by Sandi Mann
Spotlight: Participants or subjects?
When I was a student (admittedly, many years ago), we referred to those who took part in research as ‘subjects’. In recent years, there has been a move away from talking about them as ‘subjects’ and instead to referring to them as ‘participants’. The word ‘subject’ was thought to be demeaning and failed to give the appropriate respect to individuals who had kindly agreed to participate in a research study. In fact, researchers owe a debt of gratitude towards them, and referring to them as mere ‘subjects’ seems to objectify and dehumanize them.
Dig deeper
Classic psychological experiments that could never be carried out today for ethical reasons:
http://mentalfloss.com/article/52787/10-famous-psychological-experiments-could-never-happen-today
BBC Radio programme about the Hawthorne Effect:
http://www.bbc.co.uk/programmes/b00lv0wx
BPS Code of Human Research Ethics:
http://www.bps.org.uk/sites/default/files/documents/code_of_human_research_ethics.pdf
Fact-check
1 What is a hypothesis?
a A random expectation about what will happen in an experiment
b An educated guess about a relationship between variables in an experiment
c A statement of fact about two variables
d A demand characteristic
2 What is an experiment?
a What we do to test hypothesized relationships between variables
b Where we see what will happen if we do something to someone
c A set of hypotheses
d A prediction about what will happen
3 What is a control group?
a The group whose behaviour is controlled by the researcher
b The group who don’t meet the criteria for taking part in the study
c The group who don’t get the intervention that the experimental group gets
d A group who don’t know the aim of the study
4 If A and B correlate, this means that:
a A causes B
b B causes A
c A and B cause something else
d A and B are related to each other
5 Observational methods are useful when:
a We don’t know what is going to happen
b We don’t have a hypothesis
c It is not ethical to manipulate a variable
d We are worried about the Hawthorne Effect
6 Reliable studies are those that:
a Can be replicated
b Measure what they are meant to measure
c Reject the null hypothesis
d Are one-tailed
7 Which of the following is not a threat to internal validity?
a History
b Maturation
c Testing
d Location
8 Double-blind studies are those where:
a No one knows what the hypothesis is
b The experimenter knows what the hypothesis is but the participants don’t
c The experimenter knows what treatment group the participants are in but they don’t
d Neither the experimenter nor the participants know what treatment group they are actually in
9 The Hawthorne Effect states that:
a People act differently when they are being watched
b People act differently when they are taking part in psychological studies
c People act differently when they are at work than when they are at leisure
d People act differently with psychologists than other types of researchers
10 Psychological research studies may not be ethical if they:
a Don’t have well-thought-out hypotheses
b Have too many variables
c Are two-tailed
d Do not fully inform the participant about what the study involves
3
Perception and attention
Perception refers to how we make sense of our world; sensation alone is not enough – we have to interpret the sensory input in order to understand it. This is the process of perception and various theorists differ in how they believe these processes work. Understanding the process of perception helps us understand phenomena such as visual illusions, how we perceive depth and distance and even phantom pain. Of course, in order to perceive, we have to attend to the stimulation first, so this chapter also discusses various theories of attention.
Perception refers to the organization, identification and interpretation of sensory information in order to make sense of and understand the environment. Perception involves attending to signals from the nervous system, which in turn result from physical or chemical stimulation of the sense organs. For example, vision involves light striking the retina of the eye, smell is mediated by odour molecules, and hearing involves pressure waves. However, perception is not merely seeing or hearing, but making sense of what these sensations tell us.
Perception, then, is not the passive receipt of these signals but is shaped by learning, memory, expectation, and attention. Perception involves these ‘top-down’ effects as well as the ‘bottom-up’ process of processing sensory input. The ‘bottom-up’ processing transforms low-level sensory information to higher-level psychological information (e.g. extracts shapes for object recognition). The ‘top-down’ processing refers to a person’s concept and expectations (knowledge), and selective mechanisms (attention) that influence that perception.
A good example of this difference is illustrated by a recent experience of mine; I asked my husband for a lemonade and when I received the beverage I recoiled at its taste – ‘Urgh!’ I exclaimed, ‘It’s flat and tastes awful!’ My husband pointed out that it was meant to be flat as he had given me a still drink (traditional lemonade), not a carbonated one. I sipped it again and then decided it was actually quite nice. My ‘top-down’ processing had conflicted with my ‘bottom-up’.
Visual perception theory
This idea of perception as being a way to make sense of and to interpret our sensations goes some way to explain many visual phenomena such as illusions. Psychologists are divided on the extent to which we engage in top-down vs bottom-up processing, with Richard Gregory (1970) arguing that perception is a constructive process that relies on top-down processing and James J. Gibson (1966, 1972) taking a bottom-up view of perception. For Gregory, our memories and other processes play a crucial role in how we see things.
Spotlight: Information loss
A lot of information reaches the eye, but much is lost by the time it reaches the brain. Richard Gregory estimates that about 90 per cent is lost.
This top-down approach explains visual illusions such as the Necker cube or other images whereby the object can be seen in different ways (even though there is no change in sensory input) as our brain flips between different interpretations of the data. It also explains why we have a tendency to ‘see’ faces in mundane objects (see the case study below).
The Necker cube: which is the front of the box? There are two ways to visualize this and our brains can allow us to flip between each.
Gibson in 1966 argued strongly against the idea that perception involves top-down processing and criticized Gregory’s discussion of visual illusions on the grounds that they are artificial examples and not images found in our normal visual environments. He argued that we don’t need to ‘make sense’ of the visual world but can perceive it directly as there is enough information in the environment to do this. For Gibson, sensation is perception: what you see is what you get.
Case study: Face pareidolia
In 2004 a decade-old toasted cheese sandwich said to bear an image of the Virgin Mary was sold on the eBay auction website for $28,000, according to a report on the BBC. The original owner of the sandwich, a Mrs Duyser, says she noticed the image burned into her sandwich as she was about to tuck into it in autumn 1994. ‘I went to take a bite out of it, and then I saw this lady looking back at me,’ she said, in the Chicago Tribune
newspaper. The item has apparently inspired others to place dozens of spin-off items on the online auction site, including attempts at replica burnt toast, T-shirts, ornamental plates and domain names.
Other places where Jesus has apparently popped up include a Walmart receipt, a frying pan in Salford, UK, and a pizza in Brisbane, Australia.
According to a study published in the journal Cortex (Jiangang Liua et al. 2014), it is ‘perfectly normal’ to ‘see’ such images because of a phenomenon called ‘face pareidolia, the illusory perception of non-existent faces’ caused by the interaction between the frontal cortex, the part of the brain that helps produce ‘expectations’ of what an object should look like, and the posterior visual cortex, the part that processes the image. That is, we are wired to interpret data that we see as something recognizable – primarily faces – and familiar faces will be ‘recognized’ the most.
Three important components of Gibson’s ‘Theory of Direct Perception’, as his views came to be referred to, are Optic Flow Patterns (changes in the flow of the visual array provide important information about the perception of movement), Invariant Features (such as texture that always occurs in the same way and thus gives us valuable data), and Affordances (environmental cues such as the knowledge that objects look smaller the further away they are). According to Gibson, these components, and others, are what help us make sense of our visual world.
The Gestalt Theory of Perception
If the key to Gregory’s top-down approach to understanding perception is inference, and the key to Gibson’s bottom-up approach is direct perception of unchanging elements, then the key to the Gestalt approach to perception is organization. Gestalt psychology was founded by Germans Max Wertheimer, Wolfgang Kohler and Kurt Koffka and focused on how people interpret the world. According to Gestalt psychology, the whole is different from the sum of its parts. Based upon this belief, Gestalt psychologists developed a set of principles to explain perceptual organization, or how smaller objects are grouped to form larger ones. These principles are often referred to as the ‘laws of perceptual organization’. For example, when we see a person, we do not see them as a collection of body parts – arms, legs, nose, ears and so forth. We organize them into a person and recognize them as such. In fact, we might barely notice the individual parts, even though we can see them (which is why changed features, such as new eyewear or a moustache, often fail to be noticed).
The Gestalt Theory of Perception is based on six main principles that govern how we organize sensations so that they make sense:
• The principle of proximity (or contiguity) states that things that are closer together will be seen as belonging together, as here:
XXXXXXX X X
Thus the Xs grouped together look like part of a cluster rather than separate; this prevents us having to analyse each stimulus separately.
• The principle of similarity states that things which share visual characteristics – such as shape, size, colour, texture, value or orientation – will be seen as belonging together.
• The principle of figure and ground states that we see objects as either figure (distinct elements of focus) or ground (background on which the figure rests). For example, the writing on this page is the ‘figure’ and the white background is the ‘ground’.
• The principle of good continuation states that we prefer continuous figures rather than separate ones (so we will see an X as a letter rather than four separate lines)
• The principle of closure is a tendency to close simple figures. This results in a effect of filling in missing information to make a whole, as shown, for example, in the World Wildlife Fund panda logo and the IBM logo.
• The principle of symmetry describes the instance where the whole of a figure is perceived rather than the individual parts that make up the figure. The mind perceives objects as being symmetrical and forming around a central point. It is perceptually pleasing to divide objects into an even number of symmetrical parts. Therefore, when two symmetrical elements are unconnected, the mind perceptually connects them to form a coherent shape. For example, consider:
[ ]{ } [ ]
We tend to see the above as three pairs of symmetrical brackets rather than as six individual brackets.
PERCEPTUAL CONSTANCY
How do we know that a building in the distance is tall and not as tiny as it appears in our field of vision? Perceptual constancy refers to our ability to understand that objects stay constant even if we perceive them differently. There are typically three constancies:
• Size constancy refers to our ability to see objects as maintaining the same size even when our distance from them makes things appear larger or smaller. This holds true for all of our senses. As we walk away from our radio, the song appears to get softer. We understand, and perceive it as just as loud as before, the difference being our distance from what we are sensing.
• Shape constancy allows us to perceive a plate as still being a circle even though the angle from which we might view it appears to distort the shape; we recognize a coin even if we see it from side on, and so on.
• Brightness constancy refers to our ability to recognize that colour remains the same regardless of how it looks under different levels of light. We know that the bright-green T-shirt we are wearing has not changed colour even though it looks darker indoors than outside.
PERCEPTION OF DEPTH AND DISTANCE
We perceive distance using both monocular and binocular cues.
Monocular cues are those cues that can be seen using only one eye and include:
• Size: larger images are perceived as closer to us.
• Texture: objects with more detailed textures are perceived as being closer because the texture of objects tends to become smoother as the object gets farther away.
• Overlap: those objects covering part of another object are perceived as closer.
• Shading: closer objects cast longer shadows that will overlap objects which are farther away.
• Clarity: objects tend to get blurry as they get farther away; therefore clearer or more crisp images tend to be perceived as closer.
Binocular cues refer to those cues in which both eyes are needed to perceive. There are two important binocular cues:
• Convergence: the closer an object, the more inward our eyes need to turn in order to focus. Thus, we know that the more our eyes converge, the closer the object must be.
• Retinal disparity: each eye sees a slightly different image and these are then sent to our brains for interpretation; the distance between these two images, or their retinal disparity, thus provides another cue regarding the distance of the object. Retinal disparity thus marks the difference between two images and increases as the eyes get closer to an object.
Visual attention
‘Everyone knows what attention is. It is the taking possession by the mind in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought… It implies withdrawal from some things in order to deal effectively with others.’
William James, Principles of Psychology (New York: Henry Holt & Co., 1890)
Visual perception is more than seeing. It is more than making sense of what we see. It is also about what we see – and why we see or pay attention to some aspects of our visual field and not to others. We can’t attend to everything – there is far too much material bombarding our senses (not just our vision) and we would suffer from sensory overload. Our brains cope by selectively attending to what we consider important.
Advertisers and those in marketing know this. They know that we don’t see everything in a visual field equally and work hard at making certain areas salient to us, or by working with those features that are most likely to grab our attention. Our attention is determined by both ‘bottom-up’ and ‘top-down’ factors:
• Bottom-up factors are those elements of the visual field that attract attention due to their properties (e.g. colour, contrast and orientation).
• Top-down factors are elements outside those within the visual field that influence how we perceive things and include goals, memories and interests.
Selective attention and hearing
Related to the idea of visual attention is the wider concept of selective attention. This refers to the processes by which we attend or notice one part of a stimulus but not another. This is usually studied in relation to auditory perception rather than visual, and psychologists are interested in why we attend to what we do and why we might be less attentive to other things going on around us.
Many theories of selective attention take a bottleneck approach, whereby it is assumed that there is some kind of filter or bottleneck that prevents all information getting through. Perhaps the best-known of these theories is Broadbent’s Filter Model. Broadbent (1958) argued that information from all the stimuli presented at any given time enters what is termed a sensory buffer. Inputs are then selected on the basis of major physical characteristics for further processing by being allowed to pass through a filter. Because we have only a limited capacity to process information, this filter is designed to prevent the information-processing system from becoming overloaded. The inputs not initially selected by the filter remain briefly in the sensory buffer and, if they are not processed, they decay rapidly.
Broadbent used dichotic listening techniques to reach his conclusions. This is an experimental method aimed at investigating selective auditory attention. Messages are sent to each ear simultaneously and the participant is asked to repeat back what they have heard. Using this method, Broadbent discovered that we prefer to repeat ear by ear – that is, we can only process one ‘channel’ of information at a time, leading to what he called the ‘single-channel model’.