Does previous experience influence our perception?


The experiment took place in order to investigate the effects of previous events on perception, in this case it was seeing a picture which was either a group of animals or a group of people and then later when shown a picture participants had to describe what they had perceived. The null hypothesis for this experiment is that there will be no correlation between the pictures that the participants were originally given and the way in which they perceived the second image. The alternative hypothesis however is that there will be a difference depending on which images were seen by the participants. The experiment was used to investigate various theories about perception such as that from Vernon 1955 who described the ‘Perceptual Set’ and said that it worked in two ways.  The first is where the perceiver has certain expectations, in this case due to the image already seen and therefore will focus their attention on particular aspects of sensory data. He calls this the selector. The second part is where the perceiver knows how to classify name and interpret certain data and therefore know what to draw from it, he calls this the perceiver.  The main aim of this experiment however is to replicate the study of perception conducted by Bugelski and Alampay who investigated the importance of expectation in the perceptual set, they found that those who had previously been shown images of animals were more likely to see the stimulus as being a rat because they had preconceived expectations. The other aim is to understand the conventions for writing psychological investigations using a simple experiment in order to practice this.


In order to test this a sample involving the whole of the psychology class was taken making it an opportunity sample, some of the class were given stimulus cards depicting animals where the rest had cards with people on. This therefore used the experimental design of independent groups because there were two groups with different stimuli.  The actual picture was then put upon the board and each participant was asked to write down what they had seen. In this case it was likely to be either a man or a rat depending on the stimulus they have previously been given. The results were then interpreted using chi square which is a statistical test that allows accuracy of results to be seen.

This is the formula for chi squared:


Here is an example of the stimuli given:


Participants were able to give consent because it was made clear that they didn’t have to participate and could remain anonymous if necessary. On the other hand informed consent could not be given because this would affect the results of the experiment as demand characteristics could be displayed making them less reliable. A debrief was carried out however which explained why the experiment had taken place meaning the experiment was fairly ethical due to these measures.

Here is a table of the raw results seen in the experiment:


Here is the table of the raw results inputted into the chi squared equation:



The results could be described using Gregory’s theory of indirect perception which states that people base their perceptions on prior knowledge and past experiences hence why the participants used their previous knowledge of the stimulus to base their perception upon. Gregory says that perception occurs as a result of hypothesis testing where the brain attempts to guess and process the image based on information previously stored in long-term memory. Here in these results however there appears to have been a fault in the perception which he would explain to be due to a faulty hypothesis hence the differing perceptions although there is still a weak correlation. So to conclude, although using chi squared the results appear to be insignificant, we can see results which begin to prove the alternative hypothesis that perception is dependent upon the stimulus seen but they are not consistent enough to provide a reliable conclusion.


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