Travis Hallenbeck

PSYC 4120

TA Hope Denney

February 5, 2004

1. see attachment

2. A larger d' was not obtained in the "strong" signal condition (in experiment 3), because I had spent so much time trying to be accurate in the beginning of the experiment that I got tired. Trial 2 especially wore my eyes out, since the space the stimulus appeared in got larger and more was at stake for a mistake. The signal strength stayed the same for all four trials, and I don't understand how the # of windows the signal could appear in could be considered changes in strength.

3. Beta varied with payoffs in the expected directions. Before payoffs, I was slightly conservative (beta=+1.11). But when I got few points for a hit and lost many point for a false alarm, I became much more conservative (beta=+4.60). Also, when I got many points for a hit and lost few points for a false alarm in the third trial, I became more liberal (beta=+1.00). During the last trial I just toggled through it detecting a stimulus every time since lab was ending, so the data from it doesn't represent my sensitivity or bias well. Nevertheless, the beta for the fourth trial is liberal at +1.00.

4. Changing someone's criterion to make them more liberal will increase their hit rate and false alarm rate. They'll say they detected the stimulus if they have only the slightest sense that they saw it, so they will get more hits. But, they are also more prone to confuse noise for the signal and, thus, make a false alarm. Changing someone's criterion to make them more conservative will lower their hit rate and false alarm rate. They are less likely to say they detected the stimulus unless they're very sure, so they will not accidentally detect the stimulus as much. They will also not say they saw the stimulus if they just barely detected it, lowering their hit rate.

5. The observer with the lower false alarm rate is more sensitive, since the one with the high false alarm rate probably just has a very liberal bias.

6. A neutral bias would be appropriate for the inspection of parts coming off of an assembly line, since the parts will probably get casually inspected by many other people before they leave the factory. The appropriate kind of bias also depends on how much you're getting paid and what kind of parts you're inspecting. You might want to inspect parts for an space shuttle or computer more conservatively than parts for clothes or toys. A somewhat conservative bias would be appropriate for security checks for weapons and explosives since you want to catch all weapons and explosives, but if normal people are going through the security check in great numbers, you probably don't want to make them really uncomfortable. A liberal bias is appropriate for the detection of shoplifting by store employees, since you don't want to hassle your customers and accuse them of stealing if they are not. A neutral bias is appropriate for the detection of diseased organs by doctors, because they want to catch everything wrong, but they don't want to amputate or do surgery unnecessarily.

7. In an observer obtains a hit rate of 0% of a stimulus, then the stimulus could be below their absolute threshold. For instance, if you are somewhat blind, your absolute threshold for detecting a visual stimulus is probably very high. Criterion probably has little to do with it unless the observer is confused about what they were instructed to do. Perhaps they don't know what the stimulus is supposed to be.

Color Pre-lab

The three primary colors for light are red, green, and blue. Their components are yellow, magenta, and cyan.

Helmholtz's color matching experiments proved that any color could be created by mixing three wavelengths of light. However, people who are color deficient can match the colors of all wavelengths in the spectrum using only two other wavelengths.

Additive color mixing is done by mixing lights.

Subtractive color mixing is done by mixing paints.

Metamers are two physically different stimuli that are perceptually identical.

A dichromat only experiences some colors.

A monochromat sees everything in shades of gray.

An anamolous trichromat is

Protanopia is a form of dichromatism in which short-wavelength light is perceived as blue until at 492 nm (neutral point) it is perceived as gray. Wavelengths above the neutral point are perceived as yellow.

Deuteranopia is a form of dichromatism in which short-wavelength light is perceived as blue until at 498 nm it is perceived as gray. Wavelengths above the neutral point are perceived as yellow.

Tritanopia is a form of dichromatism in which short-wavelength light is perceived as blue until at 570 nm (neutral point) it is perceived as gray. Wavelengths above the neutral point are perceived as red.