Method: Reaction Time (RT)

• Example:– Simple detection ($, ruler, glasses)

• Liberal vs. conservative response criterion• (speed/accuracy trade-off)• Secondary task• Additive method (e.g., visual degradation)

Subtractive Method

• Task 1: simple detection task – press key when light blue appears on the screen

• Task 2: discrimination task– Respond to the blue light but not to the yellow light

• The two tasks have:– Same stimulus (blue light)– Same response (key press)– Only one thing different (?): discrimination vs. detection

• RT discrimination - RT detection = the mental operation of having to discriminate two stimuli

Subtractive Method

• Very simple and powerful method• Developed by Donders in the 1800’s• Used even today (e.g., fMRI studies)• But it has its problems

– What constitute the elemental mental operation– It is not very flexible

Additive Factors Method• Developed by Sternberg (1969)• Example: memory task (as already described)

• Numbers were displayed 3 9 5 4• Delay• A probe 4 ‘yes’

• Number of items in each trial vary from 1 to 6 items

3 7 9 2

9

Another trial

5 1

1

Plot:

- RT relative to number of items in the list

- plot separately ‘yes’ and ‘no’ trials

Stages: Encode target Search in WM Select response Start response

INPUT OUTPUT

Factors target visibility number of items target probability ease of response

Additive factors

• Assumes serial processing of stages• Often this is not the case

– E.g., addition

– RT to decide 4 + 3 = 12 ‘no’– RT to decide 4 + 3 = 11 ‘no’– Because addition and multiplication are run in parallel

– But, does this mean a single system?

On Method: Dual task

• Tasks that tap onto the same system interfere with each other– Having your room-mate talk to you when you are trying

to remember a phone number (phonological code)

• No interference = independent systems

STM

STM

STM

STM

One STM ….. Or many?

. . .

Short-Term Memory for Visual andVerbal Materials: One or two stores?

Approach 1: Store maximum capacityof one type -- then see if person can remember any of the other type.

3 9 8 2 1 7 4 +Example:

4 9 3 2 6 8 7

?

One more time...

7 4 1 2 3 9 8

?

How did you do??

Usual Finding:

ZERO interference between verbaland visual STM loads

- different memory systems are involved in the short term retention of objects and verbal stimuli…

- This result is difficult to interpret without reference to mental representations.

- Thus, we infer the existence multiple memory buffers, (a type of mental representations)

Question for thought

• If your data shows interference, can you still rescue the idea of independence between visual and verbal short-term memory?

• hint: itemize step-by-step what you did, making sure to not skip any steps (think of it as a writing computer code for a a machine to compute the task, do not make any pragmatic assumptions of knowledge).

Mental Representations: 3 Levels of Analysis

(1) Computational: What is the problem to be solved? (i.e. input/output mapping of the mental process)

(2) Algorithmic: How is this calculation carried out?

(3) Implementational: What is the hardware that makes these calculations possible?

Question for debate

• Does neuroscience (level 3) help for understanding psychology (i.e., how mental processes are carried out in level 2)?– Yes:

• Reductionism; eliminativism • cognitive neuroscience,

– No: • functionalism, Marr (think birds and planes)• dualism

Cognitive Psychology:

The study of the structures, and processes ofthe mind and brain that take in, transform, and use information.

But what do we mean by “information?”

Types of Information (Mental Representations)

Sensory information:- Images on our sensory organs, coming from light of a particular frequency that stimulates the rods and cones in our retinas

Conscious Perception:that are stored in and manipulated by our minds (e.g., of color, sound, etc.)

Other types of mental representation (memories):

Procedural knowledge (“knowing how”): e.g. how to throw a frisbee, swing a golf club, drive a car…In other words, skill knowledge, or knowledge that doesn’t refer to the state of things in the world.

Declarative knowledge (“knowing that”):

(2) Episodic knowledge: knowledge about the worldthat is specific to a particular time and place. E.g. What’s the last song you heard on the radio? What time did you wake up this morning? Where were you last New Year’s Eve?

(1) Semantic knowledge (referred to asgeneric knowledge in your textbook) refers to facts about the world. E.g. what color is the sky?, what is 7x9?, who is the quarterback for the Ducks?

Cognitive Psychology:

The study of the structures, and processes ofthe mind and brain that take in, transform, and use information.

But what do we mean by “processes?”