Guided reading: Understanding an experimental study

We discussed the difference between correlational studies and true experiments.

Let’s take this opportunity to look deeply into one example of a true experiment, one that was carried out by Glenn Schellenberg and published in 2004 by the journal Psychological Science. You can access the article here (note that the article is behind a paywall, check whether you can download it).

As we saw earlier, for a long time, Schellenberg has been interested in understanding whether music training may boost your intelligence. However, the classic correlational approach (i.e., comparing musicians and nonmusicians) was insufficient to provide a sound answer to the question. In this study, Schellenber had the chance to carry out a true experiment.

Recruiting participants

The study was conducted in Canada. We previously mentioned that participants of true experiments have to be selected randomly for the study. So Schellenberg recruited the participants through an advertisement in a local newspaper that offered free, weekly arts lessons for 6-year-olds. Families were asked whether they wanted to participate regardless of the experimental condition to which their child was assigned. Children could be assigned in one of the four conditions: two groups received music lessons, either standard keyboard lessons or voice lessons for one year. Two control groups received either drama lessons or no lessons. The lessons were held once a week, and would start in September, continuing for 36 weeks after.

Dividing the participants

In the end, the study recruited 144 children that were assigned randomly to one of four groups. Note that here, we have one experimental condition divided in two ways (piano and voice) and the classic passive control condition (i.e., a group of children, who for the duration of the training were not involved in any training). This control group is necessary to understand the possible improvement in the experimental group. Children taking part in the experimental group may improve because of a sort of placebo effect.

The control group serves to understand whether the improvement is substantial or not.

Reviewing the results

All groups showed an improvement, and this could be expected, even in the control condition.

Usually, the IQ of children increases with school and age. However, the increment in IQ of the participants involved in the music condition was larger than that of the two control groups: the IQ of participants in the music condition improved by 6-7 points, whereas the IQ of participants in the control conditions improved by only 4 points.

Noticeably, the drama group (i.e. the active control condition) did not improve as much as the music condition, demonstrating that the improvement in the IQ score was due to the music training and not to the fact that participants were involved in some kind of activity.

My own comments

I just have a couple of comments on the present study. As we discussed earlier, this experimental study required an enormous amount of effort: the study lasted a long time, it required a solid economic budget to pay for the music lessons as well as for the control activity. The improvement in the music lesson was indeed observed, but after 36 weeks of music lessons, the IQ of the children in the music conditions improved by only 2 points in comparison to the children in the control groups. Noticeably, although the training was free, some participants dropped the training.