A summary of lecture notes on object recognition, along with practice questions to help students better understand and test their knowledge on the concept. The note includes theories such as RBC, template, and functional.
Lecture 05 - Object Recognition
🧠
The challenge of object recognition:linking currentexperience w/ past experience(memory)
Theories
🧠
template theory:recognizing objects as a whole ratherthan breaking it down into the parts that
make it up
○ template: a memorized notion of something you’ve seenbefore
○ when you see an object you align it to the template
○ consistencyis key for this theory
○ requires you to havea template for every single thingyou’ve seen in life, in every possible
orientation/angle you’ve seen it in
■ that’s a lot of fucking brain space
■ as we learn, new templates are created
○ barcode anecdote
■ a particular barcode is associated w/ a particular item in the entire store, likewise a
particular item in a particular orientation matches up with one of the million templates
in your mind
○ the problemw/ this theory is that itassumes thebrain is 10x largerthan it actually is,cause
🧠CAPTCHAexplained throughtemplate theory
○ bots have difficulty computing the CAPTCHA tasks because they don’t align with any
templates the technology has
○ gatekeepers bots from buying T-Swift tickets (except they’re becoming more advanced and
learning from humans completing the CAPTCHAs to bypass it
🧠feature analysis theories:recognizing an object bybreaking it down into the partsthat make it up
○ an object is made up of a particular arrangement of features [lines, shapes, etc.]
➔ The “T” is comprised of particular featuresthat
are stored in our minds as mental representations,
when we notice those features together we realize
we’re looking at a “T”
🧠recognition by components (RBC):recognizing an objectby its 3D components (referred to as
geons)
○ think of it as the“lego theory”,geons = buildingblocks that can be combined to make sets
○ states we have various geons in our minds thatdifferin terms of shape[contour, number of
connection points, symmetry, size, etc.]
○ differs from feature analysis theoryas it looks ata 3D shape rather than the features that would
make up a shape [i.e. lines]
, ○ differs from template theorybecause you don’t need to have a geon in diff angles to recognize
the objects
■ Biederman (theory developer) states, however, that you would need to see all the geons
of the object in order to recognize it
○ alimitationto the theory is that it accounts forshape and orientation of the geons, but
doesn’t necessarily account for other physical properties that can differentiate objects from
each other [texture, colour, etc.]
🧠all theories have different viewpoints on whether or not the perspective in which the object is viewed
matters
○ view-dependent:orientationmattersin order to recognizean object
■ i.e.template theory
○ view-invariant:orientationdoes notmatterin orderto recognize an object
■ i.e.RBC theory
🧠repetition suppression (RS):brain activity decreaseswhen your brain gets used to looking at a
stimuli
○ repetition:repeated exposure
○ suppression:reduction in brain activity
○ this phenomenon was discovered shortly after the development of fMRI
○ to observe this phenomenon, you would use the subtraction method
■ [neural activity for 1st presentation] - [neural activity for 2nd presentation]
● present a stimulus for the first time, note the brain areas that activate [i.e.
attention, visual perception, etc.]
● take the stimulus away for a bit
● present the stimulus again and take note on the activated brain areas
○ you’ll notice that there would be less areas active since your brain is
getting used to the stimulus and has a better mental picture of it
○ this reduction in brain activitydoesn’t hinder recognitionability, rather is more about the
brain beingmore efficientwhen it recognizes objects
○ hypothesis: each time you see a stimulus the brainfine tunes the features that make up the
object, filters out unnecessary features [i.e. the colour of an umbrella not an important
defining feature of umbrella]
○ this theory can work for any visual stimulus [i.e. faces]
■ thebrain recalibrates when there’s a dramatic change[Kaaviya w/ straight blue hair]
🧠the fusiform area located in the temporal lobe is known for object recognition
🧠using RS to test out if perspective of an object’s orientation matters
○ fusiform area in the left hemisphere = view-invariant
○ fusiform area in the right hemisphere = view-dependent
○ ergo, the brain isboth view-invariant and view-dependent,depending on the side of brain
you’re looking at
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