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

• 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

Sensory Systems: Auditory

What do we hear?

• Sound is a compression wave:

When speaker is stationary, the air is uniformly dense

Speaker Air Molecules

What do we hear?

• Sound is a compression wave:

Speaker

When the speaker moves, it compresses the air in front of it.

What do we hear?

• Sound is a compression wave:

The speaker moves back leaving an area with less air behind - called rarefaction

CompressionRarefaction

What do we hear?

• Sound is a compression wave:

Speaker

The speaker moves forward again starting the next wave

Compression

Rarefaction

What do we hear?

• Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time

time ->

Air Pressure

Period - amount of time for one cycle

Frequency = number of cycles per second (1/Period)

Properties of a Sound Wave

• 1. Amplitude: difference in air pressure between compression and rarefaction (Sound Pressure Level)

Properties of a Sound Wave

• 1. Amplitude: difference in air pressure between compression and rarefaction (Sound Pressure Level)

– What is the perception that goes along with the sensation of sound amplitude?

Properties of a Sound Wave

• 1. Amplitude: difference in air pressure between compression and rarefaction (Sound Pressure Level)

– What is the perception that goes along with the sensation of sound amplitude?

LOUDNESS

Properties of a Sound Wave

• 2. Frequency: how many regions of compression (or rarefaction) pass by a given point per second (expressed in Hertz)

Properties of a Sound Wave

• 2. Frequency: how many regions of compression (or rarefaction) pass by a given point per second (expressed in Hertz)– What is the perception that goes along with the

sensation of frequency?

Properties of a Sound Wave

• 2. Frequency: how many regions of compression (or rarefaction) pass by a given point per second (expressed in Hertz)– What is the perception that goes along with the

sensation of frequency?

PITCH

Sensing Vibrations

Sensing Vibrations

• Outer ear transmits and modifies sound (critical for sound localization)

Sensing Vibrations

• Middle ear turns compression waves into mechanical motion

oval window

stapes

Sensing Vibrations

• Middle ear turns compression waves into mechanical motion

Ear Drum

Oval window

Sensing Vibrations

• Middle ear turns compression waves into mechanical motion

Ear Drum

Oval window

Compression Wave

Sensing Vibrations

• The cochlea, in the inner ear, is a curled up tube filled with fluid.

Auditory Nerve to Brain

Sensing Vibrations

• Inside the cochlea is the basilar membrane• Movement of the oval window causes ripples

on the basilar membrane

Sensing Vibrations

• Basilar membrane measures the amplitude and frequency of sound waves

– amplitude (loudness)

–frequency (pitch)

Sensing Vibrations

• Basilar membrane measures the amplitude and frequency of sound waves

– amplitude (loudness) - magnitude of displacement of the basilar membrane

–frequency (pitch)

Sensing Vibrations

• Basilar membrane measures the amplitude and frequency of sound waves

– amplitude (loudness) - magnitude of displacement of the basilar membrane

–frequency (pitch) - frequency and location of displacements of the basilar membrane

Sensing Vibrations

• Basilar membrane measures the amplitude and frequency of sound waves

–frequency (pitch) - frequency and location of displacements of the basilar membrane