How do you feel about the photo to the left? As for me, I hate looking at it, so I made it as small as possible! I am not snake-phobic, but like many other humans, I'd much rather pick up a rabbit or even touch a bear than pick up a snake. But where'd I get that fear? To what extent is humans' fear of certain creatures–like snakes or spiders–present when we are born?
Several groups of researchers have been exploring this question in humans and other primates. The results of one study have been covered by National Geographic's news site. Read this description of the study by the journalist:
Forty-eight six-month-old infants were tested at the institute to analyze how they reacted to images the researchers predicted might be frightening. While sitting on their parents' laps, infants were shown images of spiders and snakes on white backgrounds for five seconds. To prevent parents from inadvertently influencing their infants' reactions, they were given opaque sunglasses during the experiment that prevented them from viewing whatever image was shown.
…When the babies saw pictures of the snakes and spiders, they consistently reacted with larger pupils than when they were shown control images of flowers and fish.
a) What seem to be the independent and dependent variables in this experiment? (By the way, why was this an experiment rather than a correlational study?)
b) Based on the description of the study, was this experiment independent groups or within groups? How do you know?
c) Which of the four basic types of experiments was this: Repeated measures? Concurrent measures? Posttest only? Pretest/posttest?
d) Sketch a graph of the results of the study.
e) The parents were given opaque glasses to wear while holding their babies. Which of the four big validities will this step help to improve?
Now, let's focus a bit on what it means when a baby's pupils dilate. Pupil dilation was the operationalization (the operational definition) of the study's dependent variable. But what construct does pupil dilation supposedly represent? Given the story's headline, you might think the construct is "fear." But it's probably more complicated than that. Read on:
…. dilated pupils are associated with activity in the noradrenergic system in the brain, the same system that processes stress. Closely measuring changes in pupil size has been used in previous studies to determine a variety of mental and emotional stress in adults.
But the journalist also noted:
…it's difficult to characterize the exact nature of the type of stress infants experienced, but dilated pupils show heightened states of arousal and mental processing. Rather than indicating fear in particular, the study says this shows an intense focus.
f) Based on this description, what are some of the candidates for the construct measured by pupil dilation? (You can also read even more correlates of pupil dilation here).