the feature-integration of attention_jing
DESCRIPTION
This is the slides for the 3rd presentation in my PSY 637 Human Information Processing class.TRANSCRIPT
A Feature-Integration Theory of Attntion
Anne Treisman & Garry Gelade (1980)
Jing Chen
Outline
• The Feature-Integration Theory of Attention
• Paradigms/Experiments• Visual search (Exps 1, 2, &3)
• Illusory conjunctions (Exp 4)
• Texture segregation (Exp 5, 6, & 7)
• Identity and location (Exp 8 & 9)
• Conclusion
The Feature-Integration Theory of Attention
• Features are registered early, automatically, and in parallel across the visual field, while objects are identified separately and only at a later stage, which requires focused attention to “glue” features together.
• Attention is necessary for the correct perception of conjunctions, although unattended features are also conjoined prior to conscious perception. • “Illusory conjunctions”
Dimension vs. Feature
• “Dimension” refers to the complete range of variation
• “Feature” refers to a particular value on a dimension
• Thus color and orientation are dimensions; red and vertical are features on those dimensions.
Experiment 1: Visual Search
• Purpose: • To compare search for disjunction targets and
conjunction targets;
• To explore the effect of extended practice on serial and parallel search;
• Among the distractors Tbrown and Xgreen
• Disjunction targets: a blue letter or an S;
• Conjunction targets: Tgreen;
• Setsize: 1, 5, 15, and 30
Disjunction Target
Find the blue letter
• Easy:
X T X T
X T T X
T X X X
T T X T
• Just as Easy: X T X T T T X T X T X X T X T T T X T T X X T X X X T X T X T X T X T T X T X T
Conjunction Target
Find the green “T”
• Hard:
X T X T
X T T X
T X X X
T T X T
• Even Harder: X T X T T T X T X T X X T X T T T X X T X T T X X X T X T X T X T X T T X T X T
Experiment 1: Results
• Conjunction: search time increased linearly
with setsize; search is serial and self-
terminating;• Disjunction: for positive displays, search times
were hardly affected by setsize; for negative
displays, the relationship is linear;
Experiment 1: Results
• The effect of extended practice:
• There is little indication of any
change in the pattern of results;
• no sign of a switch from serial to
parallel search.
Experiment 1: Discussion
• Focal attention, scanning successive locations serially, is the means by which the correct integration of features is ensured.
• When this integration is not required by the task, parallel detection of features should be possible.
Experiment 2: Visual Search
• Purpose: to explore the relation between the discriminability of the features of a conjunction and the speed (slop) of detecting that conjunction as a target.• Compare • Difficult condition: a conjunction target in distractors
similar to it (T in X and T);
• Easy condition: distractors differed maximally from the target (O in O and N).
Experiment 2: Results
• The slopes in the difficult
discrimination are nearly three times
larger than those in the easy
discrimination
• but the linearity and the 1/2 slope
ratio is preserved across these
large differences.
Experiment 2: Discussion
• The search rates vary dramatically for easy and difficult conditions.
• In both easy and difficult conditions for the conjunction targets, the search were serial, self-terminating.
• As a result, we cannot say that search becaomes serial only when it is difficult.
Experiment 3: Visual Search
• Purpose: to explore an alternative explanation for the difference between conjunction and disjunction targets.• attributes the difficulty of the conjunction condition to
the centrality of the target in the set of distracters.
• Replicate this aspect of the similarity by using unidimensional stimuli, with no need for checking conjunctions.
Experiment 3: Results
“Central”• The pattern of results is quite
different from that obtained
with the color-shape
conjunctions and disjunctive
features.
• When the intermediate target
is present, its detection doesn’t
depend on a serial check of
the distractor, which the
detection of the conjunction
did.
Experiment 4: Letter Search
• Purpose: to discover whether integrative attention is required even with highly familiar stimuli, e.g., letters
• Confusability of letters• Letters would be difficult to search when they are
similar in a wholistic way.• R/PB
• Sets of letters would be confusable if their features were interchangeable and could potentially lead to illusory conjunctions. • R/PQ
Experiment 4: Letter Search
• Purpose: to discover whether integrative attention is required even with highly familiar stimuli, e.g., letters
• The conjunction condition (with interchangeable features): R/PQ and T/IZ
• The similarity condition (with greater target/distractor similarity): R/PB and T/IY
Experiment 4: Results
• The ratio of positive to negative
slopes differed for the
conjunction and the similarity
conditions:
• For the conjunctions, it was
0.45, which is close to half
and suggests a serial self-
terminating search.
• For the similarity condition,
it was much lower (0.26).
Experiment 4: Discussion
• Letter search would be serial and self-terminating if the particular sets of distractor and target letters were composed of perceptually separable features which could be wrongly recombined to yield conjunction errors.
• Otherwise search could be parallel (although not necessarily with unlimited capacity and no interference).
Experiment 5: Texture Segregation
• Purpose: to investigates the “preattentive” segregation of groups and textures, which could guide the subsequent direction of attention.
• Five rows * five columns; card sorting task:• The color condition: OV|OV
• The shape condition: OO|VV
• The conjunction condition: OV|OV
OOVOOVOVVVVOVOVOOVVOOVVOV
The task was to sort the packs of cards into two piles, one containing cards with a horizontal and one with a vertical boundary.
Experiment 5: Results
• The difference between the two feature packs and the conjunction pack was qualitative and obvious.
• The color condition: OV|OV
• The shape condition: OO|VV
• The conjunction condition: OV|OV
•
• Suggesting that the boundary cannot be directly perceived in the conjunction condition and has to be inferred from attentive scanning.
Face-up Face-down
15.9 25.1
16.2 25.6
24.4 35.2
Experiment 6: Texture Segregation
• Purpose: to discover whether the advantage of the feature boundary was due to• In the feature pack, only one dimension was relevant
• But the conjunction pack, require attention to both dimensions.
• Change the feature display into multiple-dimensional one: OΠ|OV (26.9 vs. 32.9 sec)
• Results:• The disjunctive features appear slightly less effective than single
features.
• The relevance of two dimensions rather than a single dimension can explain only a small fraction of the difference between features and conjunctions.
Experiment 7: Texture Segregation
• Purpose: to see whether the distinction between features and conjunctions is equally crucial when the features are local components of more complex shapes rather than values on different dimensions (as in 5&6).
• The single feature conditions (short diagonal line): • PO/RQ (779 ms)
• EO/FQ (799 ms)
• The conjunction conditions:• PQ/RO (978 ms)
• FK/EX (1114 ms)
Again, what matters is
whether the boundary is
defined by a single feature or
a conjunction of feature
Experiments 8&9: Spatial Location
• Purpose: to test whether precise information about spatial location is available at the feature level, • by looking at the dependency between reports of
identity and reports of location on each trial.
• Difference between Exps 8 & 9:• In Exp 8, the presentation times of the arrays were
chosen to make sure the accuracy in each condition was 80%.
• In Exp 9, equal presentation times were used for features and conjunctions.
Experiments 8&9: Spatial Location
• All distractors were OX
• The targets:
• The disjunctive feature condition: H, H, X, or O
• The conjunction condition: X or O
• Dependent variable:• accuracy with brief exposures
OXOXOOOXOXHX
Experiments 8&9: Results
The conditional probabilities follow a very similar pattern.It seems likely that in order to focus attention on an item, we must spatially localize it and direct attention to its location.Feature localization is a special kind of conjunction task (feature and spatial location).
Conclusions
• All the data taken together support the feature-integration theory of attention.
• Separable features can be detected and identified in a early, parallel process;
• this process mediates texture segregation;
• locating any individual feature requires an additional operation;
• conjunctions of features require focal attention to be directed serially.