The Visual Capacity of Organisms - Report Example

Perceptual learning Your name Institution Perceptual learning Abstract Visual capacity of organisms makes it possible to recognize intricate body movements, which is important for social communication. This visual capacity uses specialized means to analyze and study various biological movements. This is made possible when organisms learn to discriminate things that are similar. Discrimination is the process where an animal responds to specific stimuli when two or more stimuli are given to an animal continuously. Discrimination usually occurs after training. Thus, an animal or human being can be taught how to discriminate different stimuli. For instance, if a dog is shown a green circle every time it is given food, then it will salivate when it sees the green circle alone. However, the dog may generalize and react to circles of any colors. Perceptual learning refers to improvements in our ability to discriminate between stimuli that are initially highly confusable. Very similar stimuli become easier to discriminate as they become more familiar. This simple fact greatly influences our day-to-day lives. For instance, people quickly detect the face of a friend amongst a crowd of strangers, we notice subtle changes in our favorite foods, and over time, people begin to distinguish varieties of wine that at first seemed identical. In other words, learning results in changes in the way we perceive the world around us. Introduction Some cases of perceptual learning may result from instruction or continuous feedback. Most forms of professional perceptual expertise – wine tasting, radiology, and medical decision-making – involve a considerable amount of deliberate and very explicit training. However, even in the absence of any feedback or instruction, mere exposure to very a similar stimulus improves our ability to tell them apart at a later time. Thus, perceptual learning can result from incidental exposure to the stimuli themselves. Numerous mechanisms for such incidental perceptual learning have been proposed. One of these is the reduction in salience of the features that the two stimuli share in common. The common features (or elements) of the stimuli are shown twice as often as the unique features. Just as familiarity with a stimulus seems to reduce the salience of that stimulus (e.g. latent inhibition and habituation), greater familiarity of particular features such as the common elements might reduce their salience relative to others. This will make the unique features relatively salient in comparison, helping them to stand out or be learned about faster. Another mechanism that has been suggested is mutual inhibition between distinctive features. The unique features of each stimulus are mutually exclusive: they only appear when the distinctive features of the other stimulus are not present. However, the unique features of both stimuli are associated with the common features with which they always coincide. Therefore, the presence of the common features establishes an expectation of the unique features through excitatory associative links. When a particular unique feature is not shown, this expectation is violated, leading to inhibitory learning as predicted by theories like the Rescorla-Wagner model. The unique features of each stimulus then gradually begin to inhibit the unique features of the other stimulus because one always coincides with the surprising omission of the other. Note that this second mechanism is only predicted to occur when the stimuli are intermixed in a way that can sustain gradual inhibitory learning. Responses instructed to take place in the presence of certain stimuli tend to be done in the presence of similar stimuli, which define the real state of stimuli generalization. Stimuli generalization involves judgment, perception, and learning processes. Generalization was as a result of spread of the stimuli in the body, therefore, it depicted the state of animals’ nervous system. As a result, there is an association formed between range of stimuli and the conditioned responses. If the association formed is strong with that of instructed stimuli, then generalization is high. These generalizations occur because an organism cannot differentiate between trained stimuli and test values. According to Gibson 1969, perceptual learning is a process that includes perceptual efficiency of the characteristics that distinguishes between stimuli that are similar, a process that is caused when an organism is exposed to a stimuli and it compares it to other similar stimuli. Theory of generalization ignores the idea of relational properties and test stimuli as necessarily incomplete. This kind of effect can occur if judgment of stimuli is different depending on other stimuli that an organism has once experienced. Experimental studies done on perceptual learning using organisms have made use of versions of certain experimental design. For instance, when animals are exposed to stimuli without any training, they respond differently. Animals have to make distinction of two similar stimuli such as AZ and BZ. In such a condition, A and B are different features of the stimuli, and Z being those features similar that A and B hold in common. An animal in one condition is exposed to the stimuli and is presented on alternate trials, while in another situation; the condition is presented on equal number of times but in separate trials. Discrimination is then analyzed by studying the extent to which generalization occurred when stimuli were presented to animals. It is discovered that generalization is less after intermixed exposure than after fused or blocked exposure. This kind of experiment is used to show an example of perceptual learning effect in which some conditions of preexposure distributed by the intermixed arrangement enhance how serious an organism discriminates a stimuli. Discrimination and generalization usually take place in every day activity. Complete discrimination tends to occur when there is conditioned response to a reinforced or conditioned stimuli; there is no conditioned response as a result of response to other conditioned stimuli elicited by others. Generalization occurs as a result of conditioned response to a reinforced conditioned stimuli transferred completely to other conditioned stimuli. For instance, generalization can occur if a person tastes two similar products that have common features like coca cola and Pepsi. Discrimination entails a situation where an organism learns to distinguish features of similar stimuli and it is aided by exposure in which an organism can compare the stimuli to other. It is worth noting that the effect of preexposure on generalization in associative manner is high with no appeal to changes in the effective salience of stimuli. In any case, if AZ and BZ are preexposed, then there will be formation of associations between several elements of the compound stimuli. In both the blocked and intermixed conditions, excitory inhibition within compound associations A and Z and between B and Z can be expected to form. The intermixed schedule should give room for the formation of inhibitory associations between specific features of the stimuli that are preexposed. For instance, if orange juice is taken at the same time with beer, there will be weak generalization between orange juices to beer because they share few elements. On the other hand, if coke and Pepsi are taken at the same time, there will be strong generalization because these drinks share many elements. Therefore, animals learn to discriminate between similar stimuli by comparing them. For instance, if taking coke causes illness and Pepsi does not, then specific coke will definitely develop strong association with illness while Pepsi will have inhibitory association with no illness. Experiments Experiments conducted by Dwyer, Hodder and Honey on comparisons of the blocked and intermixed schedules using the same different activity gave mixed results. For instance, participants were exposed to two compounds of different tastes. It was noticed that, although generalization of conditioned stimuli was weak after intermixed preexposure than of blocked preexposure there, was no great difference between the two conditions in their influence on the two different judgments. Method of experiment In this experiment, the researchers used participants who were students from university of New South Wales. The stimuli were different checkerboard, which had common elements the Z element, which was shown at the bottom of the figures. Some unique features were added on the checkerboards by altering six adjacent gray squares to one of the brighter colors. However, in similar experiment conducted by Mitchell and Lavis, the stimuli used were not the same in that they were all brightly colored. The unique features that were added differed from one another in shape, color, and location within the checkerboard. The stimuli were presented on a computer monitor where a revolutionary studio was used to control the stimulus presentation on the computer PC. All the participants were preexposed to the stimuli. Half of the participant, the intermixed group, AZ stimulus was presented as an alternative for the presentations of BZ. On the other hand, the blocked group, AZ presentations were given first and then followed by BZ presentations. All the participants were preexposed to the stimulus where they were expected to make their bar presses. On the other hand, the second experiment where participants were given with new instructions presented on a computer screen. They were instructed that they press number X if the stimulus seemed to be the same and D if the stimulus appeared to be different. These experiments provide clear justification of blocked and intermixed effect on the same-different test using simple experiment conducted in experiment one and more intricate experiment conducted within subjects in second experiment. There were two types of test trial in the second experiment: (a) different, in which AZ and BZ were presented, and (b) same, in which AZ and AZ (or BZ and BZ) were presented. The order of stimulus presentation on different trials was balanced across trials. There were 90 test trials in total, divided into two blocks of 45 trials. Within each block, there were 23 trials of each type. After each block, participants were free to rest their eyes if they wished. To analyze the data, we conducted an analysis of variance with a set of planned contrasts. Results of the experiment It is evident that accuracy in responding “same” when identical stimuli were presented was very high, both for stimuli preexposed in the intermixed fashion and for blocked stimuli. Accuracy in responding “different,” however, was much greater for the intermixed stimuli than for the blocked stimuli. Statistical analysis conducted on the data summarized in Figure 3 confirmed these impressions. An analysis of the effect of training order (intermixed followed by blocked, or vice versa) was first conducted on the results of the same–different. Discussion These data provide clear evidence of an intermixed/blocked effect on a same–different test using a simple, between-subjects design in the first experiment and a more complex within-subject design in the second experiment. The results are consistent with Gibson’s (1969) idea that only intermixed preexposure allows comparison of the cues and extraction of the unique features. They do not coincide straightly from the associative inhibitory mechanism put forward by McLaren and Mackintosh in 2000. According to Dwyer et al. 2004, they suggested that the formation of inhibitory associations between A and B in the intermixed condition might actually inhibit performance on the same–different task. They argued that, when AZ and then BZ are presented on the same– different task, the memory of AZ must be retrieved when BX is being viewed if the subject is to give the correct response of “different.” Only in such circumstances, can AZ and BZ be compared with each other and judged different. Dwyer et al. went on to argue insurmountable, and the simple demonstration of an effect in this situation is not enough to disconfirm the theory. The experiments that follow continue to explore the intermixed/blocked effect using the same–different test, but introduce modifications, both in the training and the test procedures, intended to generate more theoretically decisive results. Conclusion This experiments reveals how human and animals learn to discriminate between similar stimuli when studied from the arena of perceptual learning of both humans and animals. This conclusion is retrieved from inhibitory studies of generalization tests. For instance, if AZ is usually paired with biological outcomes and generalization paired to BZ of the resulting conditioned response tested. The strength of generalization is determined by looking at how BZ responds. BZ response will be strong if AZ and BZ are perceptually indistinguishable. The same source of generalization is used to determine response to the same-different task in a certain condition or situation. In addition, if AZ and BZ are distinguishable, then generalization may be determined by some different factors like associative link between BZ and AZ, which are the compound cues. Perceptual learning is also determined by measuring modulations of salience. This idea is based on the reverse habituation mechanism. If a stimulus is presented in absence of motivation, the response evoked which decreases in strength therefore paving way for habituation to occur. Habituation is a result of lack of reinforcement, which leads to effective salience of the stimulus. Stimuli that are familiar are less salient as compared to novel stimuli. Salience can be restored and habituation reversed if activation of stimuli representation by presentation of the same stimuli. This kind of response has been witnessed in humans and rats when responding to certain conditions that present similar stimuli. It is rational to state that what makes it possible to distinguish between intermixed and blocked presentations is the extent to which an organism or participants are in position to note and realize the distinctive characters of the stimuli. This is in line with standard learning theory, which focuses on unique features of compound cues that are less salient. According to this theory, familiar stimuli are said to be less salient than novel stimuli for which no representation exist. References Bugelski, B. R. (1971). Instrumental Conditioning and Learning. New York: General Learning Press. Demany, L. (1985). Perceptual learning in frequency discrimination. Journal of the Acoustical Society of America, 78, 1118-1120. Fahle, M., & Poggio, T. (2002). Perceptual learning. Cambridge, MA: MIT Press. Fiorentini, A., & Berardi, N. (1980). Perceptual learning specific for Orientation and Spatial Frequency. Nature, 287, 43-44. Gibson, E. J. (1969). Perceptual learning and development. New York: Appleton-Century- Crofts. Hall, G & et al (2006). Associative Activation of stimulus representations restores lost salience: Implication for perceptual learning. New York: McGraw Hill. Hall, G. (1991). Perceptual and associative learning. Oxford: Oxford University Press. Hall, G. (2003). Learned changes in the sensitivity of stimulus representations: Associative and non-associative mechanisms. Quarterly Journal of Experimental Psychology, 56B, 43-55. Helson, H. (1964). Adaptation- Level theory. New York: Harper and Row. McLaren, I. P., & Mackintosh, N.J. (2000). An Elemental model of associative Learning: Latent inhibition and perceptual learning. Animal Learning and Behavior, 28, 211-246. Menzel, R .(1997). Learning and memory: A comprehensive reference.Vol.1: Learning theory and behavior (pp. 103-121). Amsterdam: Elsevier. Mundy, M. E., Honey, R. C., & Dwyer, D. M. (2007). Simultaneous presentation of similar stimuli produces perceptual learning in human picture processing. Journal of Experimental Psychology: Animal Behavior Processes, 33, 124–138. NJ: Erlbaum. O’Brien, R. G., & Kaiser, M. K. (1985). MANOVA method for analyzing repeated- measures designs: An extensive primer. Psychological Bulletin, 97, 316–333. Pinerio, O. (2010). The thinking Rat: The new Science of Animal Learning. Virginia: CreateSpace Press. Rodriguez, G., & Alonso, G. (2004). Perceptual learning in flavor-aversion learning: Alternating and blocked exposure to a compound of flavors and to an element of that compound. Learning and Motivation, 35,208–220. Symonds, M., & Hall, G. (1995). Perceptual learning in flavor aversion learning: Roles of stimulus comparison and latent inhibition of common stimulus elements. Learning and Motivation, 26, 203–219. Wagner, A. R. (1981). SOP: A model of automatic memory processing in animal behavior. In N. E. Spear & R. R. Miller (Eds.), Information processing in animals: Conditioned inhibition (pp. 223–266). New York: Hillsdale. Read More

This will make the unique features relatively salient in comparison, helping them to stand out or be learned about faster. Another mechanism that has been suggested is mutual inhibition between distinctive features. The unique features of each stimulus are mutually exclusive: they only appear when the distinctive features of the other stimulus are not present. However, the unique features of both stimuli are associated with the common features with which they always coincide. Therefore, the presence of the common features establishes an expectation of the unique features through excitatory associative links.

When a particular unique feature is not shown, this expectation is violated, leading to inhibitory learning as predicted by theories like the Rescorla-Wagner model. The unique features of each stimulus then gradually begin to inhibit the unique features of the other stimulus because one always coincides with the surprising omission of the other. Note that this second mechanism is only predicted to occur when the stimuli are intermixed in a way that can sustain gradual inhibitory learning. Responses instructed to take place in the presence of certain stimuli tend to be done in the presence of similar stimuli, which define the real state of stimuli generalization.

Stimuli generalization involves judgment, perception, and learning processes. Generalization was as a result of spread of the stimuli in the body, therefore, it depicted the state of animals’ nervous system. As a result, there is an association formed between range of stimuli and the conditioned responses. If the association formed is strong with that of instructed stimuli, then generalization is high. These generalizations occur because an organism cannot differentiate between trained stimuli and test values.

According to Gibson 1969, perceptual learning is a process that includes perceptual efficiency of the characteristics that distinguishes between stimuli that are similar, a process that is caused when an organism is exposed to a stimuli and it compares it to other similar stimuli. Theory of generalization ignores the idea of relational properties and test stimuli as necessarily incomplete. This kind of effect can occur if judgment of stimuli is different depending on other stimuli that an organism has once experienced.

Experimental studies done on perceptual learning using organisms have made use of versions of certain experimental design. For instance, when animals are exposed to stimuli without any training, they respond differently. Animals have to make distinction of two similar stimuli such as AZ and BZ. In such a condition, A and B are different features of the stimuli, and Z being those features similar that A and B hold in common. An animal in one condition is exposed to the stimuli and is presented on alternate trials, while in another situation; the condition is presented on equal number of times but in separate trials.

Discrimination is then analyzed by studying the extent to which generalization occurred when stimuli were presented to animals. It is discovered that generalization is less after intermixed exposure than after fused or blocked exposure. This kind of experiment is used to show an example of perceptual learning effect in which some conditions of preexposure distributed by the intermixed arrangement enhance how serious an organism discriminates a stimuli. Discrimination and generalization usually take place in every day activity.

Complete discrimination tends to occur when there is conditioned response to a reinforced or conditioned stimuli; there is no conditioned response as a result of response to other conditioned stimuli elicited by others. Generalization occurs as a result of conditioned response to a reinforced conditioned stimuli transferred completely to other conditioned stimuli. For instance, generalization can occur if a person tastes two similar products that have common features like coca cola and Pepsi.

Discrimination entails a situation where an organism learns to distinguish features of similar stimuli and it is aided by exposure in which an organism can compare the stimuli to other.

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