This is the slides for the 3rd presentation in my PSY 637 Human Information Processing class.

1. A Feature-Integration
Theory of Attntion
Anne Treisman & Garry Gelade (1980)
Jing Chen

2. 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

3. 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”

4. 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.

5. 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

6. Disjunction Target
Find the blue letter
• Easy: • Just as Easy:
X T X T T T X T
X T X T
X T X X T X T T
X T T X
T X T T X X T X
T X X X
X X T X T X T X
T T X T
T X T T X T X T

7. Conjunction Target
Find the green “T”
• Hard: • Even Harder:
X T X T X T X T T T X T
X T T X X T X X T X T T
T X X X T X X T X T T X
X X T X T X T X
T T X T
T X T T X T X T

8. 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;

9. 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.

10. 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.

11. 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).

12. 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.

13. 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.

14. 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.

15. Experiment 3: Results
• The pattern of results is quite
“Central”
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.

16. 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

17. 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

18. 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).

19. 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).

20. 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
OOVOO
VOVVV
VOVOV The task was to sort the packs of cards into two
OOVVO piles, one containing cards with a horizontal and one
OVVOV with a vertical boundary.

21. Experiment 5: Results
• The difference between the two feature packs and
the conjunction pack was qualitative and obvious.
Face-up Face-down
• The color condition: OV|OV 15.9 25.1
• The shape condition: OO|VV 16.2 25.6
• The conjunction condition: OV|OV 24.4 35.2
•
• Suggesting that the boundary cannot be directly
perceived in the conjunction condition and has to be
inferred from attentive scanning.

22. 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.

23. 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)
Again, what matters is
• The conjunction conditions: whether the boundary is
• PQ/RO (978 ms) defined by a single feature or
• FK/EX (1114 ms) a conjunction of feature

24. 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.

25. 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
OXOXOO
• Dependent variable: OXOXHX
• accuracy with brief exposures

26. 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).

27. 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.