People: The Sensory Perspective People in Design Sensory - Senses – Now we could spend a whole semester just looking at the senses, they are very rich and detailed, but we have a lot of exciting things to cover in this module, so we’ll curtail it by just looking at one sense in detail (Vision) and cover the others in less detail. People: Sensory - Sight People in Design Sensory - Sight – – – The eye is a ball filled with fluid with light sensitive cells coated on the back of the eyeball It has a small hole in the front to let in light, with a lens to help focus the light on the cells on the back of the eye. The cells on the back of the eye transmit information through the optic nerve to the brain. People in Design Sensory - Sight People in Design To help understand what an incredibly sophisticated job the eye does, in terms of getting input from the external environment and processing the light waves, it is useful to look at the evolution of the eye. People in Design At some point in history the creatures that evolved to become human developed cells on their body that were sensitive to light (photosensitive cells) These were very useful for telling the difference between day and night. [Source: Wikipedia – File: Diagram_of_eye_evolution.svg] People in Design These cells evolved into a concavity, to protect the cells from casual damage, e.g. scrapes and scratches. [Source: Wikipedia – File: Diagram_of_eye_evolution.svg] People in Design The concavity further contacts so that there is a very small opening, this improvement helps to discriminate the direction of the brightness. [Source: Wikipedia – File: Diagram_of_eye_evolution.svg] People in Design Eventually a slowly specialize a transparent humour, in the eye to allow for colour filtering, blocking of ultraviolet radiation, and the ability to operate in and out of water [Source: Wikipedia – File: Diagram_of_eye_evolution.svg] People in Design The eye evolved lenses to improve the amount of light that reached the retina, and to focus the light exactly on the back of the eye. [Source: Wikipedia – File: Diagram_of_eye_evolution.svg] People in Design Finally a cornea and iris developed, this increases refractive power, eases circulatory problems, and can help control the amount of light entering the eye. [Source: Wikipedia – File: Diagram_of_eye_evolution.svg] People in Design Sensory - Sight – – The eye is like a digital camera in the sense that it has a lens in the front to focus the incoming light on the photosensitive cells that coat the rear of the eye. The digital camera does some processing on the images in terms of removing shake and balancing out the brightness, the human brain does a similar job, but significantly more processing. Visual Acuity Visual acuity clearness of vision, which depends on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain. It is a measure of the spatial resolution of the visual processing system and is usually tested in a manner to optimise and standardise the conditions. To this end, black symbols on a white background are used (for maximum contrast) and a sufficient distance allowed to approximate infinity in the way the lens attempts to focus. Visual Acuity Visual Acuity In the term "20/20 vision", the numerator refers to the distance in feet between the subject and the chart. The denominator indicates the size of the letters, specifically it denotes the separation at which the lines that make up those letters would be separated by a visual angle of 1 arc minute, which for the lowest line that is read by an eye with no refractive error (or the errors corrected) is usually 20 feet (6.1 m). The 20/x number does not directly relate to the eyeglass prescription required to correct vision, because it does not specify the nature of the problem corrected by the lens, only the resulting performance. Visual Impairment Classification Classification Description Partially Sighted 20/30 to 20/60 Low Vision 20/70 to 20/160 Legally Blind 20/200 to 20/1000 Totally Blind No light perception Contrast Sensitivity Contrast sensitivity is a measure of the ability to discern between luminances of different levels in a static image. Contrast sensitivity varies between individuals, reaching a maximum at approximately 20 years of age. This text is easier to read, than this text. According to Dr Daphne Bavelier, University of Rochester, playing video games may improve a person’s contrast sensitivity Interesting illustration of the complex relationship between vision and the brain. The Bucha effect The effect is named after a Dr. Bucha who identified the phenomenon in the 1950s when he investigated a series of unexplained helicopter crashes. The Bucha effect The pilots who had survived reported sudden onset of dizziness and confusion, causing them to lose control of their aircraft. The Bucha effect Dr. Bucha found that helicopter rotor blades, when turning at certain speeds, could cause flashes of sunlight at frequencies coinciding with the electrical frequencies of the central nervous system (brainwaves), inducing disorientation. The Bucha effect The problem was solved by a few different solutions: – – Tinting the window screen of the helicopter Tinted visors on the pilot’s helmet People: Sensory - Hearing - Taste - Smell - Touch People in Design Sensory - Hearing – The main organ of hearing is the ear. People in Design Sensory - Hearing – – The outer part of the ear collects sounds, which is focused and amplified in the middle part of the ear. When the sound reaches the ear drum (or tympanic membrane) and passes into the inner ear, which is coated with hair cells (whose job is convert the sounds in nerve impulses that the brain can understand). People in Design Sensory - Hearing – – – The frequencies that humans are capable of being heard are called audio or sonic. The range is typically considered to be between 20 Hz and 20,000 Hz. Frequencies higher than audio are referred to as ultrasonic, while frequencies below audio are referred to as infrasonic. People in Design Sensory - Hearing – – An important notion when considering hearing is “Loudness”, which is a quality of sound that is primarily a psychological interpretation of the physical signal strength of a sound (amplitude). The loudness that humans are capable of being heard are typically 15 dB and 140 dB. Hearing Impairment Classification Classification Who? decibels of hearing loss, or dB HL Mild For Children between 20 and 40 dB HL Mild For Adults between 26 and 40 dB HL Moderate For All between 41 and 55 dB HL Moderately Severe For All between 56 and 70 dB HL Severe For All between 71 and 90 dB HL Profound For All 91 dB HL or greater People in Design Sensory - Taste – The main organ of taste is the tongue. People in Design Sensory - Taste – – – Tastes is sensed through taste cells (called taste buds). There are about 100,000 taste buds that are located on the back and front of the tongue. Others are located on the roof, sides and back of the mouth, and in the throat. People in Design Sensory - Taste – The tongue has different regions to detect different flavours. People in Design Sensory - Taste – The tongue has different regions to detect different flavours. People in Design Sensory - Taste – – – The idea that the tongue has different regions that specialize in different flavours is a common misconception. This mistake is as a result of confusion in the translation of a 1901 German psychology paper into English. It actuality all taste sensations come from all regions of the tongue Taste Impairment Classification Classification Description Hypergeusia Abnormally heightened sense of taste Dysgeusia Distorted sense of taste Hypogeusia Decrease in taste sensitivity Ageusia Complete lack of taste People in Design Sensory - Smell – The main organ of smell is the nose. People in Design Sensory - Smell – – – Smell is achieved by specialized neurons at the top of your nasal passage. These neurons have hair-like projections called cilia that capture molecules coming off the object emitting the smell When the cilia capture these molecules this causes neurons to fire, and signals are sent to the brain. People in Design Sensory - Smell – – Olfactory fatigue (or adaptation) refers to the fact that after prolonged exposure to a particular smell, a person will no longer be able to detect it. For example, when entering a restaurant initially the smell of food is very strong, but after time the awareness of the smell fades to the point where the smell is not perceptible or is much weaker. After leaving the restaurant, the sensitivity is restored with time. People in Design Sensory - Smell – – Humans can distinguish more than 10,000 different smells. Research suggests that humans can detect individuals that are blood-related kin (mothers and children but not husbands and wives) from olfaction. Smell Impairment Classification Classification Description Hyperosmia Increased sensitivity to smell Dysosmia Distorted sense of smell Hyposmia Diminished sense of smell Anosmia Loss of the sense of smell People in Design Sensory - Touch – The main organ of touch is the skin. People in Design Sensory - Touch – The sense of touch is a very complex and diverse sensory system composed of the receptors which detect not only touch, but also temperature, body position, and pain. People in Design Sensory - Touch – At its simplest, the system works when activity in a sensory neuron is triggered by a specific stimulus such as heat; and this signal is passed to an area in the brain uniquely attributed to that area on the body—this allows the processed stimulus to be felt at the correct location. People in Design Sensory - Touch – Phantom Limb Syndrome: Approximately 60 to 80% of individuals who have had a limb amputated experience phantom sensations in their amputated limb, and the majority of the sensations are painful. People in Design Sensory - Touch – A number of treatments have been used to combat the sensation, include drugs, electrical stimulation, and Ramachandran’s Mirror Box treatment.