Week 8 Cognitive Visual Imagery

Visual Imagery

Visual imagery is information which passes through the

brain as though something is being perceived, when nothing

is actually happening. Someone may experience sight, smell,

sound, and touch as a result of visual imagery when none of

these stimuli are present. Visual imagery involve the use of

mnemonics

Mnemonics and mental codes

Mnemonics involve the construction of mental pictures or images

which helps us in increasing our chances of remembering

information. There are several techniques of mnemonics.

1) Method of Loci – requires the learner to imagine a series of

places (locations) that have some sort of order to them.

e.g., suppose you want to remember a list of 10 item to shop.

Technique of interacting images

states that recall of

concrete nouns on a list improved when participants will told

to form images of the words, in comparison to when they

were not given such instructions.

e.g., In a pair word recall test of the pairs dog/pipe, image of

a dog smoking pipe will make better recall than the images of

dog and pipe kept together

Peg word method –

it involves picturing the item with another

set of ordered “cues” – pegging them on the cue. In this case the

cues are not locations but rather nouns that come from a

memorized rhyming list.

The Dual – Coding Hypothesis

Alan Paivio (1969, 71, 83) originated the dual-coding

hypothesis of memory, According to Paivio

LTM contains two distinct coding systems (or codes) for

representing information to be stored. One is verbal,

containing information about an item’s abstract, linguistic

meaning. The other involves imagery: mental pictures of

some sort that represents what the items look like. Paivio’s

idea is that pictures and concrete words give rise to both

verbal labels and visual images.

The Relational – Organizational Hypothesis

Bower (1970b) proposed the relational-organizational

hypothesis.

The theory states that imagery improved memory, not

because images are necessarily richer than verbal labels, but

because imagery produces more associations between the

item to be recalled.

Forming an image typically requires a person to create a

number of links or hooks between the information to

remember and other information.

Bower (1970) experiment to distinguish dual coding

hypothesis from the relational organizational

hypothesis

Evidences for the existence of Imagery

Studies by Lee Brooks (1968) yield some of the best

evidence that images are distinct from verbal materials or at

least use different process from those used by verbal

materials

Mental Rotation of Images

by rotating them in their minds. This process demonstrates that mental rotation involves spatial reasoning and can be measured in terms of reaction time.

One important finding for visual imagery was that people

can do more than simply create images mentally, they could

also mentally transform them

Shepard & Matzler (1971) Experiement

Shepard & Matzler (1971) in their experiments showed

participants line drawings of three dimensional object. On each

trial subjects would see two drawings

1) same object with one rotated by some degree

2) mirror image reversals with/without rotation

The result of the experiment showed that the amount of time it

took participants to decide if the two drawings depicted the

same object or a mirror-image reversal was directly

proportional to the angle of rotation between the drawings.

The close relation between the angle of rotation of the

drawings and participants reaction times strongly suggest that

they performed the task by mental rotation of the drawing

Another Question

Another question that puzzled researchers was – whether

people mentally rotate the whole/part of the image in the

mental rotation task. Lynn & Cooper (1975) using the

irregular polygon task reaction time increased linearly with

the angle of rotation and the rate of rotation was same for all

the polygons regardless of their complexity.

In another study Cooper (1976) showed that mental

rotations like physical rotations are continuous in

nature

Cognitive psychologists also started searching how people

recognize objects presented in unusual angle. One possibility

is to mentally rotate the image till it reaches the orientation of

depiction (Pinker & Tarr 1989) or that distinctive geons of the

object remain visible we can recognize them with rotation

(Biederman & Gerhardestein, 1993)

The Nature of Mental Imagery

Visual images share some properties with pictures. But what

are images, what kind of properties do images have and how

are these like and unlike the properties that real pictures have?

Ronald Finke (1989) proposed some fundamental principles

of visual imagery. They are

1) Implicit Encoding: Mental imagery is instrumental in

retrieving information about the physical properties of objects or

about physical relationships among objects that was not

explicitly encoded at previous time

2) Perceptual Equivalence: Imagery is functionally equivalent to

perception to the extent that similar mechanisms in the visual system

are activated when objects or events are imagined as when the

same objects or events are actually perceived. (e.g. Perky 1910)

3) Spatial Equivalence: The spatial arrangement of the elements of a

mental image corresponds to the way objects or their parts are

arranged on actual physical surface or in an actual physical space

(e.g., Kosslyn, 1978)

4) Transformational Equivalence: Imagined transformations

and physical transformations exhibit corresponding dynamic

characteristic and are governed by the same laws of motion

(e.g., Cooper, 1976)

5) Structural Equivalence: The structure of mental images

correspond to that of actual perceived objects, in the sense

that the structure is coherent, well organized, and can be

recognized and reinterpreted (e.g., Kosslyn, Farah & Fliegel

1983)

Critiques of Mental Imagery

There exists many critiques to mental imagery. Some of

the main themes of debate are

1) Tacit knowledge & demand characteristics

2) Picture metaphor

3) Propositional theory

Tacit Knowledge and demand characteristics

Pylyshyn (1981) argued that the result from many imagery

studies reflect participants underlying and implicit, tacit

knowledge, and beliefs about the task rather than their

construction and manipulation of visual images.

Finke (1989) with his example of moving the coffee cup

provided evidence to Pylyshyn’s claim

Pylyshyn (1981) states that tasks that are affected by people’s beliefs

and expectations are termed cognitive penetrable. Such tasks make

it obvious to participants how they ought to perform and are said to

have demand characteristics (Orne, 1962)

Sometimes experimenters unconsciously give subtle cues to

participants. Intons & Peterson (1983) called such cues as

experimenter expectancy effects.

The Picture Metaphor

Visual images are casually spoken as mental pictures, how

far is the statement true. Pylyshyn (1973) pointed out that

pictures and images differ in several ways

1) Pictures can be physically looked at without knowing what

it’s a picture of but images cannot be looked at unless you

know what it is

2) Pictures and images are disrupted & disruptable in

different ways

3) Images are more easily distorted by the viewers

interpretation

Propositional Theory

Propositional Theory – original mental imagery idea is that

mental images are a special type of encoding;

propositional theory says this is not true, that there is only

one kind of encoding, which is neither visual nor verbal.

Pylyshyn suggested that the experience of having a

mental image is really just an epiphenomenon (something

that happens with a process, but that does not cause the

process, instead is just a by-product – without the epiphen.

The process would go on just like normal – not necessary for

process to occur)

Ex. when computer is calculating something, it often has a

flashing light, but flashing light has nothing to do with the

actual computation; if light blew out, computation will still

happen, so trying to understand how and why the light

comes on and flashes will not tell us anything about how the

computations are occurring

Instead, the encoding is propositional – concepts are stored

as symbols, and what is stored is not a physical

relationship, but a conceptual one, like the network models

of memory

So it would make sense that trying to scan a path from the

flag at the back of the boat to the cabin would take less

time than scanning from the flag to the emblem, since you

would have more nodes to go thru (2 vs. 4)

So it is possible to explain scanning times without having to

use a mental image

Spatial cognition

•Space of the body: Where are the parts of your

body located at any particular time?

•Space around the body: the area immediately

around you

•Space of navigation: larger spaces that we walk

through, travel to, and explore

•Our mental representations of these spaces may be

distorted, made “neater,” and more regular.