Object and Scene Perception

• PSYCH 2B: Attendance should be logged on Moodle.
• Dr. David Simmons is located at 62 Hillhead St., Rm. 503.
• Contact Dr. Simmons:
• Tel: 0141 330 3612
• E-mail: [email protected]
• X: @DrDavidRSimmons
• Office hours are on Thursdays from 11am-1pm.
• The aims are to explain object and scene categorization principles and describe the physiology of object and scene perception.
• Sources: Yantis & Abrams (2017) pp. 113-153, Schwartz & Krantz (2024) Chapter 5 “Object Perception”.
• The visual system converts structured light patterns imaged on the retina into a perception of a solid three-dimensional world.
• A scene is a view of a real-world environment that contains background elements and multiple objects organized in a meaningful way.
• Scenes are acted within and objects are acted upon.
• Early experiments in monkeys point to the Inferotemporal Cortex (IT)'s importance.
• IT and its sub-regions TE and TEO are the endpoint of the "ventral" or "what" processing stream.
• Object coding appears to be distributed, according to most scientists.
• Consider "Jennifer Aniston" neurons.
• Gibsonian theory offers a different perspective on objects.
• Diagnosticity: Essential visual features that differentiate objects. This will be discussed further in the colour perception lecture.

Features

• Elementary features combine into extended contours and shapes using Gestalt rules.
• Gestalt grouping "rules" include:
• Proximity
• Similarity
• Good Continuation
• Simple cells contribute to perception by processing coarse features and fine details.
• V1 is invovled in contextual influences on local processing.
• Global grouping of contextual structure is related to V2.
• Large receptive fields are sensitive to low spatial frequencies.

Perceptual Segregation and Figure/Ground

• Perceptual segregation involves assigning different interpretations to different parts of a scene.
• A key step is segregating the figure from the background.
• This isn't always easy
• Evidence that observers can discriminate details more accurately in the foreground
• Illusory contours are inferred by the visual system even when the foreground object is not present, as seen in the Kanizca Triangle.

Object Categorization

• Levels of object categorization:
• Super-ordinate: It’s an animal
• Basic: It’s a dog
• Subordinate (Exemplar): It’s a Border Collie.
• There is debate about which level is quickest during categorization tasks.
• Viewpoint invariance vs. multiple views relates to how objects are encoded by the visual system.
• Encoding can be 3-D models and/or multiple "snapshots”

Scene Perception

• "Gist" refers to the general description of a scene.
• It is available after only a fraction of a second.
• Scene Gists can be related to Google Image Perception.
• Global Image Features (Torralba & Oliva) are used to get to the gist
• Degree of naturalness (natural vs. man-made)
• Degree of openness (visible horizon)
• Degree of roughness (linked to complexity)
• Degree of expansion (perspective cues)
• Color (characteristic of a given location)
• Assumptions are made about the identities of objects in scenes based on size and location, influenced by experience.
• Artists can play with these assumptions.
• Theorists suggest inferences or hypotheses are made about the world (Helmholtz, Gregory, Rock, Friston).
• This is the essence of indirect perception.
• Inferences can affect judgments, such as in superstitious perception.
• Cognitive Toponymy is the study of what place names say about how people conceptualize their environment.
• https://www.gla.ac.uk/schools/critical/newsandevents/archivedconferences

Temporal Cortex Structures

• fMRI experiments in humans have revealed more structures in the Temporal Cortex.
• FFA = Fusiform Face Area
• OFA = Occipital Face Area
• PPA = Parahippocampal Place Area
• EBA = Extra-Striate Body Area
• VWFA = Visual Word Form Area
• fMRI experiments suggest a similar arrangement in monkeys (Bell et al, 2009).
• LOC (Lateral Occipital Complex) and IT (InferoTemporal Cortex) have lots of overlapping sub-regions.