percept & cogn w5 lecture: the skin senses, hearing & perception summary

Proprioception

• sensing position and posture of body, limbs in space

• Proprioceptors

• Uses parietal cortex

• 6th sense

Tactile sensation

• position and structure of objects making contact with body

• Texture

• Weight

• Shape

Skin

• largest sense organ

Mechanoreceptors

• Have different receptive field sizes. Determine spatial resolution

• meissner’s corpuscles - touch

• Ruffini endings - warmth

Measuring the 2-point threshold

• the drawing compass thingy Pressed against the finger tip, 2 points

• Mechanism used to test if ppl can differentiate between pressure on one or two points

• Basically, does it feel like it is stabbing you once or twice?

• diff body parts diffferent sensitivity. Diff spatial resolution - more on fingertips than back of hand

Spatial resolution is bigger in vision than in finger tips (finger tips smaller)

Somatosensory cortex

• in parietal lobe, right next to central fissue

Topographic representation - homunculus

• neighboring regions of the skin are next to each other

• Hand gets big space, lips too

Helen Keller (case study)

• deaf and blind

• Used exclusively touch to learn about the world

• First deaf & blind person to earn a college degree

• Author, political activist, feminist

• Being deaf was harder than blind for her

Active touch (haptic perception) - Gibson’s cookie cutter experiment

• Active touch - participates actively with interacting (95% correct)

• Passive touch - experimenter pushes cookie cutter against participants palm (49% correct)

Braille

• is suited to the relatively low spatial resolution of touch

• If you blur braille, clearer than roman letters

Hearinv vs vision

• seen as very important, equally so

The importance of hearing

• signal events about our environment

• Emotions are influenced by sound, music, noise

• Hearing is essential for certain forms of communication (lang, music)

Sound & ear

• sound waves are produced through movement becase of pressure in the air (or other medium)

• Wavelengths and amplitude

Dimensions of sound

• frequency (Pitch) (think cycles per second)

• Amplitude (loudness)

Frequency

• 1 cycle per second. 1 Hz

• Human hearing (30Hz o 20 000Hz)

• Piano C middle is 262Hz

• dogs can hear more than we can (higher freq)

• Mice (higher frequency, can’t hear lower freq though)

Males and females ”typical” frequency

Male - 85Hz - 180Hz

Female - 165Hz - 255 Hz

Discrimination of mother’s speech

• in utero - baby can begin to discriminate sound

• 1-3 days post birth could discriminate bilingual language sound

• Can discriminate mother’s voice in approx 3 days (DeCasper & Fifer, 1980)

Human auditory system

• Pinna —› ear canal —› eardrum —›

• Basilar membrane in cochlea. Hair cells transudce sound energy to neural signal.

• Diff freq sounds trigger basilar membranee

Perception of loudness

• Loudness = decibel scale (a logarithmic scale)

• On this scale, 0 decibels (dB) is the sound pressure level (SPL) which is the threshold fr hearinng

• 20 = leaves rustling

• 40 = quet suburb at night

• 60 = 2 ppl having a conversation

• 70+ = annoying sounds (busy traffic, vacuum cleaner)

• 100 = subway train

• 110 = dance clubs

• 120 = propeller plane take off

• 120-130 = ”loud” rock band

• 130 = machine gun

• 140 = jet plane at take off

Hearing damage

• sudden loud noises (guns, fire crackers, etc)

• Repeated exposure to loud noises

• 100 dB and up I think

Hanson & Fearn (1975)

• college students who attended a concert once a month had igher thresholds

• Higher dB to identify 500-8000 Hz

Todd (2000) enjoy loud music

• measured SPLs (sound pressure levels) of 100dB and more in dance clubs in Manchester And other venues

• Bad, toooooo loud

• We probs like it because of rhythm and dance