Week 6 Lecture Notes.pdf

Indian Institute of Technology Kanpur In Collaboration with National Program on Technology Enhanced Learning (NPTEL) Presents Course Title: Basic Cognitive Processes By: Dr. Ark Verma, Assistant Professor of Psychology, Department of Humanities & Social Sciences, IIT Kanpur Lecture 25: AOention - II Selective AOention it often happens in public gatherings like in parties or restaurants etc.; that some other ongoing conversations than the one you are currently involved in grabs our aOention. Colin Cherry (1953) referred to this phenomenon as the cocktail party eﬀect, i.e. the process of tracking one conversation in the face of the distractions from other conversations. Cherry observed that cocktail parties are often seOings in which selective aOention is salient. Cherry studied selective aOention in a carefully controlled experimental seOing; task known as shadowing. In shadowing, one listens to two diﬀerent messages. Cherry presented a separate message to each ear; known as dichotic presentation; and asked the participants to repeat back only one of the messages as soon as possible after hearing it. Cherry’s participants were quite successful in shadowing distinct messages in dichotic listening tasks, although such shadowing required a signiﬁcant amount of concentration. Image: Sternberg & Sternberg (2011) Cognitive Psychology. Wadsworth Publishing. 9th ed. ( p. 149). The participants were also able to notice physical, sensory changes in the unaOended message - for example, when the message was changed to a tone or the voice changed from a male to female voice. However, they did not notice they semantic changes in the unaOended message. They also failed to notice even when the unaOended message shifted from English to German or was played backward. Conversely, about 1/3 of the people, when their name is presented during these situations shifted their aOention to their name. Some researchers have noticed that those who hear their name in the unaOended message have limited working memory capacity & are thus easily distracted (Conway, Cowan & Bunting, 2000). Three factors could help one to selectively aOend the target speaker, if you are caught in a busy restaurant among many conversations: o distinctive sensory characteristics of the target’s speech. e.g. high vs low pitch, pacing & rhythm. o sound intensity (loudness) o location of the sound source (Brungard & Simpson, 200&0. Theories of Selective A9ention o The theories of selective aOention can be grouped into ﬁlter & bo9leneck theories. A ﬁlter blocks some of the information going though and thereby selects only a part of the total information to pass through the next stage. A boOleneck slows down information passing through. Two questions: o Whether there is a distinct ﬁlter for incoming information? o Where in the processing does ﬁltering occur, Early or Late? Broadbent’s Model: Acc. to one of the earliest theories of aOention, we ﬁlter information right after we notice it at the sensory level (Broadbent, 1958). Multiple channels of sensory input reach an aOentional ﬁlter; those channels can be distinguished by their characteristics like loudness, pitch, or accent. The ﬁlter permits only one channel of sensory information to proceed and reach the process of perception. We thereby assign meaning to our sensations. Other stimuli will be ﬁltered out at the sensory level and may never reach the level of perception. Broadbent’s theory was supported by Colin Cherry’s ﬁndings that sensory information sometimes may be noticed by an unaOended ear if it does not have to be processed elaborately (e.g. voice shifts to tone); but information requiring higher perceptual processes is not noticed if not aOended to (e.g. English shifts to German). Selective Filter Model: Moray found that even when participant’s ignore most other high level aspects of an unaOended message, they frequently still recognise their names in an unaOended ear (Moray, 1959). He suggested that the reason for this eﬀect is that messages that are of high importance to a person may anyways breakthrough the ﬁlter of selective aOention; though other messages may not. To modify Broadbent’s metaphor, one could say that, according to Moray, the selective ﬁlter blocks out most information at the sensory level; but some personally relevant information can still burst through. A9enuation Model: Treisman explored why some unaOended messages pass through the ﬁlter by conducting some experiments. She had participants shadowing coherent messages, and at some point, switched the remainder of the message to the unaOended ear. Participants picked up the ﬁrst few words of the message they had been shadowing in the unaOended ear (Treisman, 1960); so they somehow must have been somehow processing the content of the unaOended message. Moreover, if the unaOended message was identical to the amended one; all participants notice it. They noticed even if one of the messages was slightly out of temporal synchronisation with the other. Trainman also observed that some ﬂuently bilingual participants noticed the identity of the messages if the unaOended message was a translated version of the aOended one. Her ﬁndings suggested that at least some information about unaOended signals is being analysed. Treisman proposed a theory of selective aOention that involves a later ﬁltering mechanism. Instead of blocking stimuli out, the ﬁlter merely weakens the strength of the stimuli other than the target stimulus. So, when stimuli reach us, we analyse them at a low level for target properties like loudness & pitch; if the stimuli process those target properties, we pass the signal on to the next stage; if they do not posses the target properties a weakened version is passed on to the next stage. In a next step, we perceptually analyse the meaning of the stimuli and their relevance to us, so that even a message from the unaOended ear that is supposedly irrelevant can come into awareness and inﬂuence actions if it has some meaning for us. Image: Sternberg & Sternberg (2011) Cognitive Psychology. Wadsworth Publishing. 9th ed. ( p. 150). Late - Filter Model: Deutsch & Deutsch (1963) developed a model in which the location of the ﬁlter is even later. They suggested that stimuli are ﬁltered out only after they have been analysed for both their physical properties and their meaning. This late ﬁltering would allow people to recognise information entering the unaOended ear. for e.g. they might recognise the sound of their own names or a translation of the aOended version. Image: Sternberg & Sternberg (2011) Cognitive Psychology. Wadsworth Publishing. 9th ed. ( p. 152). A synthesis: o Ulric Neisser synthesised the early ﬁlter and the late ﬁlter models and proposed that there are two processes governing selective aOention: Pre a9entive Processes: These automatic processes are rapid & occur in parallel. They can be used to notice only physical sensory characteristics of the unaOended message; but they do not discern meanings. A9entive, controlled processes: These processes occur later. They are executed serially and consume time and aOentional resources, such as working memory. They can cue used o observe relationships among features; synthesise fragments into mental representation of an object. This two - step model could easily account fro Cherry’s, Moray’s, & Treisman’s data. Also, this model nicely incorporates aspects of Treisman’s signal aOenuation theory & her feature integration theory. Acc. to Treisman, discrete processes for feature detection & for feature integration occur during searches. Neuroscience of selective a9ention o Hillyard & colleagues (1973) conducted a ground - breaking study, exposing participants to two streams of tones; one in each ear. o Participants were asked to detect occasionally occurring target stimuli; when the target stimuli occurred in the aOended ear, the ﬁrst negative component of the ERP was larger than when the target occurred in the unaOended ear. The N1 wave is a negative wave appearing about 90ms after the onset of the target stimulus, o The researchers hypothesised that the N1 wave was a result of the enhancement of the target stimulus. At the same time here was a suppression of the other stimuli(distracters). This result is consistent with the ﬁlter theories of aOention. Later studies (Woldorﬀ et al., 1993) found an even earlier reaction to the target stimulus in the form of a positive wave that occurs about 20 - 50ms after the onset of the target. This wave originates in the Heschl’s gyro, located in the auditory cortex. Similar eﬀects have also been found for visual aOention. o If a target stimulus appears in an unaOended region of the visual ﬁeld, the occipital P1is larger than when the target appears in an unaOended region (Van Voorhies & Hillyard, 1977). To Sum Up References Sternberg & Sternberg (2011). Cognitive Psychology. Wadsworth Publishing. 6th Ed. Indian Institute of Technology Kanpur In Collaboration with National Program on Technology Enhanced Learning (NPTEL) Presents Course Title: Basic Cognitive Processes By: Dr. Ark Verma, Assistant Professor of Psychology, Department of Humanities & Social Sciences, IIT Kanpur Lecture 26: AOention - III Divided AOention Investigating Divided A.ention in the Lab o One of the early works in the area of divided aOention had participants view a videotape in which the display of a basketball game on the display of a hand slapping game. o Participants could successfully monitor one activity and ignore the other; but they had great diﬃculty in monitoring both activities at once; even if the basket ball game was watched by one eye & the hand - slapping game by the other eye (Neisser & Becklen, 1975). o Neisser & Becklen hypothesised that the improvement in performance would have occurred as a result of practice & also that the performance of multiple tasks was based on skill resulting from practice. the following year, investigators used a dual - task paradigm to study divided aOention during the simultaneous performance of two activities: reading short stories and writing down dictated words (Spelke et al., 1976). the researchers would compare and contrast the response times and accuracy of performance in each of the three conditions. As expected, initial performance was quite poor for the two tasks, when they had to be performed at the same time. However, Spelke & colleagues had their participants practice to perform these two tasks 5 days a week for many weeks (85 sessions in all). To the surprise of many, the performance improved on both tasks after practice. o They showed improvements in their speed of reading and accuracy of reading comprehension, as measured by comprehension tests; also, they showed increases in their recognition memory for words they had wriOen during dictation. o Eventually, participants performance on both tasks reached the same levels as when the participants had performed the tasks alone. They soon could perform both the tasks at the same time without a loss in performance. Speke and colleagues suggested that these ﬁndings showed that controlled tasks can be automatised so that they consume fewer aOentional resources. Also, two discrete controlled tasks may be automatised to function together as a unit. However, they still continue to be intentional & conscious and involve high levels of cognitive processing. A rather diﬀerent approach to study divided aOention involves focussing on extremely simple tasks that require speedy responses. When people try to perform two overlapping speeded tasks, the responses for one or both tasks are almost always slower (Pashler, 1994). When a second task begins soon after the ﬁrst task has started, speed of performance usually suﬀers; the slowing resulting from simultaneously engagement in speeded tasks; called the psychological refractory period eﬀect, also called aOentional blink. Image: Amador-Campos, Casanova, Bezerra, Torro-Alves & Sanchez (2015). AOentional Blink in Children With AOention deﬁcit Hyperactivity Disorder. Revista Brasileira de Psiquiatria. 37 (2). Findings form PRP studies indicate that people can accommodate fairly easily perceptual processing of the physical properties of sensory stimuli when engaged in a second speeded task (Miller et al., 2009). However, they cannot readily accomplish more than one cognitive task requiring them to choose a response, retrieve information from memory, or engage in various other cognitive operations; one or both the tasks will show the PRP eﬀect. Theories of Divided A.ention o a number of researchers have developed capacity models of aOention to understand our ability to divide our aOention. o these models explain how we can perform more than one aOention - demanding task at a time. they posit that people have a ﬁxed amount of aOention that they can choose to allocate according to what the task requires. o there are two diﬀerent kinds: one kind of model suggests that there is one single pool of aOentional sources that can be divided freely, and the other model suggests that there are multiple sources of aOention. Image: Sternberg & Sternberg (2011). Cognitive Psychology. Wadsworth Publishing. 6th Ed.(p. 156) it now appears that such models represent an oversimpliﬁcation. people are much beOer at dividing their aOention when competing tasks are in diﬀerent modalities. at least some aOentional resources may be speciﬁc to the modality (e.g. verbal or visual) in which a task is presented. for example: most people easily can listen to music and concentrate on writing simultaneously (the two being diﬀerent tasks modality - wise). But it is harder to listen to the news station and concentrate on writing at the same time. because both are verbal tasks. Similarly two visual tasks are more likely to interfere with each other than are a visual task coupled with an auditory one. aOentional resources theory has been criticized heavily as being overly broad & vague (Navon, 1984). Resource theory seems to be a beOer metaphor for explaining the phenomenon of divided aOention on complex tasks. in these tasks, practice eﬀects may be observed. Acc. to this metaphor, as each of the complex tasks becomes increasingly automatized, performance of each task makes fewer demands on limited capacity aOentional resources. Factors that Inﬂuence Our Ability to Pay A.ention o There are many other variables that have an impact on our ability to concentrate and pay aOention: Anxiety: Being anxious, either by nature (trait - based anxiety) or by situation,(state - based anxiety) places constraints on aOention (Reinholdt - Dunne et al., 2009). Arousal: One’s overall state of arousal aﬀects aOention; being drowsy or drugged limits aOention while being excited sometimes enhances aOention (MacLean et al., 2009). Task Diﬃculty: Task diﬃculty particularly inﬂuences performance during divided aOention. Skills: The more practiced & skilled one is in performing a task, the more one’s aOention is enhanced (Spelke et al., 1976). Neuroscience of A.ention: o Acc. to Michael Posner, the aOentional system in the brain “is neither a property of a single brain area nor of the entire brain” (Posner & Dehaene, 1994). o Posner & Mary Rothbart in 2007, conducted a series of neuroimaging studies in the area of aOention to investigate whether the many diverse results of studies conducted pointed to a common direction. o They found that what at ﬁrst seemed like an unclear paOern of activation could be eﬀectively organised into areas associated with the three sub - functions of aOention: alerting, orienting, and executive aOention. Alerting: Alerting is deﬁned as being prepared to aOend to some incoming event, and maintaining this aOention. Alerting also includes the process of geOing to this state of preparedness. o The brain areas involved in alerting are the right frontal and parietal cortices as well as the locus coeruleus. The neurotransmiOer norepinephrine is involved with the maintenance of alertness. If the alerting system does not work properly, people may develop symptoms of ADHD; in the process of regular raging dysfunctions of the alerting system may develop as well. Orienting: orienting is deﬁned as the selection of stimuli to aOend to. This kind of aOention is needed when we perform visual search. The orienting network develops during the ﬁrst year of life. o The brain areas involved in the orienting network are the superior parietal lobe, the temporal parietal junction, the frontal eye - ﬁelds, & the superior colliculus. The modulating neurotransmiOer is acetylcholine. o Dysfunction with this system has been associated with autism. Executive A.ention: executive aOention includes processes for monitoring and resolving conﬂicts that arise among internal processes. These processes include thoughts, feelings, and responses. o The brain areas involved in this highest order of aOentional processes are the anterior cingulate, lateral ventral, and prefrontal cortices; as well as the basal ganglia. The neurotransmiOer most involved in executive aOention is dopamine. o Dysfunction within this system is associated with Alzheimer’s disease, borderline personality disorder, and schizophrenia. Goldstein (2010). Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. (p. 109). Distractions While Driving Driving is one of the tasks that require constant aOention; not being able to do the same due to fatigue or involvement in other tasks can have disastrous consequences. o in a naturalistic driving study (Dingus et al., 2006) video recorders in 100 vehicles documented records of both, what the drivers were doing & the outside view. o they found that in more than 80% (of 82) of the crashes & 67% (of 771) of the near crashes the driver was inaOentive in some way 3 seconds before the crash. In a laboratory experiment on the eﬀects of cell phones, Strayer, William & Johnston (2001) placed participants in a simulated driving task that required them to apply the brakes as quickly as possible in response to a red light. Doing this task while talking on a cell phone caused participants to miss twice as many of the red lights as when they weren’t talking on the phone & also increased the time it took them to apply the brakes. Goldstein (2010). Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. (p. 94). Strayer & Johnston concluded from this result that talking on the phone uses cognitive resources that would otherwise be used for driving the car (other studies include, Haringey & Western, 2001; Lamble et al., 1999; Spence & Read, 2003; Violanti, 1998) To Sum Up. References Sternberg & Sternberg (2011). Cognitive Psychology. Wadsworth Publishing. 6th Ed. Goldstein E. b. (2010). Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Indian Institute of Technology Kanpur In Collaboration with National Program on Technology Enhanced Learning (NPTEL) Presents Course Title: Basic Cognitive Processes By: Dr. Ark Verma, Assistant Professor of Psychology, Department of Humanities & Social Sciences, IIT Kanpur Lecture 27: AOention - IV AOention and Visual Perception Ina$entional Blindness: Mack & Rock (1998) created a situation in which a person’s aOention is focused on one task and then determined whether the person perceived an easily visible nearby stimuli. The observer’s task was to indicate which arm of the cross was longer, the horizontal arm or the vertical arm. Then, on one trial, a small test object, which was within the observer's ﬁeld of clear vision, was added to the display. When observers were then given a recognition test in which they were asked to pick the object that had been presented, they were unable to do so. Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 95) Paying aOention to the vertical and horizontal arms apparently made observers “blind” to the unaOended test object. The phenomenon is termed ina$entional blindness. Mack & Rock demonstrated inaOention blindness using rapidly ﬂashed geometrical stimuli; but other research has shown that similar eﬀects can be achieved in more natural scenarios as well. Simons & Chabris (1999) created a situation in which one part of a scene is aOended and the other is not. They created a 75 second ﬁlm that showed two teams of 3 players each; & the one in white passing a basketball around. The other dressed in black was not handling the ball. Observers were told to count the number of passes, a task that focused their aOention on the team in white. After about 45s, an event that took 5 seconds occurred, i.e. one of these events was a person dressed in a gorilla suit, walking through the scene. After seeing the video, observers were asked whether they had seen anything unusual happen or whether they see more than six players. Nearly half - 46% - of the observers failed to report having seen the event, even though it was clearly visible. Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 95) Further … Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 96) Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 97) Change Detection: Could you detect the change in the picture? o Rensink & colleagues did a similar experiment; where the pictures were alternated in the same way until observers were able to determine what was diﬀerent about the two pictures and found that the pictures had to be alternated back & forth a number of times before the diﬀerence was detected. o This diﬃculty in detecting changes in scenes is called change blindness (Rensink, 2002). o But when Rensink added a cue indicating which part of the scene had been changed, participants detected the changes much more quickly (Rensink, 2002). It’s not always we miss out on such changes in the environment, there are cues to help us orient aOention to such stimuli in the environment. These cues automatically aOract our aOention & increase the detection accuracy & speed. Automatic aOraction of aOention by a sudden visual or auditory stimulus is called exogenous a$ention. AOentional orientation that occurs when one consciously decides to scan the environment, to ﬁnd a speciﬁc stimulus or just to track the environment is called endogenous a$ention. Both these types of aOention can involve overt a$ention, i.e. shifting aOention by moving the eyes (Carrasco, 2010). Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 99) Overt AOention with Eye – Movements In order to look for Dylan’s face, you would have had to move your eyes across the picture from face to face to see each one clearly. The shifting of eyes can be measured by using a device called an eye tracker, which tracks the movement of the eyes from one pint to another. Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 100) the small dots indicate ﬁxations, places where the eyes brieﬂy paused. the lines indicate saccadic eye - movements, i.e. movement of the eye from one ﬁxation to the next. Typically, people make about 3 ﬁxations per second when viewing an unfamiliar scene. Two kinds of factors determine how people shift their aOention by moving their eyes: o bo$om - up, based primarily on the physical characteristics of the stimulus & o top - down, based on the relation between the observer and the scene - i.e. what the person knows about the scene and the demands of a task that involves the objects in the scene. Top - Down Determinants Scene Schemas - an obserever’s knowledge about what is contained in physical scenes. o For e.g. when Vo & Henderson (2009) showed observers pictures like the ones (next slide), observers looked longer at the printer than the pan. Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 100) Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 100) the fact that people look longer at things that seem out of place in a scene means that aOention is being aﬀected by their knowledge of what is usually found in the scene. Covert AOention: Without Eye - Movements Covert A$ention has been studies using a procedure called pre cueing, in which the participant is presented with a cue that indicates ahwer stimulus is most likely to appear. Pre cueing has been used to study two kinds of aOention: Location - Based A$ention: Michael Posner & colleagues were interested in answering the following question: Does aOention to a speciﬁc location improve our ability to respond rapidly to a stimulus presented at that location? Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 102) Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 102) The results of the experiment indicate that observers reacted more rapidly on valid trials than on invalid trials, leading to the conclusion that information processing is more eﬀective at the place where aOention is directed. These & similar results gave rise to the idea that aOention is like a spotlight lens that improves processing when directed towards a particular location (Marino & Scholl, 2005). Object - Based A$ention: Experiments have also shown that aOention can also be associated with speciﬁc objects. Experiments studying object - based aOention have shown that when aOention is directed to one place on an object, the enhancing eﬀect of this aOention spreads throughout the object.. o For e.g. Egly et al., (1994) asked participants to keep their eyes on the +, then one end of the rectangle was brieﬂy highlighted. This was the cue signal that indicated where a target, a dark square would appear. The participant’s task was to press a buOon when the target appeared anywhere on the display. Reaction Times were fastest when the target appeared where the cue signal predicted it would appear. However, the most important ﬁnding is that participants responded faster when the target appeared within the same rectangular object location B than when it appeared at another location C. Note that B & C are same distance from A. Apparently, the enhancing eﬀect of aOention had spread within the rectangle, so even though the cue was at A, some enhancement occurred at B as well, this is the same object advantage. Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 103) Location and Object Based AOention Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 103) Image: E. B. Goldstein, Cognitive Psychology_ Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Fig. 4.17., (p. 103) To Sum Up References E.B. Goldstein (2010). Cognitive Psychology Connecting Mind, Research and Everyday Experience. Wadsworth Publishing. 3rd Ed. Indian Institute of Technology Kanpur In Collaboration with National Program on Technology Enhanced Learning (NPTEL) Presents Course Title: Basic Cognitive Processes By: Dr. Ark Verma, Assistant Professor of Psychology, Department of Humanities & Social Sciences, IIT Kanpur Lecture 29: Memory - I Memory “Has it ever struck you…that life is all memory, except for the one present moment that goes by so quickly you hardly catch it going? It’s really all memory except for each passing moment.” – Tennessee Williams What is Memory? o memory is the processes involved in retaining, retrieving, & using information about stimuli, images, events, ideas, & skills after the original information is no longer present. An interestig case of Clive Wearing: Excerpt from: Goldstein (2010). Cognitive Psychology: Connecting Mind, research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (p.117). Let us try and structure memory: o Present (this moment, the moment just passed) o Past (that moment, that one ) o Long Past (those moments that passed sometime back) Ok..make it simple: o Sensory + Short - term + Long - term Memory!!! Image: Goldstein (2010). Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. (p. 118) Richard Atkinson & Richard Shiﬀrin (1968) proposed one of the earliest models in memory, called the modal model of memory because it included many of the features of memory models of the 1960s. This model became extremely inﬂuential and shaped research on memory for years. The stages in the model are called the structural features. They are: o sensory memory an initial stage that holds all incoming information for seconds or fractions of seconds. o short - term memory holds 5-7 items for about 15 - 30 seconds. o long - term memory can hold a large amount of information of information for years or decades. Atkinson & Shiﬀrin also described the memory system as including control processes, which are active processes that can be controlled by the person and may diﬀer from one task to another. e.g. rehearsal - repeating a stimulus over and over, as one might repeat a telephone number in order to hold it in one’s mind after looking it up in the phone book. let’s see how it works… o if Rachel has to look up a pizzeria over internet to order Pizza. o when she ﬁrst looks at the screen, all of the information that enters her eyes is registered in the sensory memory; she uses the control process of selective a6ention to focus on a number, so the number enter’s short term memory. o She knows she might need the number again, so she decides that in addition to storing the number in her phone, she is going to memorise the number. the process she uses to memorise or store the number is called encoding. o a few days later, she wants to order Pizza again, so she retrieves the number again from long term memory. Image: Goldstein (2010). Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. (p. 119) Image: Goldstein (2010). Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. (p. 119) Sensory Memory Sensory Memory is the retention, for brief periods of time, of the eﬀects of sensory stimulation. e.g. the moving sparkler & the experience of seeing a ﬁlm. Image: Goldstein (2010). Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. (p. 120) as you swing the sparkler through the air, creating a trail of light; you would realise that there is actually no light along this trail. The lighted trail for the most part, is a creation of your own mind. this retention of the perception of light in your mind is called the persistence of vision. Similarly, once you are watching a movie in a darkened theatre, you may see actions moving smoothly across the screen; but what is actually projected is quite diﬀerent. ﬁrst, a single frame is positioned in the front of the projector lens, and when the projector’s shuker opens, the image on the ﬁlm frame ﬂashes on the screen. the shuker then closes, so the ﬁlm can move to the next frame & during the time the screen is dark. when the next frame has arrived in front of the lens, the shuker reopens, ﬂashing the next image on to the screen. this process is repeated rapidly, around 24 times per second; so 24 images are ﬂashed on the screen every second separated by a brief period of darkness. a person viewing the ﬁlm does not see the dark intervals between the images because the persistence of vision ﬁlls in the darkness by retaining the image of the last frame. Sperling’s Experiment! o George Sperling (1960) wondered how much information people can take in from brieﬂy presented stimuli. He determined this in a famous experiment in which he ﬂashed an array of lekers, on the screen for 50ms and asked his participants to report as many of the lekers as possible. o this part of the experiment used the whole report method; when participants were asked to report as many lekers as possible from the whole matrix. o Given this task, participants were able to report an average of 4.5 lekers out of the 12 lekers. In the next version, Sperling devised the partial report method, i.e. he presented the matrix for 50 ms as before but sounded one of the following tones immediately after the matrix presentation, to indicate which row of lekers the participants were to report: High Pitched: Top Row Medium Pitched: Middle Row Low Pitched: Bokom Row because the tones were presented after the lekers were turned oﬀ, the participant’s akention was directed not to the actual lekers, which were no longer present but to whatever trace remind in the participant’s mind after the lekers were turned oﬀ. Image: Goldstein (2010). Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. (Fig. 5.5, p. 120) When the cue tones directed participants to focus their akention on one of the rows, they correctly reported an average of 3.3 of 4 lekers in that row. Sperling concluded that the correct description of what was happening was that immediately after the display was presented, participants saw an average of 82% of lekers in the whole display, but were not able to report all of these lekers because they rapidly faded as the initial lekers were being reported. Sperling then did an additional experiment to determine the time course of this fading. For this, Sperling devised a delayed partial report method in which the presentation of tones was delayed for a fraction of a second after the lekers were extinguished. The result of the delayed partial report method wa that when the cue tones were delayed for 1 second after the ﬂash, participants were able to report only slightly more than 1 leker in a row, the equivalent of about 4 lekers for all three rows - the same number of lekers they reported using the whole report method. Image: Goldstein (2010). Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. (Fig. 5.5, p. 120) Image: Goldstein (2010). Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. (Fig. 5.6, p. 122) Sperling concluded from these results that a short - lived sensory memory registers all or most of the information that hits our visual receptors, but that this information decays within less than a second. This brief sensory memory for visual stimuli is called the iconic memory and corresponds to the sensory memory stage of Atkinson & Shiﬀrin’s model. Other research using auditory stimuli, has shown that sounds also persist in the mind. This persistence of sound, which is called echoic memory, lasts for a few seconds after presentation of the original stimulus (Darwin et al., 1972). The sensory memory can register huge amounts of information, but it retains this information for only seconds or fractions of a second. Many cognitive psychologists believe that the sensory store is important for : o collecting information to be processed o holding the information brieﬂy while initial processing is going on & o ﬁlling in the blanks when the stimulation is intermikent. Sperling’s experiment is important not only because it reveals the capacity of sensory memory (large) & its duration (brief), but also because it provides yet another demonstration of how clever experimentation can reveal extremely rapid cognitive processes that we are usually unaware of. To Sum Up References Indian Institute of Technology Kanpur In Collaboration with National Program on Technology Enhanced Learning (NPTEL) Presents Course Title: Basic Cognitive Processes By: Dr. Ark Verma, Assistant Professor of Psychology, Department of Humanities & Social Sciences, IIT Kanpur Lecture 30: Memory - II Short - term Memory Short - term memory (STM) is the system involved in storing small amounts of information for a brief period of time (Baddeley et al., 2009). Duration of Short - Term Memory o Brown (1958), and Peterson & Peterson (1959) used the method of recall to determine the duration of STM. o In their experiments, participants were given a task similar to one here: Excerpt from: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Publishing Excerpt from: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (p. 124). Peterson & Peterson also did a similar experiment in which they varied the time between when they said the number and when the participant began recalling the leZers. Peterson & Peterson found that their participants were able to remember about 80% of the leZers after counting for 3 seconds but could remember an average of only 12% of the three leZer groups after counting for 18 seconds. They interpreted this result as demonstrating that participants forgot the leZers because of decay; i.e. their memory decayed because of the passage of time after hearing the leZers. However, when Keppel & Underwood (1962) looked more closely at the results, they found that if they considered the participant’s performance on just the ﬁrst trial, there was liZle fall - oﬀ between the 3 second & the 18 second delay. Why would memory worsen after a few trials? o Keppel & Underwood suggested that the drop - oﬀ in memory was due not to decay of the memory trace, Peterson & Peterson had proposed, but due to proactive interference - interference that occurs when information that was learned previously interferes with learning new information. Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.7, p. 125). Keppel & Underwood proposed that proactive interference is what caused the decrease in memory observed in the later trials of Peterson & peterson’s experiment. Thus recalling the early leZers in the list created interference that made it more diﬃcult to remember the later leZers in the list. Another illustration of proactive interference is when you try to remember new phone numbers of people who have just changed their number. Capacity of Short - term memory: there are certainly capacity limits on short - term memory as well. the estimates range between 4 - 9 items. Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (p. 125). According to the measurements of digit span, the average capacity of STM is about 5 - 9 items, i.e. about the length of a phone number. This idea was initially proposed by George Miller (1956) in a famous paper titled, “The Magical Number Seven, Plus or Minues Two”. More recent measures of STM capacity have set the capacity at about 4 items (Cowan, 2001). This conclusion was based on the results of experiments like the one by Luck & Vogel (1997), which measured the capacity of STM by ﬂashing two arrays of coloured squares separated by a brief delay. The participant’s task was to indicate whether the second array was the same or diﬀerent from the ﬁrst array. On trials in which the second row was diﬀerent, the colour of one square was changed Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.8, p. 126). Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.8, p. 126). Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.8, p. 126). The result of this experiment shows that performance was almost perfect when there were 1 to 3 squares in the arrays, but that performance began decreasing when there were more than 4 squares. Luck & Vogel (1997) concluded from this result that participants were able to retain about 4 items in their short - term memory. Other experiments, using verbal materials, have come to the same conclusion (Cowan, 2001). Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.8, p. 126). But 4 seems too less, or even 5 or 9, isn’t it? How do we store much more information that just these numbers? Chunking: Miller (1956) introduced the concept of chunking to describe the fact that small units (like words) can be combined to larger meaningful units, like phrases, or even larger units like sentences, paragraphs or stories. E.g. if I ask you to learn these words: monkey, child, wildly, zoo, jumped, city, ringtail, young. or these pairs: ringtail monkey, jumped wildly, young child, city zoo. or these sentence: The ringtail monkey jumped wildly for the young child at the city zoo. A chunk has been deﬁned as a collection of elements that are strongly associated with one another but are weakly associated with elements in other chunks (Cowan, 2001). e.g. ringtail monkey vs ringtail child. Thus, chunking in terms of meaning increases our ability to hold information in the STM. A similar demonstration is here: BCIFNCCASICB CIAFBINBCCBS Ericsson & colleagues (1980) demonstrated an eﬀect of chunking by showing how a college student with average memory ability was able to achieve amazing feats of memory. Their participant, S.F. had a typical memory span of 7 digits, after extensive training (230 one -hour sessions), he was able to repeat sequences of up to 79 digits without error. How? o S.F. used chunking to recode the digits into larger units that formed meaningful sequences. e.g. 3492, became 2 minutes and 49 point 2 seconds; near world record mile time. another similar example is based on the interaction between the STM & the LTM; provided by an experiment done by Chase & Simon (1973), wherein they showed chess players arrangements of chess pieces taken from actual games; for 5 seconds. the chess players were then asked to reproduce the positions they had seen. Chase & Simon compared the performance of a chess master who had played or studied chess for more than 10,000 hours to the performance of a beginner who had less than 100 hours of experience. the results show that the chess master placed 16 pieces out of 24 correctly on his ﬁrst try, compared to just 4/24 for the beginner. Also, the master required only 4 trials to reproduce all of the positions exactly, whereas the beginner could not do the same even after 7 trials. Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.9, p. 127). So, does the master have beZer STM than the beginners? Chase & Simon answered this question by testing the ability of masters & beginners to remember random arrangements of the chess pieces. When the pieces were arranged randomly, the familiar paZerns were destroyed, and the chess master’s advantage vanished. Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.9, p. 127). How is information coded in Short - term Memory? Coding refers to the way information is represented. determining how a stimulus is represented by the ﬁring of neurons is a physiological approach to coding. we can also take a mental approach to coding by asking how a stimulus or an experience is represented in the mind. There could be a variety of ways in which one can code information. Auditory Coding involves representing items in the STM based in their sound. o For e.g. in Conrad (1964)’s experiment, participants saw a number of target leZers which ﬂashed brieﬂy on a screen and were told to write down the leZers in order they were presented. o Conrad found that when participants made errors, they were most likely to misidentify the target leZer as another leZer that sounded like the target. e.g. “F” was often misidentiﬁed as “S” or “X”. Conrad concluded that the code for STM ia auditory, rather than visual. Visual Coding involves representing items visually, as would occur when remembering the details of a ﬂoor plan or the layout of streets on a map (Kroll, 1970). This use of visual codes in STM was demonstrated in an experiment by Sergio Della Sala and coworkers (1999), in which participants were presented with a task like: Della Sala found that participants were able to complete paZerns consisting of an average of 9 shaded squares before making mistakes. Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.10, p. 128). Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.13, p. 130). Semantic Coding is representing items in terms of their meaning. An example of semantic coding in STM is provided in an experiment by Wickens et al., (1976). On each trial, participants were presented with words related to either a fruit or profession. Participants in each group listened to three words for e.g. banana, peach, apple & then counted backwards for 15 seconds and then aZempted to recall all the three words. They did this for a total of 4 trials, with diﬀerent words presented on each trial. The basic idea behind this experiment was to create proactive interference, by presenting words in a series of trials from the same category. Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.11, p. 129). Results: o For the fruits group, one the ﬁrst trial the average percent recalled was 86%, but performance dropped on trials 2, 3,& 4 as additions names of fruits were presented. o The blue data points indicate the presence of proactive interference. o Evidence, that this interference can be aZributed to the meanings the words is provided by the results of the professions drop. As with fruits, performance is high on trial 1 & then drops on trials 2 & 3. But on trial 4, the names of fruits are presented; & because these are from a diﬀerent category, proactive interference is reduced & there is an increase in performance; this is called the release from proactive interference. Image: Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed. (Fig. 5.12, p. 130). References Goldstein (2010) Cognitive Psychology: Connecting Mind, Research & Everyday Experience. Wadsworth Publishing. 3rd Ed

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