INTRO TO PSYCHOLOGY
Set #1 (Lectures 1, 2, 3)
1 Lecture 1
September 1 2009
For most of recorded history going back to the Greeks and even further, humans tried to
understand the world. They looked up to the stars and they tried to figure out what they are and
what that means about where they are and whether the earth is turning around the sun or the sun
is turning around the earth and so on.
In the last 200 years or so theres been a dramatic shift compared to all the recorded history
before because in those two centuries human curiosity has laid open many of the mysteries that
humans were contemplating for thousands of years. Its only in the last 200 years that these
mysteries have become open books to us: things like nature and structure of space and time.
The constitution of matter, the many forms of energy, the nature of life itself with the discovery
of DNA and the decoding of human genome. Those of the things in Aristotles time or in
Newtons time wouldve seemed unimaginable that weve come this far.
One of the last frontiers, one of the remaining mysteries is the human mind and the nature of
human thought, human conscious experience and human behavior. And in the last 20 years,
weve seen an explosion of research in psychological science and one of the things that I want
to emphasize is that psychology as itll be taught in this course and in our department
psychology is a science. Some of you are enrolled in the arts. If you look on the McGill web
page or McGill course offerings bulletin, youll see that psychology is in the faculty of science,
not in arts.
Psychology is an empirical science like biology and physics and chemistry and that means
something. Some of you are probably attracted to this course, I know because Ive talked to a
few of you, why you decided to take the course, Well Im not sure what Im going to major in
but my friends tell me that Im pretty good helping their problems and so I figured I can learn
more about human behavior and since my friends come to me for help and Im usually a source
of good advice, I figured that Im talented in that area. Now, that is something and it has
something to do with psychology, but it has very little to do about what were going to talk
about in this course.
Let me tell you whats different. Psychology is an empirical science. By empirical, I mean, its
evidence based. And the evidence has to be in a certain form; the evidence has to be objective,
it has to systematic, it has to be repeatable and the topic of the lecture on Thursday is what it
means to do an experiment in psychology.
It has to be repeatable: if youre giving your friend advice and they follow it, its not really an
experiment because its not repeatable. They could follow your advice this time and not follow
it the next time and thats becoming more like an experiment, but of course the circumstances
2 are different the second time. You dont have exactly the same conditions which to study your
ability to give good advice. If you give advice to 10-20 people, and you could manipulate the
advice by telling half of your friends to do the opposite of what youve told to the other half,
but the situations arent the same and people arent the same so thats not really an experiment
A real experiment gives you control over the variables. So take an analogy when the
weatherman tells you that they think its going to rain tomorrow. Thats not a repeatable
experiment, theres only one tomorrow and theres only one set of conditions exactly like they
are today. So when they talk about an 80% chance of rain, its not technically a statistical
judgment as we normally think about statistics and probabilities. Really what it is, is the
weather person telling you how confident they are, which is something different. If you had a
1000 worlds exactly like the Earth, and 1000 weather person, making 1000 predictions about
all those worlds and the conditions were the same in each one, then thats more like an
experiment. But we have a single weather person, making a single prediction about a single
day. 80% means Im pretty sure you should bring your umbrella because youll be upset if you
dont. 30% means you probably dont need your umbrella, but it doesnt really mean 30% in
the sense of a statistical regularity. It doesnt mean 30% of the time the weather person says its
going to rain, when they say 30% it does rain.
Well, what is an experiment? An experiment might be that you have 50 people coming to the
laboratory and you show them some words on the screen and you suddenly change the
brightness of the words and you see at which point they can no longer name the words, because
the words arent bright enough on the screen anymore. Its replicable because you can do this
as many times as you like. Its objective because you can measure they either can read the
words or they cant. Its not up to your opinion whether they can read a word, its an objective
measure. Its systematic; youre changing the luminance in a particular formulaic way each
time. Its an experiment where youre using evidence, empiricism and the scientific method.
Psychology, thus, is an empirical science. We follow the scientific method. As a preview of
Thursday theres a hierarchy in science. Good experiments to bad experiments and it supplies
to all the empirical sciences; chemistry, biology, physics, genetics and psychology, theres a
hierarchy. And youll read about it in chapter 2. Id like you to read chapter 1 for next time.
Part of science is observation. When youre just beginning to investigate something, the careful
scientist simply observes what it is about the world and collects the information without any
preconceptions. So, its a type of experimentation, but observation and description could be
important. For example, you might want to know whether there are any downy woodpeckers in
3 Montreal. You set up in a habitat where youre expecting to find them and you just wait, you
see if there are downy woodpeckers and you count them. Thats a descriptive study.
One of the tenants of scientific research reasoning is that you cant prove a negative. You can
provide confirmatory evidence. If you spend a day in Mont-Royal Park and you dont see a
downy woodpecker, youd be foolish to conclude that there are no downy woodpeckers in
Montreal. You can say you didnt see them in that particular day and that particular time. You
can have a hypothesis that there are none and then you can reject that hypothesis as soon as you
see even one. Theres an asymmetry here in your scientific reasoning. Not seeing anything
doesnt prove anything. Seeing even one though does prove something, it proves theres at least
As a philosopher of science, Fimpel used to say you cant prove that there are no unicorns; its
just that you havent seen one yet. There can always be one hiding in a cave somewhere and as
soon as you find it than youve disproved the hypothesis.
You can gather evidence in a variety of ways. Consider that not all observational experiences
are equal. If I set up in Mont-Royal Park, looking for my precious downy woodpecker, and I set
up for one day and I dont see it, compare that experiment to if I take all of you and I ask all of
you to scatter yourselves around the Montreal area. Compare that to the one person in the park.
Even though youre not putting any quantitative data on, it feels like a better experiment. It
feels like if there is one out there we got a better chance of finding it. The sheer number of
people placed in number of places represents more likely to turn one up.
And even better experiment, if I pay you $10 for every one you find and document with a camera
so I know that youre not making it up. Thats better because now I know that youre
motivated. This is still a descriptive study.
Another kind of study is a correlational study. This is where we observe two variables that
change together but we dont necessarily know which one is causing the other. Correlational
experiments are often second kind of experiment that you do after an observation.
So lets say I put all of you out in different parts of Montreal and all of youre looking for downy
woodpeckers, and you come back and maybe 10 of you found a bunch of downy woodpeckers
and all 10 of you, it turns out were near blue spruce trees and there was no instance of
somebody finding a woodpecker where there werent blue spruces. Now I can form a
hypothesis that maybe downy woodpeckers like blue spruce trees and I can concentrate my
efforts on the blue spruce.
What we have is correlation. We dont know that the blue spruce causes the downy woodpecker
to be there. We dont think that the downy woodpecker caused the blue spruce to be there. You
can have some idea that the causation works in one direction versus the other, but all we have is