P435 Dosher Attention Chapter Study Guide/HomeworkBusey Spring 2005
Name:
The purpose of this study guide is to help you work through the Dosher chapter, which you can download from the course web site (the complete title is "Models of Visual Search: Finding a Face in the Crowd".
In class on Thursday we worked through the derivations covered in section 10.1.3. If you are a little fuzzy on these predictions, take a look at this section before you continue. The actual equations to predict the reaction times are found in section 10.2.1.
Once you review this section, answer these questions below in a word document and send it to Bethany () by Tuesday's class (2/8)
1) In section 10.2.1, she talks about how the equation for reaction time for target present can be rewritten, starting from:
and then expanding (m+1):
Since doesn't depend on m, we can simply combine and into a new that is different from , the intercept for target absent. This is justified since people tend to have different intercepts for target present and target absent anyway; part of this may come from the fact that people may like to check their answers when they are saying 'no' because they are doing so on the basis of negative evidence.
This gives a new formula for predicted reaction time for target present:
compare this with the predicted reaction time for target absent:
Ignoring the y-intercepts (the alphas), what is the relation between the slopes of the two set size predictions?
2) Based on 10.2.3, how do we know if our predictions correspond to the actual data? Why is it important to compare the predictions to the data?
3) Within Feature Integration Theory (FIT), what is preattentive search and attentive search, how do they relate to feature maps, and what predictions does the model make for feature search and conjunction searches?
4) Read through the selective search sections covered in 10.3.5, 10.3.5.1, 10.3.5.2 and 10.3.5.3. Then look at Figure 10.9. In the graph on the left, subjects were told to attend to red items, and there were always the same number of red items on the display (although not all of them, or possibly any of them, were targets). The x-axis plots the number of items that are not read, and so bigger numbers correspond to larger overall set sizes. As the overall set size gets larger, what would you predict the target present reaction times should do if subjects could perfectly attend to just the red items and ignore the other items? That is, should the times get longer, stay the same, or get faster as the set size increases? What actually happens, and what does this mean about the subject's ability to attend to red?
5) Now answer the same question about the graph on the right, where subjects instead had to selectively search through the O's. What would you predict if they could perfectly attend to all the O's and ignore the other shapes, and what actually happens?