Stimuli are events in the environment that influence behavior. A single stimulus can serve many different functions. Listed below are several functions that a stimulus can serve. Show Discriminative Stimulus A discriminative stimulus influences the occurrence of an operant response because of the contingencies of schedules of reinforcement or paradigms of reinforcement/punishment that are or have been associated with that response. Many authors further suggest that discriminative stimuli provide information to the organism, allowing it to respond appropriately in the presence of different stimuli. An observing response is sometimes necessary for presentation of the discriminative stimulus/stimuli. For example, different individuals can serve as discriminative stimuli in a joke-telling situation. The jokes that you tell your priest are probably different from the jokes that you tell your best friend because of your past history of telling jokes to both people. Experimentally, we can observe the discrimination of stimuli by associating different discriminative stimuli with different schedules of reinforcement or paradigms of reinforcement/punishment. For instance, in the laboratory, a pigeon could be required in the presence of a steady chamber light to peck a key on a Fixed Interval schedule to produce food, whereas it could be required in the presence of a blinking chamber light to pull a chain on a Variable Ratio schedule to turn off a loud noise. The discriminative stimuli clarify the "rules of the game," making each prevailing three-term contingency unambiguous. Quotations Eliciting Stimulus An eliciting stimulus is a change in the environment that is highly correlated with the occurrence of a later response. An eliciting stimulus is an essential component of Pavlovian conditioning. For example, if a piece of chocolate (unconditioned stimulus) is placed into your mouth, then you will probably salivate copiously (unconditioned response). Placing the piece of chocolate into the mouth is said to elicit salivation. Quotations Emotional Stimulus Some stimuli may produce an emotional reaction which may influence the occurrence of behavior. For example, a game of backgammon might be interrupted by news of the unexpected death of a famous politician. Quotations Reinforcing Stimulus A reinforcing stimulus is one that increases the occurrence of behaviors that it follows. For instance, the receipt of a trophy may increase the chances of a young girl competing in a yearly road race. Nominal Stimulus A discriminative stimulus may have many identifiable attributes. Although we can readily observe the organism's response to the whole stimulus, it may not be clear exactly which attributes of the stimulus are controlling the behavior (see functional stimulus). The unanalyzed stimulus as a whole is said to be the nominal stimulus. For example, your friend asks you to look at a passing sports car. It is not clear just what your friend wanted you to note about the car: its color, make, speed, location, driver, etc. Functional Stimulus The functional stimulus refers to the specific attributes of the discriminative stimulus that exert control over the organism's behavior. In the above example, your friend may have been particularly interested in the car's color. Stimulus Control We speak of stimulus control when a discriminative stimulus changes the likelihood of an operant response. The controlling relation between the discriminative stimulus and the operant response (what Skinner called attention) comes about because of the reinforcer/punisher that has followed the operant response in the presence of that discriminative stimulus. Thus, the three-term contingency lies at the root of stimulus control. Glossary Index | Quotations In behavioral psychology (or applied behavior analysis), stimulus control is a phenomenon in operant conditioning (also called contingency management) that occurs when an organism behaves in one way in the presence of a given stimulus and another way in its absence. A stimulus that modifies behavior in this manner is either a discriminative stimulus (Sd) or stimulus delta (S-delta). Stimulus-based control of behavior occurs when the presence or absence of an Sd or S-delta controls the performance of a particular behavior. For example, the presence of a stop sign (S-delta) at a traffic intersection alerts the driver to stop driving and increases the probability that "braking" behavior will occur. Such behavior is said to be emitted because it does not force the behavior to occur since stimulus control is a direct result of historical reinforcement contingencies, as opposed to reflexive behavior that is said to be elicited through respondent conditioning. Some theorists believe that all behavior is under some form of stimulus control.[1] For example, in the analysis of B. F. Skinner,[2] verbal behavior is a complicated assortment of behaviors with a variety of controlling stimuli.[3] CharacteristicsThe controlling effects of stimuli are seen in quite diverse situations and in many aspects of behavior. For example, a stimulus presented at one time may control responses emitted immediately or at a later time; two stimuli may control the same behavior; a single stimulus may trigger behavior A at one time and behavior B at another; a stimulus may control behavior only in the presence of another stimulus, and so on. These sorts of control are brought about by a variety of methods and they can explain many aspects of behavioral processes.[4] In simple, practical situations, for example if one were training a dog using operant conditioning, optimal stimulus control might be described as follows:
Establishing stimulus control through operant conditioningDiscrimination trainingOperant stimulus control is typically established by discrimination training. For example, to make a light control a pigeon's pecks on a button, reinforcement only occurs following a peck to the button. Over a series of trials the pecking response becomes more probable in the presence of the light and less probable in its absence, and the light is said to become a discriminative stimulus or SD.[6] Virtually any stimulus that the animal can perceive may become a discriminative stimulus, and many different schedules of reinforcement may be used to establish stimulus control. For example, a green light might be associated with a VR 10 schedule and a red light associated with a FI 20-sec schedule, in which case the green light will control a higher rate of response than the red light. GeneralizationAfter a discriminative stimulus is established, similar stimuli are found to evoke the controlled response. This is called stimulus generalization. As the stimulus becomes less and less similar to the original discriminative stimulus, response strength declines; measurements of the response thus describe a generalization gradient. An experiment by Hanson (1959)[7] provides an early, influential example of the many experiments that have explored the generalization phenomenon. First a group of pigeons was reinforced for pecking a disc illuminated by a light of 550 nm wavelength, and never reinforced otherwise. Reinforcement was then stopped, and a series of different wavelength lights was presented one at a time. The results showed a generalization gradient: the more the wavelength differed from the trained stimulus, the fewer responses were produced.[7] Many factors modulate the generalization process. One is illustrated by the remainder of Hanson's study, which examined the effects of discrimination training on the shape of the generalization gradient. Birds were reinforced for pecking at a 550 nm light, which looks yellowish-green to human observers. The birds were not reinforced when they saw a wavelength more toward the red end of the spectrum. Each of four groups saw a single unreinforced wavelength, either 555, 560, 570, or 590 nm, in addition to the reinforced 550 wavelength. The birds were then tested as before, with a range of unreinforced wavelengths. This procedure yielded sharper generalization gradients than did the simple generalization procedure used in the first procedure. In addition, however, Hansen's experiment showed a new phenomenon, called the "peak shift". That is, the peak of the test gradients shifted away from the SD, such that the birds responded more often to a wavelength they had never seen before than to the reinforced SD. An earlier theory involving inhibitory and excitatory gradients partially explained the results,[8] A more detailed quantitative model of the effect was proposed by Blough (1975).[9] Other theories have been proposed, including the idea that the peak shift is an example of relational control; that is, the discrimination was perceived as a choice between the "greener" of two stimuli, and when a still greener stimulus was offered the pigeons responded even more rapidly to that than to the originally reinforced stimulus.[10] Matching to sampleIn a typical matching-to-sample task, a stimulus is presented in one location (the "sample"), and the subject chooses a stimulus in another location that matches the sample in some way (e.g., shape or color).[11] In the related "oddity" matching procedure, the subject responds to a comparison stimulus that does not match the sample. These are called "conditional" discrimination tasks because which stimulus is responded to depends or is "conditional" on the sample stimulus. The matching-to-sample procedure has been used to study a very wide range of problems. Of particular note is the "delayed matching to sample" variation, which has often been used to study short-term memory in animals. In this variation, the subject is exposed to the sample stimulus, and then the sample is removed and a time interval, the "delay", elapses before the choice stimuli appear. To make a correct choice the subject has to retain information about the sample across the delay. The length of the delay, the nature of the stimuli, events during the delay, and many other factors have been found to influence performance on this task.[12] CannabinoidsPsychoactive cannabinoids from the Cannabis plant (phytocannabinoids), from the body (endocannabinoids), and from the research lab (synthetic cannabinoids) produce their discriminative stimulus effects by stimulation of CB1 receptors in the brain.[13] See also
References
Further reading
|
When stimulus is similar to another stimulus then it is called?
Pos Terkait
Copyright © 2024 ketajaman Inc.
