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09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
09  sensation -perception
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09 sensation -perception

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  • Context السياق
  • Law of Proximity – The law of proximity states that when an individual perceives an assortment of objects they perceive objects that are close to each other as forming a group. For example, in the figure illustrating the Law of Proximity, there are 72 circles in total, but we perceive the collection of circles to be in groups. Specifically, we perceive there to be a group of 36 circles on the left side of the image, and three groups of 12 circles on the right side of the image. This law is often used in advertising logos to emphasize which aspects of events are associated
  • Law of Similarity – The law of similarity states that elements within an assortment of objects will be perceptually grouped together if they are similar to each other. This similarity can occur in the form of shape, colour, shading or other qualities. For example, the figure illustrating the law of similarity portrays 36 circles all equal distance apart from one another forming a square. In this depiction, 18 of the circles are shaded dark and 18 of the circles are shaded light. We perceive the dark circles to be grouped together and the light circles to be grouped together forming six horizontal lines within the square of circles. This perception of lines is due to the law of similarity.
  • Law of Closure – The law of closure states that individuals perceive objects such as shapes, letters, pictures, etc., as being whole when they are not complete. Specifically, when parts of a whole picture are missing, our perception fills in the visual gap. Research has shown that the purpose of completing a regular figure that is not perceived through sensation is in order to increase the regularity of surrounding stimuli. For example, the figure depicting the law of closure portrays what we perceive to be a circle on the left side of the image and a rectangle on the right side of the image. However, there are gaps missing from the shapes. If the law of closure did not exist, the image would depict an assortment of different lines with different lengths, rotations and curvatures, but with the law of closure, we perceptually combine the lines into whole shapes. [13] [14]
  • Law of Symmetry The law of symmetry states that the mind perceives objects as being symmetrical and forming around a center point. It is perceptually pleasing to be able to divide objects into an even number of symmetrical parts. Therefore, when two symmetrical elements are unconnected the mind perceptually connects them to form a coherent shape. Similarities between symmetrical objects increase the likelihood that objects will be grouped to form a combined symmetrical object. For example, the figure depicting the law of symmetry shows a configuration of square and curled brackets. When the image is perceived, we tend to observe three pairs of symmetrical brackets rather than six individual brackets.
  • Objects are perceived as lines that move along the smoothest path. Experiments using the visual sensory modality found that movement of elements of an object produce paths individuals perceive objects to be on. We perceive elements of objects to have trends of motion, which indicate the path that the object is on. The law of continuity implies the grouping together of objects that have the same trend of motion and are therefore on the same path. For example, if there are an array of dots and half the dots are moving upward while the other half are moving downward, we would perceive the upward moving dots and the downward moving dots as two distinct units.
  • The law of continuity states that elements of objects tend to be grouped together, and therefore integrated into perceptual wholes if they are aligned within an object. In cases where there is an intersection between objects, individuals tend to perceive the two objects as two single uninterrupted entities. Stimuli remain distinct even with overlap. We are less likely to group elements with sharp abrupt directional changes as being one object.
  • On this view, external objects are mind-independent, and we have direct access to them via our sensory organs. Simple." However, this view has several problems, which we will go over in detail in class, and which I will summarize briefly here: (1) In the meditations, Descartes pointed out that the senses sometimes deceive. There are illusions, hallucinations, etc. It would seem silly to deny this. Just place a pencil half-way in a glass of water or waggle that same pencil between your thumb and forefinger, simultaneously moving your hand up and down. In each case, the pencil will look bent, even though it isn't. But the above naive picture has no room for such perceptual deceptions. Put another way: if we perceive things directly, then how can we ever explain mis perception? (2) There is perceptual relativity and variability. What may look one way to you may look another way to another. Moreover, what may look one way to you at one time, may look another way to you at another. Colors, tastes, smells, feels, etc., can all vary from observer to observer, and can vary in the same observer at different times. If this is right, then which perspective is privledge? And how do we account, on the naive view, for the fact that some people have got it wrong, if there is a priveledged perspective? (3) Finally, in light of (1) and (2), how do we know for sure that there are these mind-independent objects out there? So, to accommodate the above sorts of objects, we might modify our Theory of Perception to the following...
  • On this view, external objects are still mind-independent. It's just that our access to them is mediated through our ideas of them. We have images in our head, as it were, and it is through these images that we get to figure out what is what in the world. This is why this view is called indirect realism: our access to mind-independent, external objects is indirect." However, this view has several problems, which we went over in class, and which I will summarize briefly here: (1) The relationship between external objects and ideas is incomprehensible. What sort of relationship would make sense in any case? How could we make sense of the relationship between external objects and our ideas? You might think that our ideas resemble or are simlar to or are like the external objects. Consider: How does a picture, a portrait, say, get to be about a particular somone? Well, first, the picture has to be like or resemble or be similar to the individual. In the above drawing, for example, I tried to show this by having the tree idea (the tree inside of the thought bubble) be somewhat similar to the external, mind-independent tree (the tree in front of the spikey-haired dude). But if this is right--if ideas get to represent or be about external things by being similar to them in the right sorts of way--then we run into a problem: we are only justified in thinking that two things are similar if we have experienced them both. If indirect realism is right, however, how do we know that our ideas are similar to external objects? According to this picture, the only access we have to external objects is by our ideas that we have of them. So we have no way to get at the external objects in order to confirm that these things are indeed similar to our ideas of them. It would be like claiming that a certain portrait represents a particular individual, Bob, who no one has actually ever seen. If no one has actually seen Bob, then how do we know that the picture looks like him at all? So the relation between external objects and ideas can't be one of similarity. But what other options are there? None that are coherent, says this line of argument. (2) The veil of perception. Similar to the last objection, this one claims that there is, according to indirect realism, a perpetual veil of perception between us and things in the external world. We can never get at things directly, in other words, so how can we be sure that these things are even there? One answer might be: well, that there are external objects that are similar enough to our ideas is simply the best explanation for why we have the ideas that we do. Remember our explanation of the view: "why do I have the sensation of seeing typed words right now? Because there are typed words in front of me now, and they are causing me to have an idea of typed words. It is through this idea, then, that I have access to the typed words that exist out in the world." In response to this objection, however, is the following: the indirect realist has to at least admit that there are somtimes ideas that are not caused or connected to external objects. Just think of all the things that led the indirect realist to be an indirect realist in the first place--dreams, hallucinations, illusions, etc. Since the existence of external, mind-independent objects doesn't help explain why we have the ideas we do in these sorts of cases, why should we think it's any better of an explanation in other types of cases. Finally, just try to say--fill in the gritty details, that is--how it could be that an external, mind-independent thing causes or affects a mind-dependent idea. It's incoherent! (3) Inconceivability Argument. Try to imagine something without imagining that you are there perceiving it. Go ahead. It's impossible. Everytime you try to imagine something, you have to imagine that you are looking in on the thing you've imagined--perceiving it from above, so to speak. This (supposedly) shows that objects do not exist independent of minds or ideas. [Incidentally, there's a problem with this argument. What is it?] (4) Variability Argument. Recall problem (2) for Direct Realism: "What may look one way to you may look another way to another. Moreover, what may look one way to you at one time, may look another way to you at another. Colors, tastes, smells, feels, etc., can all vary from observer to observer, and can vary in the same observer at different times. If this is right, then which perspective is privledge? And how do we account, on the naive view, for the fact that some people have got it wrong, if there is such a priveledged perspective?" Notice that this isn't just a problem for colors, tastes, smells, etc., but it also seems to be the same with shapes, extension, texture, solidity, motion, etc. What may look smooth far away, may look jagged close-up; what is small far away may be large close-up; what is oblong from one perspective, can be perfectly round from another; what moves fast to one, can move slow to another, etc. In other words, it seems that all properties can vary from observer to observer, or from one time to another in the same observer. But if this is right, and if none of these perspectives is privledged, then what's left for external objects to be? So, to accommodate the above sorts of objects, we might modify our Theory of Perception to the following...
  • So, on this view, things would 'disappear' if there weren't any mind to perceive it. Although this is sort of the wrong way of looking at it, since there are no objects 'out there' to disappear. Moreover, if there is a mind that perceives everything all of the time--perhaps God, say--then things wouldn't 'disappear' in any sense. However, you might wonder whether, like direct realism, idealism can make any sense of the distinction between 'veridical' ideas and 'illusory' ones. Even the idealist has to admit that certain ideas, such as the one of you reading a string of words right now, are more vivid, steady, distinct, and orderly, than other ideas, such as the one you have when you have the idea of a watery image on hot asphalt. Also, some ideas are voluntary (as when you purposely look at the sun and then look away and see an orangey-red after image), while others are involuntary (as when you are reading the flow of these typed words right now). Can there be a distinction, then, on this view between 'dreams' and 'reality', for example?
  • Refering to a person whowho is selectivelylooking at or listening to a certain task and doing effort
  • variations on the Stroop task (lab activity) read colored words vs. name colors of colored words
  • very little about the unattended message is processed: can tell whether it was a human voice or a noise can tell whether the voice was male or female this information is limited cannot tell what language was spoken cannot report any of the words spoken, even if the same word was repeated over and over again what does this tell us? theoretically, difficult to attend to two things at once; can tell us what can draw attention...such as hearing your name in the unattended ear but when your attention gets drawn to the unattended ear, you lose information from tha attended ear ( cocktail party phenomenon .)
  • The conclusion reached and embodied in theories of the 1950s was that somewhere in the system was a bottleneck. Views differed as to where the bottleneck occurred. One of the most influential of the psychological models of selective attention was that put forward by Broadbent in 1958. He postulated that the many signals entering the central nervous system in parallel with one another are held for a very short time in a temporary “buffer.” At this point the signals are analyzed for features such as their location in space, their tonal quality, their size, their colour, or other basic physical properties. They then pass through a selective “filter” that allows only those signals with the appropriate properties to proceed along a single channel for further analysis. Part of the lower-priority information held in the buffer will fail to pass this stage before the time limit on the buffer expires. Items lost in this way have no further effect on behaviour. The original theory held that signals from only one source at a time could proceed. Subsequent work cast doubt on this explanation, and it was later modified by Anne Treisman, to suggest that the filter does not completely block, but simply attenuates, the nonattended signals.
  • With the notion of attenuation, rather than exclusion, of nonattended signals came the idea of the establishment of thresholds . Thus threshold sensitivity might be set quite low for certain priority classes of stimuli, which, even when basically unattended and hence attenuated, may nevertheless be capable of activating the perceptual systems. Examples would be the sensitivity displayed to hearing one’s own name spoken or the mother’s sensitivity to the cry of her child in the night. This latter example demonstrates how processing at some level occurs even in sleep . Before attention can be said to be deployed on the activating event, however, the brain must return to a state of wakefulness. Some theorists have considered that there is no real need to postulate an early filter at all. They suggest that all signals reach central brain structures, which are, according to current circumstances, weighted to take account of particular properties. Some have a high weighting, for example, in response to one’s own name; others are weighted according to the immediate task or interest. Among the concurrently active structures, that with the highest weighting gains awareness and is most directly responded to.
  • Treisman & Geffen (1967) tests between attenuation and late selection -- guess who wins?! dichotic listening + detect target words in either channel (tap upon detection) detection much worse in unattended channel, supporting attenuation...if late selection, detection should be no problem since all info is getting through
  • Sustained attention: vigilance Sustained attention, or vigilance, as it is more often called, refers to the state in which attention must be maintained over time. Often this is to be found in some form of “watchkeeping” activity when an observer, or listener, must continuously monitor a situation in which significant, but usually infrequent and unpredictable, events may occur. An example would be watching a radar screen in order to make the earliest possible detection of a blip that might signify the approach of an aircraft or ship. It is especially difficult to detect infrequent signals of this nature. Vigilance is difficult to sustain. No single theory explains vigilance satisfactorily, probably because of its complexity. In the first place, there is a distinction between sustaining attention in a detection task, where the overall workload is high, and sustaining it when little is happening except for the occasional looked-for events. Under both conditions performance can decline over time. Much depends on the allocation of neural resources to deal with the task. These resources are somewhat limited by the processing capacity already mentioned. When the task is complex, detection difficult, time limited, and a series of decisions required using variable data, the brain may not succeed in coping. Long, boring, and for the most part uneventful tasks result in lowered performance with regard to both speed and accuracy in detecting looked-for events. If the task is interesting or is taking place in a stimulating environment, the individual will be better able to sustain attention and maintain performance. The frequency of task-relevant events holds a significant influence on vigilance performance. Generally speaking, the more frequent the events are, the better the performance, while long periods of inactivity constitute the worst case for performance. Surprisingly, the ratio of signals to nonsignal stimuli makes little difference to performance. The magnitude of the signal, however, is significant. During the course of a watch, expectancies develop about the frequency with which signals appear. If a signal occurs after an atypical interval, it is less likely to be detected. Performance can be improved (up to a point) by increasing task complexity, and in some vigilance situations the introduction of a secondary task can actually improve performance on the primary task. Performance is also enhanced when the individual receives feedback on the vigilance effort. Performance tends to dwindle in a noisy environment, particularly if the noise is high-pitched and loud and the task is difficult. Lack of sleep also impairs performance. Conversely, vigilance can be improved—or at least lapses prevented—by short periods of rest or by conversation or other mild forms of diversion. Monetary or other rewards tend to improve performance, as do some stimulant drugs
  • Transcript

    • 1. Sensation andPerceptionDR Mohamed Youssef Abuzied
    • 2. Sensation & Perception“ The study of perception is concerned with identifyingthe process through which we interpret and organizesensory information to produce our conscious experienceof objects and object relationship.”We are now turning our attention to the topic of“Sensation & Perception,” a specialty area withinPsychology that works at understanding how our senseswork & how we perceive stimuli in the environment. So,with no further delay….
    • 3. Let’s begin with somebasic definitions… S ense – Physical system that receives physical stimulation from surrounding environment and translates that stimulation into an electrochemical message S ensation – The electrochemical message in neurons transmitting information from the sense organ to the brain. P erception – Processing of information done by the brain – mental processes that organize and interpret sensory information that has been transmitted to the brain.
    • 4. Transduction So the brain’s “language” is electrochemical! All senses involve something called receptor cells. Their job is to transduce (transform or even “translate”) physical stimulation/physical energy from the environment into electrochemical messages that can be understood by the brain.
    • 5. The mystery of featuredetectors… Feature detectors are cortical neurons that respond to specific features of a scene (e.g., particular edges, lines, angles and movements) The brain then needs to assemble the whole image from these specific features. “…perceptions arise from the interaction of many neuron systems, each performing a simple task.”
    • 6. Perception“ Perception is the process of receiving information about and making sense of the world around us. It involves deciding which information to notice, how to categorize this information and how to interpret it within the framework of existing knowledge.“ A process by which individuals organize and interpret their sensory impressions in order to give meaning to their environment. 6 Organizational Behavior / Perception
    • 7. Perception Defined The process by which we become aware of objects and events in the external world. The process of making sense of the world around us. Many people ignore the fact that all of us are different and that these differences equip us to view the world from our very own vantage points. Usually we spend more energy defending our own position than understanding others. Where does the triangle begin?
    • 8. The Perceptual Process1. Sensation 3. Organization – An individual’s ability to – The process of placing detect stimuli in the selected perceptual immediate stimuli into a environment. framework for1. Selection “storage.” – The process a person 3. Translation uses to eliminate some – The stage of the of the stimuli that have perceptual process at been sensed and to which stimuli are retain others for further interpreted and given processing. meaning. 8 Organizational Behavior / Perception
    • 9. Factors influencing perception A number of factors operate to shape and sometimes distort perception. These factors can reside in the perceiver, in the object or target being perceived or in the context of the situation in which the perception is made. 9 Organizational Behavior / Perception
    • 10.  Factors influencing Perception Factors in the perceiver • Attitudes • Motives • Interests • Experience • Expectations Factors in the situation • Time Perception • Work Setting • Social Setting Factors in the Target • Motion • Sounds • Size • Background • Proximity 10 • Similarity Organizational Behavior / Perception
    • 11. Perceptual organization It is the process by which we group outside stimuli into recognizable and identifiable patterns and whole objects. Certain factors are considered to be important contributors on assembling, organizing and categorizing information in the human brain. These are- Figure ground- Perceptual grouping11 Organizational Behavior / Perception
    • 12. Perceptual organization Three Principles of Organization: – A) Binary Opposition (all things in pairs)  male/female, short/tall, white/black, good/bad – B) Already formed social categories  101 students, sorority sisters, UK basketball players, Italians – C) We also organize by similarities  size (big buildings), color (things that are purple), space (things from Hawaii), smell (things that make us hungry), function (computer, phone, TV, DVD, VCR, CD player, pager, palm)
    • 13. The Cognitive Approach emphasizesthat people are shaped (& differ. fromeach other) because their perceptions &their thought processes differ. Sounderstanding some backgroundinformation on how we perceive thingsin our environment may help assist us inour understanding of the Cognitiveapproach.
    • 14. Schemas and PerceptualSet A perceptual set is… A mental predisposition to perceive one thing and not another” This is based on experiences, assumptions and expectations.
    • 15. What shapes ourperceptual sets? What things do you think might affect our perceptual sets (i.e., our tendency to perceive things in certain ways)? Context effects Past experiences Effects of our culture
    • 16. Schematas or CognitiveFrameworks To eliminate the chaos of life (entropy) and help make sense of the world, we simplify and reduce our world We put our “selected” data in cognitive “folders” – Also called: Schemata or Cognitive Frameworks
    • 17. Schemas Another word used to describe perceptual set is schemas. Schemas can influence our perception because we tend to see things that we expect to see or wish to. We interpret things based on similar things we have experienced in the past –this is called assimilation.
    • 18. Schemas…..  Now what do you think would happen if we receive new information that doesn’t not fit our schemas?  When we receive new information we can ignore it (!)  or we can change ourSchemas are almost like a schemas to fit the new box that we put information into. information. This is called The way we organize compartmentsin the box is based on things like our past experiences, accommodation.contexts, etc. and this influences our perceptions!
    • 19. Gestalt laws of grouping A major aspect of Gestalt psychology is that it implies that the mind understands external stimuli as whole rather than the sum of their parts. The wholes are structured and organized using grouping laws. These laws deal with the sensory modality vision however there are analogous laws for other sensory modalities . Through the 1930s and 40s Wertheimer, Kohler and Koffka formulated many of the laws of grouping through the study of visual perception.
    • 20. Law of Proximity – The law of proximity states that when an individual perceives an assortment of objects they perceive objects that are close to each other as forming a group. For example, in the figure illustrating , we perceive the collection of circles to be in groups.
    • 21. Law of Similarity – The law of similarity states that elements within an assortment of objects will be perceptually grouped together if they are similar to each other. This similarity can occur in the form of shape, colour, shading or other qualities .
    • 22. Law of Closure – The law of closure states that individuals perceive objects , as being whole when they are not complete. We tend to complete the incomplete Specifically, when parts of a whole picture are missing, our perception fills in the visual gap. The purpose of completing a regular figure is in order to increase the regularity of surrounding stimuli.
    • 23. Law of Symmetry – The law of symmetry states that the mind perceives objects as being symmetrical and forming around a center point. It is perceptually pleasing to be able to divide objects into an even number of symmetrical parts. Therefore, when two symmetrical elements are unconnected the mind perceptually connects them to form a coherent shape.
    • 24. Law of CommonFate – Objects are perceived as lines that move along the smoothest path. We perceive elements of objects to have trends of motion, which indicate the path that the object is on. The law of continuity implies the grouping together of objects that have the same trend of motion and are therefore on the same path.
    • 25. Law of Continuity – The law of continuity states that elements of objects tend to be grouped together, and therefore integrated into perceptual wholes if they are aligned within an object . We are less likely to group elements with sharp abrupt directional changes as being one object.
    • 26.  The sense-datum theory can say, however, that we areindirectly aware of ordinary objects: that is, aware of them by being aware of sense-data.
    • 27. The Naive Theory ofPerception (A.K.A: DirectRealism)
    • 28. The Not-so-Naive Theoryof Perception (AKA:Indirect Realism)
    • 29. The Not-so-Naive butTotally Crazy Theory ofPerception (AKA: Idealism)
    • 30. What is Attention? ability to focus on a task ability to concentrate refers to the allocation of processing resources
    • 31. Attention In daily language it refers to concentrationAttention has two broad dimensions :a- selectivity b- intensity
    • 32. Attention Quality of information processing : Perception ,processing and storing of information wit a good intensity So Attention can be defined as the state of the processing system that is optimally tuned in terms of selectivity and intensity
    • 33. Attentional Behavior Now more dimensions will appear E.g. Divided Vs Sustained attention
    • 34. Different Aspects ofAttention selective attention divided attention automaticity
    • 35. Selective Attention Difficult to attend to more than one thing at the same time Trying to attend to one task over another requires selective attention Selective Attention (Visual) slower to name color when word says a different color than to name the color of an colored square
    • 36. why does this happen? – reading is an automatic process – color naming is a controlled process – automatic process of reading interferes with our ability to selectively attend to ink color
    • 37. Selective Attention(Auditory) Dichotic listening In a typical dichotic listening task, Ss hear two messages simultaneously...one message in one ear and one message in the other; As they are listening, they are asked to shadow one of the messages (i.e. repeat back the words from one message only
    • 38. Theoretical Interpretationsof Selective Attention Bottleneck theories or filter theories bottleneck is a mechanism that limits the amount of information to be attended to what gets through? what is selected and when?
    • 39. Early selection Broadbent (1958) proposed that physical characteristics of messages are used to select one message for further processing and all others are lost .He postulated that the many signals entering the central nervous system in parallel are held for a very short time in a temporary “buffer.”
    • 40. Attenuation Treisman (1964) proposed that physical characteristics are used to select one message for full processing and other messages are given partial processing
    • 41. Late selection Deutsch & Deutsch (1963) proposed that all messages get through, but that only one response can be made (late selection)
    • 42. Divided Attention andDual Task Performance trying to attend to two stimuli at once and making multiple responses rather than making one response to multiple stimuli (interference)
    • 43. Sustained attention:vigilance Sustained attention, or vigilance, as it is more often called, refers to the state in which attention must be maintained over time.
    • 44. Two-process” theories ofattention. Controlled search and automatic detection. Controlled search is easily established and is largely under the individual’s control in that it can be readily altered or even reversed. It is strongly dependent on the stimulus load. It has been suggested that it uses short-term memory.
    • 45. Automatic Detection . By contrast, automatic detection, or automatic processing, operates in long-term memory and is dependent upon extensive learning. It comes into operation without active control or attention by the individual, it is difficult to alter or suppress.
    • 46. Broadly speaking, the two types ofattention can be characterized asfocal and automatic .  Someone who is focally attentive is highly aware, consciously in control, and selective in handling sensory phenomena. A person in such a state also uses the brain for short-term storage. Focal attention makes great demands on brain capacity
    • 47.  Automatic attention makes fewer demands but is relatively inflexible, as it cannot cope with the unexpected.
    • 48.  The focal and automatic modes may be illustrated by a driving example: a new driver has to attend to gear shifting in a focal way (actively thinking about it), while an experienced driver changes gears automatically (not needing to think about it).

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