) is termed a factor or variable if we wish to make use of it in an experiment. We can make letters small or big BIG SMALL Size We can make words familiar or less familiar BOOK ROOK Familiarity We can make shapes easy to see or harder to see Stimulus Quality

Why might we want to vary a stimulus or response factor? Stimulus Identification Response Selection Response Execution

Why might we want to vary a stimulus or response factor? Easy vs Hard to See is a Factor (Variable) that affects Stimulus Identification Stimulus Identification Response Selection Response Execution

Response Selection. Respond with the hand on the same side as the target object Compatible Mapping

Response Selection. Respond with the hand on the opposite side to the target object Incompatible Mapping

Why might we want to vary a stimulus or response factor? Easy vs Hard to See is a Factor (Variable) that affects Stimulus Identification Compatible vs Incompatible Mapping is a Factor (Variable) that affects Response Selection Stimulus Identification Response Selection Response Execution

Why might we want to vary a stimulus or response factor? Easy vs Hard to See is a Factor (Variable) that affects Stimulus Identification Compatible vs Incompatible Mapping is a Factor (Variable) that affects Response Selection Stimulus Identification Response Selection Response Execution Varying difficulty Varying difficulty

Examples of Compatible versus Incompatible Response Mappings. Respond with your left hand to Respond with your right hand to Incompatible response mapping Respond with your left hand to Respond with your right hand to Compatible response mapping Say white to Say black to Incompatible response mapping

Task: Respond to the direction of an arrow using a spatially corresponding keypress. Right

Task: Respond to the direction of an arrow using a spatially corresponding keypress. Left

Task: Respond to the direction of an arrow using a spatially corresponding keypress. Hard to See Left

Task: Respond to the direction of an arrow using a spatially corresponding keypress. Hard to See Right

Compatible versus Incompatible Response Mappings?

Compatible versus Incompatible Response Mappings? Task: Respond to the direction of an arrow using a spatially opposite keypress. Incompatible Mapping Left

Compatible versus Incompatible Response Mappings? Task: Respond to the direction of an arrow using a spatially opposite keypress. Incompatible Mapping Right

Compatible versus Incompatible Response Mappings? Task: Respond to the direction of an arrow using a spatially opposite keypress. Incompatible Mapping Hard to see Left

Compatible versus Incompatible Response Mappings? Task: Respond to the direction of an arrow using a spatially opposite keypress. Incompatible Mapping Hard to see Right

The Factors: Easy vs Hard to See and Compatible vs Incompatible have statistically independent effects on RT EASY TO SEE HARD TO SEE RT 500MS 550 MS 600 MS COMPATIBLE RESPONSE INCOMPATIBLE RESPONSE 650 MS ADDITIVE EFFECTS

Easy vs Hard to See Compatible vs Incompatible Responses Stimulus Identification Response Selection Response Execution Easy vs Hard to See Compatible vs Incompatible Responses

Letter Identification Orthographic Lexicon Phonological Lexicon SPEECH OUTPUT PRINT Grapheme- phoneme conversion rules Semantic System ?????

Letter Identification Orthographic Lexicon Phonological Lexicon SPEECH OUTPUT PRINT Grapheme- phoneme conversion rules Semantic System A factor affecting Letter Identification?

Letter Identification Orthographic Lexicon Phonological Lexicon SPEECH OUTPUT PRINT Grapheme- phoneme conversion rules Semantic System A factor affecting Letter Identification? Easy versus Hard to See Pencil vs Pencil

Letter Identification Orthographic Lexicon Phonological Lexicon SPEECH OUTPUT PRINT Grapheme- phoneme conversion rules Semantic System A factor affecting the Orthographic Lexicon (i.e. the speed of lexical access)?

Letter Identification Orthographic Lexicon Phonological Lexicon SPEECH OUTPUT PRINT Grapheme- phoneme conversion rules Semantic System A factor affecting the Orthographic Lexicon (i.e. the speed of lexical access)? High Familiar vs Low Familiar Words (Familiarity)

Examples Familiarity Familiar Words: HAND, BOOK, TREE, LIFE Less Familiar Words: PLUM, ROOK, SNIP, HIVE Easy to see: HAND FAMILIAR Hard to see: HAND Easy to see: PLUM LESS FAMILIAR Hard to see: PLUM

Task: Name the word as quickly and as accurately as possible.

The Factors: Easy vs Hard to See and Familiar vs Less Familiar Words do not have statistically independent effects on RT EASY TO SEE HARD TO SEE RT 500MS 550 MS 600 MS FAMILIAR WORDS LESS FAMILIAR WORDS 650 MS naming latency INTERACTIVE EFFECTS

Letter Identification Orthographic Lexicon Letter Identification Orthographic Lexicon