Psychology- a Complete Introduction
Page 5
According to Broadbent, the meaning of the messages is not taken into account at all by the filter. All semantic processing (i.e. processing of the meaning of the information) is carried out after the filter. So whatever message is sent to the unattended ear is not understood – even though parts of it might be remembered. For example, we might recall that a female voice spoke in the unattended ear but not what she said.
Broadbent’s theory and the research it was based on have attracted criticisms:
• Listening to two channels at the same time is quite hard for people not accustomed to doing this, so this difficulty could account for Broadbent’s findings rather than the attentional system.
• It is possible that the unattended message is analysed thoroughly but that participants simply forgot it; this could be a memory issue rather than an attentional one.
• Analysis of the unattended message might occur below the level of conscious awareness (see the ‘Spotlight’ below).
• The Cocktail Party Phenomenon disproves Broadbent’s theory; this is when we can pick out our own name in a background buzz of noise even when we are not attending to the general noise.
Spotlight: Unconscious information processing
Von Wright et al. (1975) found that we might process information even when we are not aware of doing so. In this research, a word was presented to participants alongside a mild electric shock. When the same word was later presented to the unattended channel, participants registered an increase in galvanic skin response (indicative of emotional arousal and analysis of the word in the unattended channel).
A slightly different perspective is taken by Treisman (1964). She maintains in her Attenuation Model that the filter that Broadbent referred to doesn’t eliminate stimulation, but attenuates it (or turns down its volume) so that it is still available for further processing. Thus, if there are several sources of noise in a room (e.g. the TV, your kids talking, the baby crying), we can turn down the volume of all except the one we are attending to (e.g. the kids). This would explain why, if we heard our name, we would pick up on that.
Treisman, then, puts the filter at a slightly different place in the bottleneck. She suggested that messages are processed in a systematic way, beginning with analysis of physical characteristics, syllabic pattern and individual words. Only after this are grammatical structure and meaning processed. It will often happen that there is insufficient processing capacity to permit a full analysis of unattended stimuli, in which case later analyses will be omitted. This theory neatly predicts that it will usually be the physical characteristics of unattended inputs that are remembered rather than their meaning.
To get through the filter, items have to reach a certain threshold. All the attended/selected material will reach this threshold. Some items will retain a permanently reduced threshold, for example your own name or words/phrases like ‘help’ and ‘fire’ – this is why we will hear these against a background of noise.
Selective attention can be hampered by poor sleep, brain injury or disorders such as autism, learning disabilities or attention deficits. Selective attention can also be used to purposely draw attention to an object or person and ad agencies are always trying to think of clever ways to draw a person’s selective attention to their products.
Perception of pain
Compared to our understanding of vision and hearing, the perception of pain and exactly what factors influence it are not well understood. There are cases of people experiencing pain without any physiological reason. Different people also have different pain thresholds that make pain perception hard to understand and research. Three of the best-known pain theories are discussed here, although none of them explain all of the phenomena associated with pain perception.
‘The perception of pain involves far more than mere sensation. The affective and evaluative components of pain are often as important as the production and transmission of the pain signal.’
George R. Hansen and Jon Streltzer, ‘The psychology of pain’, Emergency Medical Clinics of North America 23 (2005): 339
Specificity Theory: this was one of the first modern theories to explain how we perceive pain. It holds that specific pain receptors transmit signals to a ‘pain centre’ in the brain and that it is this centre that produces the perception of pain. However, the theory does not account for the wide range of psychological factors that affect our perception of pain.
Pattern Theory: this holds that pain signals are sent to the brain only when stimuli group together to produce a specific combination or pattern. The theory does not suggest specialized receptors for pain. Rather, the brain is merely viewed as a message recipient. Despite its limitations, the Pattern Theory did set the stage for the Gate Control Theory that has proved the most influential and widely accepted pain theory so far.
Gate Control Theory: Ronald Melzack and Patrick Wall proposed the Gate Control Theory in 1965. The theory can account for both ‘top-down’ brain influences on pain perception (see ‘Factors that affect the perception of pain’ below) as well as the effects of other bottom-up stimuli in appearing to reduce pain. It proposed that there is a ‘gate’ or control system in the spinal cord through which all information regarding pain must pass before reaching the brain. According to British researchers from University College London, this explains why rubbing a scraped knee or banged elbow really does make the pain go away. It seems that the nerve signals from this tactile stimulation can interact, at the spinal cord level, with those signals transmitting painful sensations. When there is pain from a peripheral site of the body, such as the hand or foot, this painful signal travels along a peripheral nerve until it arrives at the spinal cord for transmission to the brain. However, at the spinal cord level there may be many different types of sensations coming in from around the body (such as touch, vibration and heat) that will ‘compete’ for transmission to the brain. It is thus believed that the brain’s perception of pain could be reduced by multiple sensory signals arriving at the spinal cord at the same time.
Spotlight: Pain as a ‘signal’
It has been shown in cancer patients that the affective component of pain can be completely blocked by frontal lobectomy (which involves cutting nerves to the frontal cortex). Lobectomized patients still register severe pain, but it doesn’t ‘bother’ them. Pain can thus be viewed as merely a ‘signal’ that something is wrong somewhere in the body, until it reaches the emotional brain, where this signal becomes what we feel as pain.
FACTORS THAT AFFECT THE PERCEPTION OF PAIN
• Context: the perception of even acute pain is highly dependent on the context in which it occurs. There are, for example, reports of soldiers in battle who suffer a compound fracture and report only twinges of pain.
• Attention: focusing one’s attention on pain makes the pain worse. Patients who are hypochondriacs are thought to be over-vigilant about bodily sensations. It has been found that by attending to these sensations, they amplify them to the point of that they feel painful. Conversely, distracting patients is highly effective in reducing their pain.
• Anxiety: anxiety, fear and a sense of loss of control contribute to pain. Treating anxiety and providing psychological support have been shown to improve pain and reduce analgesic use. Improving patients’ sense of control and allowing them to participate in their care is also helpful. For painful medical procedures, it is advised to prepare needles and other equipment out of sight from the patient. It is also helpful to distract patients with conversation about subjects that interest them, such as their hobbies or family.
• Learned pain: pain can be a learned response, rather than a purely physical problem. In some cases, pain can be entirely ‘in the mind’; I recall an experience as a small child when I fell and cut my knee. My older brother asked me whether it hurt, to which I responded that I was fine. Only when I saw blood gushing out of the knee did I start to feel the pain (as I had, presumably, learned to associate blood with pain).
Case study:
Phantom pain
Phantom pain sensations are described as perceptions that an individual experiences relating to a limb or an organ that is not physically part of the body (e.g. through amputation). It has been known that at least 80 per cent of amputees experience phantom sensations at some time in their lives. They may experience some level of this phantom pain and feeling in the missing limb for the rest of their lives. Little is known about the true mechanism causing phantom pains, and it used to be thought that the pains were ‘psychological’; experts now recognize that these are real sensations originating in the spinal cord and brain.
Early accounts for phantom pain claimed that the pain was the result of neuromas formed from injured nerve endings at the stump site that were able to fire abnormal action potentials. It is now thought that phantom pain can be at least partially explained as a response to mixed signals from the brain. After an amputation, areas of the spinal cord and brain obviously lose input from the missing limb but the brain adjusts to this loss in unpredictable ways. The result can trigger the body’s most basic message that something is not right – which we feel as pain.
Studies also show that, after an amputation, the brain may remap the part of the body’s sensory circuitry that relates to the missing limb to another part of the body (often the face, surprisingly). In other words, because the amputated area is no longer able to receive sensory information, the information is referred elsewhere – from a missing leg to a still-present lip, for example. So when the lip is touched, it’s as though the missing leg is also being touched. Because this is yet another version of tangled sensory wires, the result can be pain. This is referred to as cortical remapping and there is some evidence from functional MRI scans to support this.
Phantom pain can be treated with drugs, or, more recently, a technique called Mirror Box therapy. The patient places the good limb into one side of the box and the stump into the other. The patient then looks into the mirror on the side with the good limb and makes ‘mirror symmetric’ movements, as we do when we clap our hands. Because the subject is seeing the reflected image of the good limb moving, it appears as if the phantom limb is also moving. Through the use of this artificial visual feedback it becomes possible for the patient to ‘move’ the phantom limb, and to unclench it from potentially painful positions.
• Expectations: studies have shown that minor whiplash injuries can affect people differently, depending on the expectations of their culture and location. Similarly, if people believe that they should find something painful, they are more likely to do so.
Dig deeper
Listen to Donald Broadbent talk about the Cocktail Party Phenomenon:
http://www.bbc.co.uk/programmes/b01gvkw7
Learn more about selective attention by watching the Invisible Gorilla clip or reading the book it inspired:
http://www.theinvisiblegorilla.com/videos.html
For more on optical illusions:
http://www.bbc.co.uk/news/magazine-11553099
Fact-check
1 What is perception?
a Seeing things that are not there
b Hearing things that we cannot understand
c Making sense of our sensations
d When we hear our name in a crowded room against background noise
2 We see faces in patterns because:
a Faces jump out at us
b We are hallucinating
c We imagine the faces
d We have a natural tendency to perceive familiar objects in patterns
3 Which of the following is not a component of Gibson’s Theory of Direct Perception?
a Optic Flow Patterns
b Clarity
c Invariant Features
d Affordances
4 Which of the following is not a Gestalt Theory of Perception principle?
a Principle of longitude
b Principle of proximity
c Principle of similarity
d Principle of closure
5 Which of the following does not help us perceive depth and/or distance?
a Texture
b Size
c Shading
d Symmetry
6 The sensory buffer is:
a Where visual illusions happen
b The basis for understanding constancy
c Where our sensations are filtered
d The name for top-down processing
7 Selective attention is unlikely to be hampered by:
a Poor sleep
b Brain injury
c Learning disabilities
d Exercise
8 Which of the following is not a theory of pain?
a Pattern Theory
b Gate Control Theory
c Specificity Theory
d Context Theory
9 Which of the following is not a factor that can affect the perception of pain?
a Context
b Expectations
c Closing the eyes
d Anxiety
10 Phantom pain is:
a When amputees imagine that they can feel pain
b When amputees are distressed about their missing limb
c When amputees can feel pain from the missing limb
d Psychological
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Memory
Memory is at the heart of cognitive psychology and underlies everything: how we talk, walk, learn and feel. What we call memory is actually a three-stage process involving 1) encoding of information (laying down the memories), 2) storage of that information and then 3) retrieval of those memories.
‘Memory is the means by which we draw on our past experiences in order to use this information in the present.’
R. J. Sternberg, ‘The theory of successful intelligence’, Review of General Psychology 3 (1999): 292–316
Encoding
In Chapter 3 we talked about how sensory information reaches our brains via the process of perception. Encoding is the way that this information is processed, ready for storing. There are three main ways in which information can be encoded:
1 Visual (picture): for example, we store the memory by visualizing it as an image.
2 Acoustic (sound): here we store the information as a sound (this explains why we sometimes get words that sound the same mixed up when we try to remember them).
3 Semantic (meaning): here the object is stored in terms of what it means rather than as an image or sound.
It is thought that we use acoustic coding more in the short term but semantic memory for longer-term memory storage.
It should be noted that we are not always aware of encoding – this is not something that always takes place at a conscious level; encoding happens automatically. For example, if I were to ask what you ate for your evening meal last night, you will probably remember, even though you made no effort at the time to encode the information. However, such unconscious encoding is likely to result only in short-term memory; if we are to recall material in the longer term, we need to work at encoding it (as any student will know).
Storage
Memory storage affects how long memories last (duration) and how much is stored (capacity). The way information is stored affects the way it is later retrieved. There are a number of different theoretical approaches to how these storage systems work.
ATKINSON AND SHIFFRIN’S (1968) MULTISTORE MODEL
According to this approach, there are three primary types of memory storage system:
• Sensory memory: this is the storage system that occurs as the initial stage in the memory process. However, this sensory information is ‘stored’ only for a very short time (less than half a second for visual stimuli and three to four seconds for auditory) because it is ‘raw’ (i.e. unprocessed). This is to prevent us being overloaded – we are bombarded with so many sensory stimuli that we couldn’t possibly store them all. Only those bits of information that we attend to and process will pass from sensory memory to deeper storage systems. The ability to look at an item, and remembe
r what it looked like with just a split second of observation, is an example of sensory memory. It is out of our control and is an automatic response. There are thought to be two types of sensory memory: visual sensory memory (also known as iconic memory) and auditory sensory memory (echoic memory).
• Short-term memory (STM): our short-term memory, or working memory, is where our active processing happens and information can be held here for around 20–30 seconds. Our STM capacity is very limited (see the ‘Spotlight’ below). We can keep the information in STM longer if we rehearse it, but otherwise the data will then be lost – unless we pay further attention to it, in which case it will pass to the next stage of long-term memory.
Spotlight: Seven, plus or minus two
Short-term memory has a limited capacity: it can store about seven pieces of information, plus or minus two pieces. George A. Miller (1956), when working at Bell Laboratories, conducted experiments showing that the store of short-term memory was 7±2 items (the title of his famous paper was ‘The Magical Number 7±2’). A method called ‘chunking’ can help to increase the capacity of short-term memory by combining small bits of information into bigger chunks – but we can still recall only around seven such chunks.
• Long-term memory (LTM): The information in our LTM is largely outside of our awareness, but it can be pulled into our working memory when needed. Some of this information is fairly easy to recall, while other memories are much more difficult to access. Our ability to access and retrieve the information from our LTM is what allows us to recall facts, to solve problems, to interact with others and make decisions. Long-term memory has an almost infinite capacity, and information in long-term memory usually stays there for the duration of a person’s life. However, this doesn’t mean that people will always be able to remember what’s in their long-term memory – they may not be able to retrieve information that’s there (see the section on ‘Retrieval’ below).