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Chapter 04

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McGill University
Biology (Sci)
BIOL 303
Jonathan Fugelsan

Chapter 04: Paying Attention  Selective Attention - Selective Attention: The focusing of cognitive resources on one or a small number of tasks to the exclusion of others - Dichotic Listening Task:  A person listens to an audiotape over a set of headphones. On the tape are different messages, recorded so as to be heard simultaneously in opposite ears. Participants in a dichotic listening task typically are played two or more different messages and asked to “shadow” – that is, to repeat aloud- one of them.  Information presented at a rapid rate (~150 words/minute) so the shadowing task is demanding.  At the end of the task, participants are asked what information they remember from either message – the attended message or the unattended message.  Sometimes the tapes are recorded so that both messages are heard in both ears- called binatural presentation –and some researchers have used it in addition to dichotic listening tasks  The person must concentrate on the message to be shadowed. Because the rate of presentation of information is so fast, the shadowing task is difficult and requires a great deal of mental resources.  Fewer resources are available to process information from the nonshadowed, unattended message. - Cherry (1953) demonstrated in a classic study that people can, with few errors, shadow a message spoken at a normal to rapid rate.  When researchers later questioned these participants about the material in the unattended message, they could nearly always report accurately whether the message contained speech or noise, and if speech, whether the voice was that of a man or a woman.  When the unattended message consisted of speech played backwards, some participants reported noticing that some aspect of the message, which they assumed to be normal speech, was vaguely odd. - Participants could not recall the content of the unattended message or the language in which it was spoken.  In one variation of the procedure, the participants did not notice the language switch from English to German of the unattended message.  Participants in another experiment (Moray, 1959) heard prose in the unattended message and a short list of simple words in the unattended message. They failed to recognize the occurrence of most words in the unattended message. Filter Theory - Broadbent (1958) proposed a filter theory of attention, which states that there are limits on how much information a person, can attend to at any given time. The person uses an attentional filter to let some information through and block the rest. - The filter is based on some physical (in this particular example, basic acoustic) aspect of the attended message: the location of its source or its typical pitch or loudness, for instance.  Only material that gets past the filter can be analyzed later for meaning.  The filter selects information for later processing. - The meaning from an unattended message is not processed.  Broadbent’s filter theory maintains that the attentional filter is set to make a selection of what message to process early, typically before the meaning of the message is identified.  According to Broadbent’s model, it should not be possible to recall any of the meaning of an unattended message. - Broadbent believed instead that what is limited is the amount of information we can process at any given time.  Two messages that contain little information, or that present information slowly can be processed simultaneously.  For example: A participant may be able to attend simultaneously to more than one message if one repeats the same word over and over again, because it would contain little information. In contrast, messages that present a great deal of information quickly overcome the filter; fewer of them can be attended to at once.  The filter thus protects us from “information overload” by shutting out messages when we hear too much information to process all at once. - Moray (1959) – “Cocktail Party Effect”  Shadowing performance is disrupted when one’s own name is embedded in either the attended or the unattended message. Moreover, the person hears and remembers hearing his name. - Filter theory predicts that all unattended messages will be filtered out- - that is, not processed for recognition or meaning – which is why participants in dichotic listening tasks can recall little information about such messages. - Cocktail Party effect shows that people sometimes do hear their own name in an unattended message or conversation, and hearing their name will cause them to switch their attention to the previously unattended message.  Moray concluded that only “important” material can penetrate the filter set up to block unattended messages.  Participants did not always hear their name in the unattended channel: When not cued in advance to be vigilant, only 33% of the participants ever noticed their names.  Alternative explanation for the name recognition finding is that the shadowing task does not always take 100% of one’s attention.  Attention occasionally lapses and shifts to the unattended message. During these lapses, name recognition occurs. - Treisman (1960) Effect of semantics/ Attentional Leakage  She played participants two distinct messages, each presented to a different ear, and asked the participants to shadow one of them. At a certain point in the middle of the messages, the content of the first message and the second message was switched so that the second continued the story-line of the first and vice versa.  Immediately after the two messages “switched ears”, many participants reported one or two words from the “unattended ear”.  Treisman reasoned that participants might be basing their selection of which message to attend to at least in part on the meaning of the message – a possibility that filter theory does not allow for. - Wood and Cowan (1995)  Participants perform a dichotic listening task. Two of the groups shadowed an excerpt from The Grapes of Wrath (read very quickly, at a rate of 175 words/minute) in the attended channel (always presented to the right ear) and were presented with an excerpt from 2001: A Space Odyssey in the unattended channel.  Five minutes into the task, the speech in the unattended channel switched back to backward speech for 30 seconds.  Two groups differed only in how long the “normal” speech was presented after the backward speech: 2 ½ minutes for one group; 1 ½ minutes for the other.  Third control group of participants heard an unattended message with no backward speech.  Wood and Cowan first asked whether the people who noticed the backward speech in the unattended message showed a disruption in their shadowing of the attended message.  The answer was a clear yes.  Wood and Cowan counted the percentage of errors made in shadowing and noted that the percentage rose to a peak during the 30 seconds of the backward-speech presentation.  Effect was especially dramatic for those people who reported noticing the backward speech.  Participants who did report hearing backward speech made noticeably more errors, which peaked 10 to 20 seconds after the backward speech began.  Control participants showed no rise in their shadowing errors, nor did most of the participants who did not report noticing the backward speech.  Wood and Cowan concluded that the attentional shift to the unattended message was unintentional and completed without awareness.  Based this conclusion on the facts that detection of the backward speech interrupted and interfered with shadowing and that error rates peaked in a uniform time for all participants who noticed the backward speech.  Believed that the participants who noticed the backward speech had their attention “captured” by the backward speech, which led to poorer performance on the main shadowing task. - Conway, Cowan, and Bunting (2001) showed that research participants who detect their name in the unattended message are those who have a lower working-memory span.  20% of participants with high working-memory spans detected their names in the unattended channel, compared with 65% of participants with low working-memory spans.  A lower working-memory capacity means less ability to actively block the unattended message.  People with low working-memory spans are less able to focus. Attenuation Theory - Proposed by Anne Treisman (1960)  Instead of considering unattended messages completely blocked before they could be processed for meaning (as in filter theory), Treisman argued that their “volume” was “turned down.” [Some meaningful information in unattended messages might still be available, even if hard to recover] - Incoming messages are subjected to three kinds of analysis: 1. The message’s physical properties, such as pitch or loudness 2. Linguistic, a process of parsing the message into syllables and words 3. Semantic, processing the meaning of the message. - Words that have subjective importance (such as your name) or that signal danger (“Fire!” “Watch out!”) have permanently lower thresholds  they are recognizable even at low volumes  Words or phrases with permanently lower thresholds require little mental effort by the hearer to be recognized. - The context of a word in a message can temporarily lower its threshold.  If a person hears “The dog chased the…,” the word cat is primed – that is, especially ready to be recognized.  Even if the word cat were to occur in the unattended channel, little effort would be needed to hear and process it.  Hearing the previous words in a sentence primed the participants to detect and recognize the words that followed, even when those words occurred in the unattended message. - According to Treisman (1964), people process only as much as is necessary to separate the attended from the unattended message.  If the two messages differ in physical characteristics, then we process both message only to this level and easily reject the unattended message.  If the two messages differ only semantically, we process both level of meaning and select which message to attend to based on this analysis.  Processing for meaning takes more effort  Messages not attended to are not completely blocked but rather weakened in much the way that turning down the volume weakens an audio signal from a stereo.  Parts of the message with permanently lowered thresholds (“significant” stimuli) can still be recovered, even from unattended messages. Attenuation Theory Filter Theory • Allows for many • Allows for only one different kinds of kind of analysis for all analyses of all messages messages • Unattended • Unattended messages messages, once are weakened but the processed for physical informatio they characteristics, are contain is still discarded and fully available. blocked. Late-Selection Theory - Proposed by Deutsch and Deutsch (1963) and later elaboarated and extended by Norman (1968)  Theory holds that all messages are routinely processed for at least some aspects of meaning.  Attentional selection occurs after this routine processing. - Filter theory hypothesizes a bottleneck – a point at which the processes a person can bring to bear on information are greatly limited – at the filter. - Late-selection theory also describes a bottleneck, but locates it later in the processing, after certain aspects of the meaning have been extracted.  All material is processed up to this point, and information judged to be most “important” is elaborated more fully. This elaborated material is more likely to be retained; unelaborated material is forgotten. - Message’s “importance” depends on many factors, including its context and the personal significance of certain kinds of content.  Also relevant is the observer’s level of alertness: At low levels of alertness (such as when we are asleep), only very important messages (such as the sound of our newborn’s cry) capture attention.  At higher levels of alertness, less important messages (such as the sound of a television program) can be processed. - Attentional system functions to determine which of the incoming messages it’s the most important; this message is the one to which the observer will respond. Attention, Capacity and Mental Effort - Bottle neck Analogy: The smaller diameter of the bottle’s neck relative to the diameter of the bottle’s bottom reduces the rate at which liquid can pass through. The wider the neck, the faster the contents can pass through. - Daniel Kahneman (1973) viewed attention as a set of cognitive processes for categorizing and recognizing stimuli.  The more complex the stimulus, the harder the processing, and therefore the more attentional resources are required.  People have some control over where they direct their mental resources, however: they can often choose what to focus on and where to allocate their attentional resources.  Many factors influence this allocation of capacity, which itself depends on the extent and type of mental resources available.  The availability of mental resources, in turn, is affected by the overall level of arousal, or state of alertness. - Kahneman argued that one effect of being aroused is that more cognitive resources are available to devote to various tasks.  The level of arousal also depends on a task’s difficulty.  We are less aroused while performing easy asks, than we are when performing more difficult tasks.  We bring fewer cognitive resources to easy tasks, which, fortunately, require fewer resources to complete. - Arousal affects our capacity (the sum total of our mental resources) for tasks. - Allocation policy is affected by an individual’s enduring dispositions, momentary intentions, and evaluation of the demands on one’s capacity  We pay more attention to things we are interested in, are in the mood for, or have judged important. - In Kahneman’s view, attention is part of what the layperson would call “mental effort.” The more effort expended, the more attention we are using. - Greater effort or concentration results in better performance on some tasks- those that require resource-limited processing, performance of which is constrained by the mental resources or capacity allocated to it. (Example, taking a midterm) - On some other tasks, one cannot do better no matter how hard one try.  Example: Trying to detect a dim light or a soft sound in a bright and noisy room.  Even if you concentrate as hard as you can on such a task, your vigilance still may not help you detect the stimulus  Performance is said to be data limited, meaning that it depends entirely on the quality of the incoming data, not on mental effort or concentration.  Automaticity and the Effects of Practice - Over time, the attentional capacity required for a given task decreases. - What affects the capacity a task requires?  The difficulty of the task  Individuality’s familiarity with the task  Practice is thought to decrease the amount of mental effort a task requires The Stroop Effect - A series of colour bars or colour words printed in conflicting colours. - Participants were asked to name, as quickly as possible, the ink colour of each item in the series.  When shown bars, they did so quickly, with few errors and apparently little effort.  When the items consisted of words that named colours other than that of the ink in which the item was printed, participants stumbled through these lists, finding it difficult not to read the word formed by the letters. - Automatic  one that requires no attention and cannot be inhibited. - The most common theoretical account of the Stroop effect is that for literate adults reading is automatic, and its products, which conflict with the ink colour on a Stroop trial, interfere with a participant’s ability to name the ink colour. Automatic versus Attentional (Controlled) Processing - Posner and Snyder (1975) offered three criteria for cognitive processing to be called automatic processing: (1) it must occur without intention; (2) it must occur without involving conscious awareness; (3) it must not interfere with other mental activity. - Schneider and Shiffrin (1977) examined automatic processing of information under well- controlled laboratory conditions  Asked participants to search for certain targets, either letters or numbers, in different arrays of letters or numbers called frames  Example: A participant might be asked to search for the target J in an array of four letters: B M K T (Note: this trial is “negative”, in the sense that the target is not present in the frame.)  Previous work had suggested that when people search for targets of one type (such as numbers) in an array of a different type (such as letters), the task is easy.  Numbers against a background of letters seem to “pop out” automatically.  The number of nontarget characters in an array, called distractors, makes little inference if the distractors are of a different type from the targets.  Finding a specific letter against a background of other letters seems much harder.  Searching for J among the stimuli R J T, is easier than searching for the J among the stimuli G K J L T, both of which are more difficult than finding a J amongst digits  When the target and the distractors are of the same type, the number of distractors does make a difference.  Two conditions in the experiment:  Varied-mapping condition  Set of target letters or numbers, called the memory set, consisted of one or more letters or numbers, and the stimuli in each frame were also letters or numbers. Targets in one trial could become distractors in subsequent trials.  The task was expected to be hard and to require concentration and effort.  Consistent-mapping condition  Target memory set consisted of numbers and the frame consisted of letters, or vice versa. Stimuli that were targets in one trial were never distractors in other trials.  The task was expected to require less capacity.  In addition, experimenters varied three other factors to manipulate the attentional demands of the task  Frame size- the number of letters and numbers presented in each display  Number was always between 1 and 4  Slots not occupied by a letter or number contained a random dot pattern.  Frame time – the length of time each array was displayed  Varied from ~ 20 milliseconds to 800 milliseconds.  Memory set- the number of targets the participant was asked to look for in each trial.  In the consistent mapping condition, thought to require only automatic processing (because the targets and distractors were not the same type of stimuli), participants’ performance varied only with the frame time, not with the number of targets searched for (memory set) or the number of distractors present (frame size)  Participants were just as accurate in searching for one as for four targets and in searching among one, two, or four items in a frame. Accuracy depended only on the length of time the frames were displayed.  In the varied-mapping condition, thought to require more than automatic processing (because the targets and distractors could both be letters, or both numbers, and because targets on one trial could become distractors on another), participants’ performance in detecting the target depended on all three variables: memory set size, frame size, and frame time.  Distinguished two kinds of processing:  Automatic processing  Used for easy tasks, and with familiar items  Operates in parallel (meaning it can operate simultaneously with other processes)  Does not strain capacity limitations  Occurred in the consistent-mapping condition  Controlled Processing  Used for difficult tasks and ones that involve unfamiliar processes  Operates serially (with one set of information processed at a time)  Requires attention  Capacity limited  Under conscious control  Use with non-routine or unfamiliar tasks.  Occurred in the varied-mapping condition  Divided Attention - Divided Attention: the ways in which a cognitive processor allocates cognitive resources to two or more tasks that are carried out simultaneously Dual-Task Performance - Spelke, Hirst and Neisser (1976) study  Two Cornell University students were recruited as participants. Five days a week, for 17 weeks, working in 1 hour sessions, these students learned to write words dictated while they read short stories. Their reading comprehension was periodically tested.  After 6 weeks of practice, their reading rates approached their normal speeds.  By the end of 6 weeks, their scores on the reading comprehension tests were comparable whether they were only reading stories (and thus presumably giving the reading task their full attention) or reading stories while writing down dictated words.  Further investigation revealed that participants could also categorize the dictated words by meaning and could discover relations among the words without sacrificing reading speed or comprehension. -
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