How Attention Works

Editor's Notes

1. Capturing a customers’ attention and creating associations in their memories are key concerns for any business or non-profit. The intention of this paper is to give readers some of the hard facts surrounding how attention and memory work, and, by implication, how advertising works. The paper consists of a broad review of some of what science knows about attention and memory. In addition, the author has interspersed the sections with implications for business. The hope is that these implications will prompt the reader to consider the facts presented to them in light of their own business (or any other) context. Obviously, this paper deals with massive subjects that can easily fill many volumes beyond what can be contained in a paper of 30 pages, and so, some over-simplifications may occur. Regardless, whether coming from a business or social background, this paper should give you a better idea of how people process your messages.
2. Contents:How do we process our environment?What is the path that stimuli go through?What are the factors that capture our attention?What about stimuli that we don’t consciously process?
3. Most people have an idea of what is meant by the term attention. However, as with most concepts, once we start picking it apart, it reveals itself to be far more complex than originally thought. Before we go down the route of reducing attention to its component parts, let us first try to understand it holistically. Marvin Chun and colleagues [2010] point out that: “We should… abandon the view of attention as a unitary construct or mechanism, and consider attention as a characteristic and property of multiple perceptual and cognitive control mechanisms.” “Attention” refers to information processes that occur across many areas of the brain. It does not only refer to the stimuli that we choose to focus our eyes on. It also refers to the mechanisms that govern, amongst other things, which sounds we tune in to, which odours we discern, which memories we recall and which option we choose when faced with a decision. In an environment that bombards us with millions of pieces of stimuli from moment to moment, attention systems are the filters that help us prioritise specific stimuli, streamline their processing and make good decisions. Attentional mechanisms are vitally important to organisms that have a limited processing capacity such as all animals, including humans. Note that it is important to make the distinction between “attention” and “awareness” as they are not the same thing. Attending to an object does not ensure awareness of the object. Our brains can unconsciously attend to many more things than we become consciously aware of as we will see.
4. The topics touched on in this presentation have far-reaching implications for all level of society, both in our personal or business lives.
5. Selection refers to our ability to select between the multiple stimuli competing for our attention at any one time. It has nothing to say about how well a stimulus will be processed; merely which stimuli are elevated above competing stimuli and which are suppressed. Generally speaking, our brain’s goal is to choose the stimulus most immediately relevant or valuable for our survival. When we do not have a particular goal directing our attention, we are more apt to focus on any stimulus that is novel or surprising, and that maximises our chances of survival. While most of us do not run the risk of inadvertently happening on a hungry lion in our modern lives, we are still hardwired to focus on stimuli that promote survival [Posner, 2008]. As social apes, navigating social groups is also a matter of survival and, thus, we are particularly sensitive towards social cues such as facial expressions, eye movements and other forms of body language. Attention does not only apply to the external world around us though. We also need to apply attention to our own thoughts and decision-making processes. Selection is a vital part of any recollection or decision-making process – we need to attend to appropriate memories to recall them and we need to focus on the elements of a task in order to make the right decision. A popular example of selection failure is Simons & Chabris’ [1999] gorilla experiment. This ‘inattentional blindness’ effect perfectly illustrates the power of the selection process in attention. In the above slide, I have used a remake of the Simons and Chabris experiment that uses a moonwalking bear...
6. Why don’t we see the bear?
7. Internal and external attentionAs mentioned, attention is a far broader concept than most people realise. It can be split between two main focuses of attention: internal and external. External attentionrelates to the objects and stimuli in the world around us such as people, furniture, buildings and advertisements. Such stimuli are processed through our ‘modalities’, including sight, hearing, smell, taste and touch. For example, as you read this sentence, your attention is currently focused externally on the paper in your hand or on your screen. Internal attention refers to the intangible thoughts, associations and memories that we all hold within our heads. Think of an incident in your past involving a family member or friend. Perhaps it was your 10th birthday party when you received a new bicycle, or perhaps it was a time when you hurt yourself and your mother comforted you. The process by which you recalled this memory required attention, that is, the ability to sift through and focus on a specific memory while simultaneously supressing irrelevant memories. It also applies to our ability to select between multiple options or choices in mind and recall relevant information to make a correct decision such as when cooking the perfect meal. There is a heavy interaction between internal and external attention. For example, an external advert for Volkswagen Beetle might trigger a memory from your childhood, or, an internal goal to eat healthily might focus your attention on the salad rather than the cake.
8. Top-down versus bottom-up processingAnother way of thinking about external and internal attention is in terms of exogenous (external) and endogenous (internal) attention. Exogenous attentionworks in a bottom-up fashion whereby cues in the environment guide attention, making it stimulus-driven attention. Endogenous attention, on the other hand, is top-down, goal-driven attention arising from internal thoughts, memories and tasks. The manner in which our attention is directed (bottom-up or top-down) has implications for the types of stimuli we attend to and remember. Bottom-up processing implies that our attention (and thus our thoughts and memories) are guided by the cues in our environment without much conscious, directed thought on the observer’s behalf. Imagine yourself wandering aimlessly down a bustling street without any particular goal in mind. In this kind of situation you can be said to be ambiently processing the environment. In this mode, we process up to 40 distinct objects/stimuli at any one time [Posner, 2008] or about 10 items per second [Chun, Golomb & Turk-Browne, 2010]. It is in such a state that one might be strolling through Times Square and notice a Coca-Cola billboard. This is not to say that one will actively remember the billboard or be able to recall its contents, but, in such a state, the billboard is likely to activate our other associations with Coca-Cola and perhaps even add to or change them as we will discuss in more detail.  Top-down, endogenous processing is very different to bottom-up, exogenous processing. In this situation, our attention is guided by the goals and thoughts inside our head. Here, we have a target or goal in mind and we attend to those items that match our goal. This leads to a far narrower attentional focus. Imagine I task you up-front with counting the number of people wearing red T-shirts in Times Square. Your accuracy rate will be far higher than if I had only asked you to recall the number after having walked through Times Square. However, in order to more accurately count the number of red T-shirts, you would have had to sacrifice the processing detail of all other stimuli (including adverts). This is the trade-off we face as we shift resources from broad, ambient, bottom-up, exogenous processing to narrower, goal-directed, top-down, endogenous processing.The reason why most people miss the bear is because they are counting the number of times the ball is passed (a top-down goal). Their accurate count of passes comes at the expense of other details such as a person in a gorilla suit crossing the screen. If the viewer had been left to their own devices while watching the scene, they would very likely have noticed a gorilla crossing the screen.
9. So what is the actual process that stimuli go through?
10. The attention processHow can a billboard, or indeed, any other stimulus, activate and add to a person’s associations and memories if they do not remember seeing the ad or stimulus? It can because of the path that a stimulus takes when being processed.As mentioned, we can process about 40 items at a time. However, this only relates to “semantic processing”. At this level, our brains only process the stimulus up to the point of recognising and categorising it as either worthy of raising to awareness or not. In doing so, semantic processing can leave mental traces that can make an item more “top of mind” by priming the subject when exposed to related concepts [e.g. Greenwald, Draine, & Abrams, 1996; Shapiro, MacInnis & Heckler, 1997].A massive filtering effect exists though as we go from unconscious semantic processing to conscious awareness of the stimulus as it passes into short-term memory. Contrary to popular belief, we only become aware of a far smaller sub-section of the stimuli we actually process, and these are only the stimuli that our brains deem most relevant.The bottleneck between semantic processing and short-term memory exists due to the limited (but still impressive) processing capacities of the human brain. From processing about 40 items unconsciously, only about four chunks [Cowan, 2001] will be raised to our awareness in short-term memory at any one time, although the actual number varies depending on several factors [Miller, 1956; Cowan, 2001; Alvarez & Cavanagh, 2004; Awh, Barton, & Vogel, 2007], including processing modality and complexity of the objects in question.
11. Short-term memory capacity limits by modality/category:Visuals = 1-5 [Sperling, 1960; Alvarez & Cavanagh, 2004; Yee Eng, Chen & Jiang, 2005]Digits = 5-9 [Miller, 1956]Letters = ± 6 [Hulme, et al, 1995]Words = ± 5 [Hulme, et al, 1995]Short-term memoryAfter a stimulus passes through sensory memory, which would appear analogous to the pre-conscious processing stage (including semantic processing), a reduced set of the most salient inputs enter short-term memory. It is at this point that we become consciously aware of a stimulus. As Kihlstrom [1987] puts it, “[Short-term memory is] the locus of conscious awareness”.  Short-term memory allows us to remember simple lists and groups of items for a short period of time, ranging from a few seconds up to a minute, although the duration can be extended through the process of “rehearsal” (i.e. mentally repeating the stored contents to oneself). It is maintained by temporary patterns of neural activation which rehearsal reactivates and keeps alive. It is important to note that short-term and working memory are not the same thing. Short-term memory refers to the passive maintenance or storage of information without the manipulation of the information being stored. Working memory refers to a theoretical mental work space in which manipulations of multiple inputs from various sources, including short-term memory, long-term memory and external stimuli, are performed in order to produce an outcome (e.g. playing a game of Sudoku). Short-term memory’s capacity was famously deduced by Miller in 1956. Miller showed that most people can hold between five to nine (7 ±2) digits in short-term memory at any one time. However, while Miller’s estimate seems to hold for the recollection of digits, newer estimates by Cowan [2001] imply a more general capacity limit of about four chunks. However, even this is a rough estimate that varies dramatically depending on the complexity of the features of the stimuli being processed and the modality of perception.
12. Defining “chunks”:A chunk is a theoretical collection of several pieces of information relating to the same stimulus or concept. Features might include attributes such as the colour red, or a spherical shape; or, in the case of the complex notion of “justice”, fairness, retribution, morality, law, etc. “Chunking” is a useful strategy that allows our brains to treat a collection of information as if it were a single piece of information, thus freeing up our brains to handle more information at any one time. Cowan [1998] has shown that we are able to store about four chunks at any one time, although this varies depending on the input modality and several other factors. A chunk can contain about three to fours pieces of individual information [Broadbent, 1975].Example: After a single exposure, a cross-country runner could successfully recall 79 digits. He did this by chunking the digits into different running times e.g. 1518 was chunked as a three mile running time [Ericsson, Chase & Faloon, 1980].In business: Chunking is used in advertising, for example, when a brand splits up its phone number into rhyming chunks of about three digits each.
13. Okay, so what captures people’s attention?
14. Spatial attention is probably the most relevant type of attention for marketers as it refers to our ability to focus our attention on a specific region of space within our environment. For example, spatial attention allows us to shift our focus from the foreground to a sign in the distance, or to train our ear onto a sound behind us rather than on our left-hand side. A central problem for our brain is how to prioritise the various spatial objects in our environment. This is primarily a visual problem but applies to other modalities as well. Our brains spend a large amount of time working out where to look so as to ensure that we are always capturing the most important information possible. Therefore, it is of interest to understand what captures our attention. A good way to capture attention is to give the observer a cue (such as flash) which they can use to direct their attention to a target in the same position (such as a sign). The next natural question that arises is what types of cues and stimuli best capture our attention? Examples include:Emotionally charged stimuli [Phelps et al., 2006] and semantic (i.e. meaningful) relations such as the threat of violence or loss of belongings [Boynton, 2008]Social cues such as faces [Hershler & Hochstein, 2005] and gaze direction [Driver et al, 1999]Movement, including the onset of movement [Abrams & Christ, 2003], appearance of new objects [Phelps et al., 2006], movement amongst still objects [Franconeri & Simons, 2003], looming stimuli [Franconeri & Simons, 2003] and objects that are likely to collide with the observer [Lin et al., 2008]A distracting stimulus that shares some feature with the current target [Folk et al., 2002] Stimuli that differ from surrounding objects [Duncan & Humphreys, 1989; Itti & Koch, 2000] e.g. high contrast versus background (e.g. brightness, shape, colour) [Boynton, 2008]Stimuli that are cued in some way e.g. in predictable locations, by background context or past experience [Bar et al., 2004, Chun, 2000; Torralba et al., 2006]Expected rewards affect attention by increasing the focus on reward-related items and locations, and inhibiting non-reward items and locations [Libera & Chelazzi, 2006; Serences, 2008]Stimuli that contain specific features that are coded early in our brains’ visual systems such as orientation, direction of motion and colour [Boynton, 2008]
15. Defining “novelty”:Within the context of the brain, “novelty’ refers to stimuli that surprise our brain by contradicting its predictions of the external world (known as a “prediction error”). The greater the prediction error (i.e. the contradiction between what we expect to see and what we actually see), the greater the surprise, or “novelty”. This mechanism is modulated by neurotransmitters such as dopamine, acetylcholine and norepinephrine [Posner, 2008] which act as a kind of chemical brain currency whose pay-offs are large in the case of surprise and minimal in the absence of surprise [Montague & Berns, 2002]. The field of neuroeconomics concerns itself with understanding how a physiological ‘currency’ such as dopamine is used to direct our thoughts, actions and rewards. These processes occur on very short time scales, in the order of milliseconds. The figure in the slide gives us an experimental illustration of how this process works. These experiments unveil the mechanics behind how our brains orient themselves towards new and novel stimuli, and they also show the power of our expectations at a physiological level. If a prediction error occurs between what we expect to see and what we actually see, we receive a spike of a neuro-modulator such as dopamine. This encourages our brains to orient towards the stimulus associated with the spike. However, pre-existing expectations, cues and priming all play a role in mediating the magnitude of dopamine (and other neuro-modulator) spikes that occur due to a surprise (prediction error).Image description:A and B both show the same three rounds of brain recordings from a group of primates. A is the actual recordings, while B is a qualitative re-drawing of the results. In the experiment, the primates were rewarded with food. Sometimes they were cued to expect the reward (for example, by showing it to them in advance), while sometimes they were given the food when they did not expect to receive it. Observation row 1: We see that if the primate does not expect to receive a reward (R) because it has not been cued to expect one (“No CS”), it receives a dopamine spike right after receiving the reward (visualised by the increase in activity along the top line of A, or the grey bump in B). Observation row 2: If the primate expects to receive the reward (i.e. it has been cued, CS), then the dopamine spike occurs at the time of the cue and not at the time of reward. Observation row 3: If the primate is cued to receive a reward (CS), a dopamine spike occurs right afterwards. However, if the reward does not occur (No R), a subsequent negative dopamine spike occurs, cancelling out the initial positive cue spike.
16. Temporal attention,as the term implies, has to do with time. Temporal attention allows us to focus on stimuli that appear at different points in time in the same location. While similar to spatial attention in many aspects, temporal attention relies on an independent set of mechanisms to spatial attention [Chun, Golomb & Turk-Browne, 2010].We are able to detect a clearly defined category of objects (e.g. red shoes in a series of green shirts) when flashed before us at a rate of about 8-10 images per second [Potter, 1975] even though our ability to retain and report back on these scenes is more severely limited by our short-term memory capacities. Temporal attention exhibits an interesting phenomenon known as the “attentional blink”. The term refers to the fact that if we are told to look out for two targets (e.g. a pair of red shoes and a pair of blue trousers) amongst a series of objects (e.g. green shirts), our ability to do so will be dramatically reduced if the second target (blue trousers) appears within 0.5 seconds of the first target (red shoes) (see Figure 6 for a visual breakdown). Even though we do not become aware of the second target, it is processed up to a semantic level [Luck et al. 1996, Marois et al. 2004, Shapiro et al. 1997].
17. Most people can’t see the red shoes and the blue trousers in a single viewing if they are tasked with looking out for both.We can generally only see one or the other as the blue trousers appear within 0.5 secs after the red shoes. This falls with the “attentional blink” time period. During this period, our brain scrambles to change gear to identify the second target. This shifting of mental gears takes roughly 0.5 seconds, during which time we are essentially blind to other stimuli.
18. “Attentional blink” (perception). Inability to observe second target if < 0.5 seconds after first.“Psychological refractory period” (response/choice selection). There is a delay of 0.5 seconds before we are able to execute the second response when confronted with choice between two responses.“Task switching”.The cost of switching increases as the gap between the new task and the instruction to switch gets shorter. There always remains a residual switching cost, perhaps pointing to the fact that a new task must actually be executed in order to fully implement a switch.
19. Real world example…
20. This ad showed numerous scenes of people enjoying a product. The cuts become faster and faster, building to a crescendo.The increasingly fast cuts meant that respondents experienced an increase in NEGATIVE EMOTION towards the end of the advert. This is likely due to our brains’ inability to process the inputs fast enough, in line with processing bottlenecks like the attentional blink.
21. What about stimuli that we don’t consciously process?
22. Unconscious processing: subliminal and unattended stimuliProbably the most interesting area for marketers is whether we process all the stimuli in our environment (such as a billboard in the corner of our eye or a logo on a passer-by’s shoe), and what effect they have. Research shows that unconscious stimuli do affect cognition and action [Merickle & Daneman, 1998; Kiefer & Spitzer, 2000]. This section refers to two types of unconscious stimuli: stimuli that we are exposed to but do not perceive (i.e. subliminal stimuli) and stimuli that we perceive but our brains do not attend to (i.e. unattended stimuli).
23. Defining “subliminal”:The term is derived from the word “limen” which refers to the absolute minimum threshold above which we can detect the weakest possible stimulus for each modality (e.g. sight, sound). Hence, “sub-liminal” refers to stimuli that fall below the minimum threshold for detection by a modality [Kihlstrom, 1987].  Subliminal stimuli. Popular focus has fallen on the effects of “subliminal messaging”, a term which has caused moral panic over fears of mind control, with accusations being levelled against companies such as Coca-Cola for supposedly manipulating film viewers into buying Coca-Cola (even though the studies in question were conducted by independent researchers that were subsequently discredited) and musicians supposedly backmasking messages in their music that can only be heard when playing songs backwards. In both these examples, the effect of subliminal messages was shown to be negligible.Subliminal stimuli are processed up to a semantic level without being consciously perceived, raised to our awareness [Draine & Greenwald, 1998] or leaving a memory trace [Greenwald, Draine & Abrams, 1996]. This semantic activation primes us to respond more quickly and accurately to related concepts and stimuli. However, to observe a subliminal priming effect, the target behaviour must occur within 100-200 milliseconds after the subliminal prime [Kiefer & Spitzer, 2000]. So, while flashing a Coca-Cola logo during a film might prime audiences, it only lasts for 100-200 milliseconds.
24. Unattended stimuli. Research shows that our brains process stimuli in our environment up to a semantic level (e.g. “this is a chair”, “that item is dangerous”, etc.). Some are then raised to our conscious awareness by entering our short-term memory. While we may process about 40 items at a time in this way [Posner, 2008], this processing is all done without our awareness and the number of items that we actually become aware of is dramatically reduced. Confirmation bias, our tendency to select, process and remember information that is congruent with what we already believe, plays a role in determining whether a stimulus passes through semantic processing into conscious awareness, a necessary step for us to be consciously aware of something. For example, “I believe that the world is going to end in 2012, therefore I consciously attend to the news stories which confirm my belief and ignore the ones that disconfirm it”; or, “as an Apple fan, I am more likely to attend to the positive news about the brand, while ignoring or forgetting the bad news”.
25. Shapiro, MacInnis & Heckler [1997] showed that branded adverts that received minimal attention still improved the chances of the brand being considered for purchase by a subject during the same session, even if the subjects did not explicitly remember the ads.It has been found that the effects of stimuli perceived unconsciously by anaesthetized patients during surgery can last up to 24 hours [Merickle & Daneman, 1998]; perhaps implying that unconsciously perceived priming effects can last many hoursMerickle & Daneman also point to research by Poetzl who exposed patients to pictures of complex natural scenes for 100ms (long enough to perceive, but not long enough to consciously process all its details) and then asked patients to describe the pictures. The following day, Poetzl asked patients to describe the previous night’s dreams. He found that elements from the pictures found their way into patients’ dreams even though they had not reported them in their descriptions the previous day.
26. Lavie’s [2005] load theory helps us predict the level of processing an unattended stimulus will receive. Basically, the amount of processing that an unattended stimulus receives is directly related to the burden placed on our perceptions by the attended stimulus (known as “task difficulty”). If task difficulty is low, then excess attention resources will shift towards processing distractor stimuli. If task difficulty is high, distractor stimuli are less likely to be processed [Lavie 1995; Chun, Golomb & Turk-Browne, 2010]. Simply put, you are more likely to process a gorilla crossing your field of view while watching your neighbour gardening than while watching a football game in person. Distractor stimuli are more likely to be processed when there are fewer of them, although, doing so slows down the processing of the target that is being attended to. Increasing the load on an individual’s perceptions by adding more distractors until the load exceeds their attention capacity (i.e. overloading their attention capacity) results in the distractors actually being less-well processed as the individual devotes more resources towards maintaining focus on the task at hand. Consequently distractors end up providing less interference with the target stimuli [Lavie, 1995].
27. The Nike logo is more likely to be processed as a distractor stimulus when the task difficulty of the target is low (i.e. more likely in a quiet suburban street than in a bustling stadium).We are also more likely to notice the moonwalking bear in this kind of situation.
28. The coloured dots represent eye-tracking data i.e. where participantsare looking on the above image.Subjects were told to focus on the lion image, which is full of details. As a result, their gaze spent little time on the empty landscape.
29. This time the participants were told to focus on the landscape. However, this seen has relatively few details. As a result, more participants’ gazes were momentarily captured by the detailed lion scene.This is not necessarily a conscious capture as most participants’ were adamant that they maintain their attention on the landscape scene. Rather, this illustrates how our gaze works. Our eyes are constantly darting around our environment, even if our brain creates a solid image that does not show this darting.
30. Lavie actually refers to two kinds of task difficulty:“Perceptual load”, which relates to our limited capacity to process external stimuli “Central limitations”, which relates to our limited internal capacity for maintaining and manipulating items in working memory and similar functions such as task switching Interestingly, the effects of perceptual load and central limitations are opposite. Increased perceptual load (e.g. while in a stadium) decreases the processing of individual distractor details, while increased central load (e.g. working on a particularly challenging maths problem) actually increases the processing of distractor details as our executive functions lose control over the ability to focus our attention on the task at hand [e.g. de Fockert et al. 2001].
31. If subjects are able to recall the stimulus, they are more likely to experience a contrast effect (judgements opposite to the primed stimulus) when subsequently being exposed to similar stimuli. “For example, participants will rate a given weight as heavier if they had recently lifted a series of relatively lightweight objects than if they had not”. A person might consider an only-slightly-chilled Hunter’s Dry Cider as relatively less refreshing after seeing an ad containing an ocean of frozen Hunter’s Dry bottlesIf they cannot recall the prime, an assimilation effect (judgments consistent with the primed category) is more likely to occur. For example, after lifting a heavy weight, lighter weights might be perceived as heavier than they otherwise would. A person might consider Hunter’s Dry as more refreshing than it really is.
32. Conclusions
33. Perceptual filters, created by our own biases, beliefs, past experiences and our current intentions and goals, serve to filter out various stimuli from our environment. They play a massive role in what we consciously perceive and remember.Unconscious processing does happen, but it is context sensitive (e.g. I might buy a Coke after seeing an ad for it, but only if I am standing at the store shelf and intend to buy a carbonated soft drink anyway), and……what we actually process unconsciously depends on the task difficult, or load, of the target stimulus.
34. Hope you enjoyed this trip into the human mind 