Olfactory bulb receives input from olfactory receptors which contact mucus in nasal cavity Smell

There are thousands of different receptors for different kinds of molecules Smell

Pheromones are not smells Pheromones are chemical signals sent from one animal to another Pheromones

Pheromones either induce a behavior in another animal or cause some physiological change Very common in insects...not so common in mammals...unclear role in humans Pheromones

For example: Androstenone, found in male pig saliva, causes a female pig to allow the male to mate with her Fun Facts about Pheromones

androstenone is also found in the sweat of human males! Does androstenone (or pheromones in general) affect humans? Design an (ethical) experiment… Fun Facts about Pheromones

Kirk-Smith & Booth (1980) sprayed some of the seats in a dentist’s waiting room with androstenone Compared to a control condition, more women used the androstenone seat Fun Facts about Pheromones

Fewer men used the androstenone seat ! Fun Facts about Pheromones

Other possible ways in which pheromones influence humans: – synchronization of menstrual cycles – mate selection - attraction to opposite major histocompatibility complex Pheromones

Pheromones do not control behavior! Human behavior is largely under top-down influences, but may be affected subtly by pheromones It is unclear whether molecules such as androstenone even qualify as pheromones - they may be just like other odour molecules Pheromones

“It is now possible to manufacture synthetic human pheromones and such compounds are often used in research as they are relatively easy to make, convenient to store, and easy to apply.” Pheromones

Upcoming: Read article by Gregory for February 16 th Read chapter by Pinker for February ~28 th

Vision

Seeing Seeing is the process of converting electromagnetic radiation into a conscious mental event

Seeing visual system faces many challenges –too much information –too little information –conflicting information –ambiguous information

Seeing too much information

Seeing too little information

Seeing Conflicting Information

Seeing Ambiguous information

Seeing We will consider two aspects of vision to explore how the brain overcomes these challenges: –Seeing depth –Seeing in color

Seeing Remember that the only information the brain gets is a 2D pattern of light on each retina

Seeing Remember that the only information the brain gets is a 2D pattern of light on each retina Our rich vivid visual experience is built out of those sparse inputs!

Seeing Remember that the only information the brain gets is a 2D pattern of light on each retina Our rich vivid visual experience is built out of those sparse inputs! Put another way, everything your brain needs to “see” is encoded in those patterns of light energy

Seeing Remember that the only information the brain gets is a 2D pattern of light on each retina Our rich vivid visual experience is built out of those sparse inputs! Put another way, everything your brain needs to “see” is encoded in those patterns of light energy …well almost everything

Light is an oscillation (a wave) in the electromagnetic field Light

What are some characteristics of light waves? Properties of light

What are some characteristics of light waves? – amplitude/intensity - how big of a fluctuation in the field/how many waves – frequency - how many fluctuations (waves) pass by a certain point in a given period of time – polarization - the orientation of the waves Properties of light

What perceptions are associated with those physical properties? Properties of light

What perceptions are associated with those physical properties? – Intensity is associated (loosely) with brightness – Frequency is associated (very loosely) with color – Polarization isn’t sensed by humans (but it is by some insects and birds!) Properties of light

Light The spectrum is the range of frequencies of electromagnetic waves

The eye – curved cornea – lens – retina – fovea – optic disk Using Light

Light is focused on the retina by the curvature of the cornea and the lens – Flat lens (relaxed muscles) focuses distant points Using Light

Light is focused on the retina by the curvature of the cornea and the lens – Accomodation: Bulged lens (muscles flexed) focuses on near points Using Light

Light is focused on the retina by the curvature of the cornea and the lens Constriction of the pupil limits how much light gets in AND reduces the amount of focusing required of the lens Using Light

photoreceptors transduce incoming light ganglion cells send signals along to the brain The Retina has layers of cells