> Objects form categories because they share a number of features and
> differ on other features from contrasting categories. One essential
> function of a feature is therefore to subserve the categorization and
> representation of objects. The target article questioned the origin of
> features. Either people come equipped with a complete, fixed feature
> repertoire that accounts for all present and future categorizations,
(THIS IS UNLIKELY AS BABIES ARE NOT NECESSARILY AS ACCURATE AS ADULTS
IN CATAGORISATION, EG. THEY OFTEN CALL ANYTHING WITH FOUR LEGS ^A
> or they sometimes create flexible features to subserve new
IT IS PROBABLY BOTH: SIMPLE, INNATE REPERTOIRES (EG.
HOW TO TELL APART DIFFERENT COLOURS) MAY LATER BE SUPPLEMENTED BY THE
ABILITY TO CREATE NEW ONES; AS SEEN IN THE ^MARTIAN BLOBS EXPERIMENT^.
IT MAY BE INTERESTING TO SEE IF A SIMPLER VERSION OF THIS TECHNIQUE
COULD BE PRODUCED FOR USE WITH INFANTS EG. BY LOOKING AT THEIR GAZE,
DUMMY-SUCKING RATES ETC (TO SEE IF THIS TOO IS INNATE OR LEARNED VERY
EARLY). HOWEVER THIS WOULD BE VERY DIFFICULT AS THE TASK IS COMPLEX
AND BABIES CAN^T TELL US HOW THEY CATAGORISE THINGS, WE CAN ONLY
> The target article examined the implications of the latter view that
> flexible features are not necessarily derivable from a fixed set of
> primitives, can augment the representational power of the feature
> repertoire, and can change how an input is perceived.
> from the outset, it is important to emphasize that the flexible
> feature stance adheres to the reductionist enterprise of cognitive
> psychology which prescribes that complex object representations should
> be reducible to combinations of their building blocks.
YES IT DOES, BUT WHAT ABOUT THE HOLISTIC VIEW (EG. GESTALT). IN
EVERYDAY LIFE WE OBSERVE THAT OBJECTS ARE NOT SIMPLY A COMBINATION OF
FEATURES THAT ARE PROCESSED BOTTOM-UP. FOR EXAMPLE, HOW OUR BRAINS ARE
MISLED BY ILLUSIONS: OBJECTS APPEAR DIFFERENTLY ACCORDING TO THE
PERSON^S PAST EXPERIENCE, EXPECTATIONS ETC. NUMEROUS EXAMPLES PREVAIL:
EG. MULLER-LYER, NECKER CUBE, KANIZA TRIANGE, AND THAT GREAT ANNOYING
EXAMPLE OF WHEN YOU^RE ON A TRAIN AND YOU THINK YOUR TRAIN IS MOVING
WHEN IT ISN^T! (MOTION PARALLAX).
> The main alternative to the compositional view proposes that objects
> are represented holistically,without a prior decomposition into their
> components. For instance, Edelman discusses a system which learns the
> appearance of entire objects and uses their memory traces as holistic
> features. In a related vein, Burgund and Marsolek suggest that specific
> brain systems could be dedicated to the extraction of holistic features
> that represent familiar objects. Holistic representations have two main
> advantages over componential representations: (1) they preserve the
> input in an unprocessed form and (2) they efficiently represent the
> input by compressing multiple sources of information into a single
> feature. Holistic and componential representations can co-exist in the
> flexible feature framework. It is therefore an augmented
THIS VIEW IS VALID AND PROBABLY MORE REALISTIC, BUT MAKES IT MORE
DIFFICULT TO STUDY AND UNDERSTAND CATERGORISATION AS IT COMPLICATES
THINGS ( AS IN EVERY AREA OF PSYCHOLOGY FROM MENTAL ILLNESS TO
> As already discussed in section 1 of the target article,
> compositions of flexible features inherit all of the strengths of the
> classical mental chemistry of the fixed feature approach: Many object
> descriptions can be generated from a set of elements and a set of
> combination rules; feature combinations allow for structured
> hierarchical representations; similarity relations between different
> objects can be expressed in terms of their features and their
> combination rules.
YES, BUT THIS DOESN^T ALLOW SUCCESSSUL GENERATION OF ALL CATAGORY
MEMBERS AND MAY LEAD TO MISTAKES. SOME CATAGORY MEMBERS (THE NOTORIOUS
TOMATO) ARE MORE SIMILAR TO MEMBERS OF OTHER CATAGORIES THAN TO THEIR
OWN. FOR EXAMPLE, A TOMATO IS A FRUIT (DUE TO IT^S PIPS, I THINK!)
YET IS OFTEN CONFUSED WITH VEGETABLES AS IT DOESN^T GROW ON TREES
(LIKE MOST FRUIT), IS EATEN WITH SALAD ETC.
> R3.1 Chunking.
> Chunking and perceptual unitization (see 3.1.) were discussed in the
> target article as processes that could synthesize new features from a
> set of more elementary components. Chunking therefore implies that the
> input is segmented into features before being chunked--much in the way
> in which a capital T may be initially be discretized into a vertical
> and a horizontal bar before being chunked into a holistic T.
> Phenomenologically, the perception of the chunk does not entail the
> perception of its components. A chunk is therefore a new, isolatable
> and independent information packet of psychological processing that has
> the properties of holistic representations: The recognition of a chunk
> will not necessarily prime the recognition of its components, and vice
> versa; response times to the chunk will be faster than predicted by
> response times to the components (Goldstone, Steyvers, Spencer-Smith, &
> Kersten, in press); and similiarity relationships will not necessarily
> be perceived between the chunk and its parts.
> Good examples of chunking producing new features have recently been
> described in the category expertise literature. For example, Tanaka
> discusses the case of faces which are initially analyzed into their
> consituent parts (e.g., nose, mouth, eyes and ears) before being
> chunked into configural, holistic representations with the progressive
> acquisition of expertise in face categorization.
THIS APPEARS VALID AS IN EVERYDAY LIFE WE ARE QUICKER TO RECOGNISE
FACES WE KNOW IN THE STREET THE BETTER WE KNOW THE PERSON. WE APPEAR
TO BUILD UP HOLISTIC PROTOTYPES OF FACES WE KNOW WHICH AIDS PROCESSING.
HOWEVER, FEATURE PROCESSING IS STILL IMPORTANT UNDER SITUATIONS OF
AMBIGUITY (EG. WHEN PERSON IS WEARING SUNGLASSES THEY DON^T USUALLY
> R3.2 Feature creation: Form-from-medium rather than form-from-form.
> We want to distinguish the form of feature newness involved in chunking
> (which we call form-from-form) from another kind (form-from- medium)
> which directly produces features from a medium, not from other
> features. By analogy, imagine a Martian whose visual medium (the output
> of its transducers) is very much like dough. On the first day of its
> existence, the outside world imprints a teddy bear into the dough. Of
> course, this object and its parts are unknown to the Martian. He or she
> cannot compose a new representation of the modelled teddy bear from an
> already-existing representation of its component parts. Feature
> creation is a process which can directly imprint on the visual medium:
> It can cut around the teddy-bears silhouette and represent the entire
> object as a new holistic feature. Note that this cutting process only
> separates the entire bear from the medium. At this stage of conceptual
> development, our Martian represents the bear as a unitary, holistic
> feature and its decomposition into subcomponents is unspecified.
GOOD POINT, BUT THE ANALOGY OF AN ALIEN MAY BE MISLEADING- WE ARE MOST
LIKELY BORN WITH INNATE PRINCIPLES FOR BREAKING DOWN HOLISTIC OBJECTS,
ESPECIALLY HUMAN FACES, INTO SMALLER COMPONENTS! THIS HAS BEEN SHOWN
NUMEROUS TIMES IN INFANT STUDIES. AN ALIEN WOULD NOT HAVE THIS
ABILITY-OR IF IT DID IT MAY ONLY SUIT IT^S NEEDS ON THE HOME PLANET.
> R3.4 What is it like to be a feature?
> The discussion so far distinguished between chunking, imprinting and
> emergent perceptual properties as different forms of feature newness.
> These distinctions made implicit assumptions on what it is like to be a
> feature that we now highlight.
> Features are isolatable information packets. This first property
> stresses that features represent compressed information from the input
> to which the system is sensitive. This information can be parts (as
> suggested in Tanaka and Singh and Landau), but it is not limited to
> parts. Colored blobs, textural elements, and many other information
> packets can qualify as features as long as the systems psychogical
> response to the packet reveals that it is a discrete, holistic entity
> in psychological processing.
INDEED, A FEATURE CAN BE ANYTHING, FROM A PERSON TO PLANET EARTH TO THE
SOLAR SYSTEM TO THE GALAXY- IT DOESN^T MATTER AS LONG AS IT MAKES UP
> Features are independently perceived. Isolatable features share the
> property of being independently perceived. As
> opposed to feature conjunctions for which the perception of each
> component must precede the perception of the conjunct, isolatable
> features are perceived without such prior perceptions. Independently
> perceived features can evolve both from a chunking process which
> produces configural features, from an imprinting process which creates
> a new form from the visual medium, or from dimensionality reduction
YES, BUT MOST FEATURES ARE NOT PERCIEVED INDIVIDUALLY: THE FEATURE IN
IT^S ENTIRE CONTEXT NEEDS TO BE CONSIDERED; WHEN ISOLATED, A ^MOUTH^ IS
ONLY A WONKY LINE, YET WHEN ADDED UNDER TWO EYES AND A NOSE IT BECOMES
OUR WELL KNOWN MOUTH!
> R4.1 Does feature creation require more flexibility?
> Continuous versus discrete feature learning in time. One possible
> interpretation of our proposal is that features created to solve a
> categorization subsequently crystallize and become fixed. To this,
> several commentators objected that we should instill more flexibility
> in the feature repertoire (Hahn & Chater; Tanaka; Williams, Gauthier &
> Tarr) because feature creation and adaptation is a never ending
> We agree with the idea that the feature repertoire should continuously
> evolve in response to the flux of new categorizations facing the
> organism. One extreme view suggests that every encounter with the
> objects of a class could lead to a small amount of feature-space
> reorganization (Williams, Gauthier & Tarr; Hahn and Chater). The issue
> of continuous variability raises an important problem that was not
> discussed in the target article: How does the system store information
> about feature variations?
YES, AND HOW DOES IT HAVE THE ROOM!
> One possibility is that each time the system sees an object, it would
> replace its old feature representation with the representation of the
> new features.
ECONOMICALLY MORE VALID
> However, such system is liable to catastrophic forgetting. Successive
> exposures to rare instances of a feature could lead to a transformation
> of the feature that would not match common instances anymore. Another
> possibility for representing variations is to apply the template
> matching approach to features and store each transformation as a
> distinct feature exemplar in memory. However, given all the variations
> in illumination conditions, pose and occlusion that features can take,
> exemplar-based systems would rapidly be overwhelmed with the millions
> of feature exemplars it would need to store and organize.
YES, BUT EXEMPLARS DON^T NEED TO BE THAT SPECIFIC. FOR EXAMPLE, AN
EXEMPLAR OF A MINI (EG. ROUNDED BODY, SMALL, MINI LOGO, SMALL ROUND
HEADLIGHTS ETC..I^M NO EXPERT ON MINIS!) ALLOWS US TO RECOGNISE MOST
MINIS (EG. IN MOST ILLUMINATIONS, SITUATIONS ETC). WE WOULDN^T
NECESSARILY NEED AN EXEMPLAR FOR EVERY DIFFERENT TYPE OF MINI IF THEY
SHARE ENOUGH BROAD FEATURES (WHICH THEY GENERALLY DO).
> Thus, we favor an abstract representation (for parts, think, e.g., of a
> parametrized elastic template) which would very slowly adjust to local
> feature transformations to preserve a desirable inertia in the
> continuous adaptation to changes. The next section discusses how this
> might occur.
Darling, Andrea email@example.com
This archive was generated by hypermail 2b30 : Tue Feb 13 2001 - 16:23:20 GMT