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Chapter 8

Learning and Behaviour-Chapter 8

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Anneke Olthof

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1 Learning and Behaviour-Chapter 8 Stimulus Control of Behaviour -both Thorndike and Skinner recognized that instrumental responses and reinforcers occur in the presence of a particular stimuli; these stimuli can come to determine whether or not the instrumental response is performed -stimulus control of instrumental behaviour is evident is many aspects of life studying is under strong control of school related stimuli, students who fall behind in their work may be motivated to make resolutions to study a lot when they go home for the holidays, however intentions like these are rarely carried out because the stimuli of the holidays are very different from the stimuli students experience when class is in session -the stimulus control of behaviour is an important aspect of how organisms adjust to their environment Identification and Measurement of Stimulus Control -to investigate stimulus control of behaviour, we first have to know how to identify and measure it Differential Responding and stimulus Discrimination -looking at the experiment with the two pigeons pecking at the red circle with the white triangle in the middle when we split the two stimulus up, we find that one bird responds with more pecking to just the white triangle and the other bird responds to more pecking to just the red circle; DIFFERENTIAL RESPONDING IS OCCURING -experiment first shows how to experimentally determine whether instrumental behaviour has come under the control of a particular stimulus; the stimulus control of instrumental behaviour is demonstrated by variations in responding (differential responding) related to variations in stimuli **if an organism responds one way in the presence of one stimulus and a different way in the presence of another stimulus, its behaviour has come under control of those stimuli -stimulus discrimination: differential responding in the presence of two or more stimuli -if an organism does not discriminate between two stimuli, its behaviour is not under the control of those cues -in the absence of special procedures, one cannot always predict which of the various stimuli an organism experiences will gain control over its instrumental behaviour Stimulus Generalization -stimulus generalization: responding to test stimuli that are different from the cues that were presented during training -stimuli may be defined in all kinds of ways and sometimes widely different objects are considered instances of the same stimulus because they share the same functionsuch as a wheel, it may be large or small, have spokes or not, different colours or different textures -some stimuli might even have to be a particular shade in general, or a particular wave length in sound -numerous factors are involved in the identification and differentiation of stimuli -organism is said to show stimulus generalization if it responds in a similar fashion to two or more stimuli -phenomenon of stimulus generalization was first observed by Pavlov as he found that after one stimulus was used as a CS, his dogs would also make the conditioned response to other similar stimuli -stimulus generalization gradient: a gradient of responding that is observed if participants are tested with stimuli that increasingly differ from the stimulus that was present during trainingex. pigeons were tested with many different colours but were only reinforced with a yellowish-orange light (580- 2 nm), but we found that they would also respond to lights in similar colours such as lights with wavelengths of 570-nm and 590-nm Stimulus Generalization Gradients as Measures of Stimulus Control -stimulus generalization gradients are an excellent way to measure stimulus control because they provide precise information about how sensitive the organisms behaviour is to variations in a particular aspect of the environmentable to figure out how much a stimulus has to be changed in order to produce a behaviour -in the previous example with the pigeons and the lights, if they had not responded on the basis of colour of the key lights, similar high rates would have occurred as different colours were projected on the key—the stimulus generalization gradient would have been flat -a steep generalization gradient indicates good control of behaviour by the stimulus dimension that is tested, a flat generalization gradient indicates poor stimulus control **What determines the degree of stimulus control that is obtained? Stimulus and Response Factors in Stimulus Control -need to realize that all stimulus situations can be analyzed in terms of multiple features, such as when the pigeons analyzed the stimuli in terms of the white triangle or the red background; even if the stimuli were just red you would be able to analyze it in terms of brightness, shape or location in the experimental chamber -central issue in the analysis of stimulus control is what determines which of the numerous features on a stimulus situation gains control over the instrumental behaviour -such as the example of a football game, we cheer because of many things that are going on such as the announcer announcing something good, scoring and others cheering around us -lab studies are conducted with stimuli that consist of more easily identified features Sensory Capacity and Orientation -most obvious variable that determines whether a particular stimulus feature comes to control responding is the organism’s sensory capacity and orientations which sensory information is included in the organism’s sensory world -limitations on the stimuli that can come to control behaviour are also set by whether the individual comes into contact with the stimuli—ex. parents handing mobile above the child’s crib, but at the angle that the child is laying at, they are unable to see what animals are on the mobile -studies of stimulus control are often used to determine what an organism is, or is not able to perceive; such as answering the question “can horses see colour,” this question was answered by setting up an experiment where they were able to pick between a colour shown and gray and when they picked the colour they would be rewarded with foodfound that horses do have good colour vision -studies of stimulus control have also been used to determine the visual and hearing thresholds of several species of pinniped (seals and sea lions) Relative Ease of Conditioning Various Stimuli -having necessary sense organs and the appropriate sensory orientation does not guarantee that the organism’s behaviour will come under the control of a particular stimulus -whether a stimulus comes to control a behaviour, also depends on the presence of other cues in the situation 3 -overshadowing: interference with the conditioning of a stimulus because of the simultaneous presence of another stimulus that is easier to condition such as trying to teach a child to read by following along, but there are big pictures to distract them, child will memorize story by picture and not the words -Pavlov was the first to observe that if two stimuli are presented at the same time, the presence of the more easily trained stimuli may hinder learning about the other one; in his experiment it usually dealt two stimuli that differed in intensity, the more intense stimuli would be learned and rapidly overshadowed the weaker stimuli Type of Reinforcement -development of stimulus control also depends on the type of reinforcement that is used, as certain types of stimuli are more likely to gain control over the instrumental behaviour in appetitive than in aversive situations -did the experiment with pigeons using a light/tone where they would have to press the lever when it came on in order to avoid an aversive situation in one condition or receive food in another condition; the experimenters wanted to see which of the stimuli the birds were responding to in each situation -in the aversive shock situation they found that the pigeons responded to the tone much more than the light when the stimuli were split up, and in the food situation the pigeon’s responded much more to the red light than to the tone when shown aloneshows that stimulus control of instrumental behaviour is determined in part by the type of reinforcement that is used -found that visual control predominates when the CS acquires positive or appetitive properties, and auditory control predominates when the CS acquires negative properties -in the real world, a visual cue for food is more common and an auditory cue for predators or to signal danger is also more common Types of Instrumental Response -another factor that can determine which of the several features of a compound gains control over behaviour is the nature of the response required for reinforcement -did the study with the dogs where the metronome and the buzzer were placed in front or behind the dogs, there were two groups; one group of dogs raised right/left paw when the buzzer or metronome sounded, and the other group raised a paw when the buzzer sounded but not when the metronome was sounded making is a go, no-go situation -results indicated that responses that are differentiated by location (right/left) are more likely to come under control of the spatial feature of auditory cues (this is because the dog still raised its right paw first even if the buzzer and metronome were switched from front to back) and responses that are differentiated by quality (go, no-go) are more likely to come under the control of auditory cues -this is known as the quality-location effect Stimulus Elements vs. Configural Cues in Compound Stimuli -stimulus element approach: an approach to the analysis of control by compound stimuli which assumes that participants respond to compound stimulus in terms of the stimulus elements that make up the compoundsuch as the assumption that a particular stimulus feature (sound quality) was perceived the same way regardless of the status of other feature (sound location) -configural cue approach: an approach to the analysis of stimulus control which assumes that organisms respond to compound stimulus as an integral whole rather than a collection of separate and independent stimulus elements individuals respond to a compound stimulus in terms of its unique configuration of its elements; in this approach the stimulus elements are important because of the way that they contribute to the entire configuration of stimulation provided by the compound 4 -example of configural cue= the sound of an orchestra originates from the sound of individual instruments, but the sound of the orchestra is very different from the sound of any individual instruments—we primarily hear the configuration of sounds made by the individual instruments -according to the configural cue approach, overshadowing reflects different degrees of generalization decrement from training to testing for the overshadowing and the control groups Learning Factors in Stimulus Control -stimulus and response factors are the starting point for stimulus control, however the fact that certain stimuli can be perceived does not ensure that those stimuli will come to control behaviour -ex. novice chess player might be able to see two different patterns on a chess board without being able to identify which represents the more favourable configuration -whether or not certain stimuli come to control behaviour often depends on what the organism has learned about those stimuli, not just whether the stimuli can be detected—this thought originated in efforts to explain the phenomenon of stimulus generalization which is when learning about a CS becomes transferred to other stimuli on the basis of physical similarity of those test stimuli to the original CS -however Lashley and Wade rejected the idea that stimulus generalization reflects the transfer of learning, they stated that stimulus generalization reflects the absence of learning and proposed that it occurs if an organism has not learned to distinguish differences among stimuli they consider the shape of a stimulus generalization gradient to be determined primarily by the organism’s previous learning experiences rather than by the physical properties of the stimuli tested Stimulus Discrimination Training -we find that Lashley and Wade were closer to the truth than Pavlov as numerous studies have shown that stimulus control can be dramatically altered by learning experiences -most powerful procedure for bringing behaviour under the control of a stimulus is stimulus discrimination training -stimulus discrimination training: stimulus discrimination training can be conducted using either classical conditioning or instrumental conditioning procedures  Classical Conditioning: classical procedure in which one stimulus (CS+) is paired with the US on some trials and another stimulus (CS-) is presented without the US on other trials—as a result of this procedure the CS+ comes to elicit a conditioned response and the CS- comes to inhibit this response -did the experiment where the tone 2000 cycles/second(A+) is paired with the US and is reinforced and the tone 8000 cycles/second (B- that by the 15th session, the subjects respond to the A+ tone more than 85% of the time, responding to the B- also increased at first, but not rapidly and by the 10th session it had gradually declined; by the end of the experiment, participants showed a very nice differential responding to the two tones -found that the conditioned responding that develops to A+ generalized to B- at first, but with further training responding to B- declines and a clear discrimination becomes evident **confuse the two at first, but learnt to tell them apart with training  Instrumental Conditioning: procedure in which reinforcement for responding is available whenever one stimulus (the S+ or S ) is present and not available whenever another stimulus (S- delta) , or S is present -example of this would be when children are taught what to do at an intersection controlled by a traffic light; stimulus (green light ) that signals the availability of reinforcement for the instrumental response is D known as the S+ or S and the stimdelta(the red light) that signals the lack of reinforcement for responding is called the S- or S  initially the child might try to cross the street for both the S+ 5 (green light) and the S- (red light) but as training progresses, responding in the presence of S+ persists and responding of S- declines -stimulus discrimination procedure established control by the stimuli that signal when reinforcement is not availableone S+ and S- have gained control over the organism’s behaviour, they are called discriminative stimuli -discriminative stimuli: a stimulus that controls the performance of instrumental behaviour because it signals the availability or non-availability of reinforcement -discrimination training can also be conducted with S+ and S- stimulus presented at the same time next to each other, in a situation where the subject can respond to one or the other—allows direct comparison -multiple schedule of reinforcement: an instrumental conditioning procedure in which responding is reinforced in the presence of one stimulus (the S+) and not reinforced in the presence of another cue (the S-)  in this case different schedules of reinforcement are in effect during different stimuli and with efficient exposure to such a procedure the pattern of responding during each stimulus will correspond to the schedule of reinforcement in effect during that stimulus -stimulus discrimination and multiple schedules are common outside the lab as nearly all reinforcement schedules that exist outside of the lab are in effect only in the presence of a particular stimuli—ex. playing a game yields reinforcement only when you are in the presence of challenging partners, or driving rapidly is reinforced on the freeway but not when you are on a crowded city street Effects of Discrimination Training on Stimulus Control -discrimination training brings the instrumental response under the control of the S+ and S- -ex. did an experiment with pigeons and tone where there were 3 groups : 1 group (S+= 1000-cps tone where they were rendforced when they would peck a key when this was going off, the S-=no tone, no reinforcement) 2 group (S+= 1000-cps tone where they were reinforced when this tone was one, and S-= 950-cps, no reinforcement) 3 group (no discrimination training) after completion of training procedures, each group was tested for pecking in the presence of tones of various frequencies -control group that did not receive training responded equally in the presence of all test stimuli, the steepest generalization gradien
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