Why did the researchers change the appearance and movement of the climber block in the second experiment?

Listen to part of a lecture in a psychology class.
Professor: Now when the last class ended, we were talking about how we evaluate other people, how we look at other people, and determine which people are likely to be helpful to us, and which people are likely to hinder us as we go through life. And we noted that the ability to distinguish between these two kinds of people, to perform what we call social evaluations, is critical to our survival. Karen, I see you have a question?
Student 1: I’d like to ask if that is learned ability or something we’re born with?
Professor: Well, there’ve been studies that suggest that we are born with a certain capacity for social evaluation, that infants as young as six months are able to make social evaluations. David?
Student 2: I don’t doubt that that’s possible, but at six months, babies are still preverbal, so...
Professor: That’s a good question. One of the studies I’m referring to consisted of two experiments done by researchers at Yale University. In both experiments, the researchers looked at a group of six-month-olds. To prepare for the first experiment, the researchers constructed a little stage, and on that stage, they constructed a little hill, ok? And then they got three wooden blocks: one in the shape of a circle, one in the shape of a square, and one in the shape of a triangle, ok? And on each of these blocks, they glued a pair of eyes, little circles with black dots in them that looked like eyes, ok? So in the first phase of the experiment, the researchers showed the infants a series of brief scenarios. In every scenario, one of the blocks, let’s say the circle block, played the role of a climber trying to get to the top of the hill, ok? So the circle block was the climber. At first, the climber block would appear by itself and start climbing up the hill, but it would be struggling. Then in some of the other scenarios, one of the other blocks, let’s say the square, would appear and would always help the climber block get to the top of the hill, gently nudge it up the hill, ok? So you had the square block always helping the climber block and in the rest of the scenarios, the other block, let’s say the triangle, would appear and would always hinder the climber block. It would always block the climber’s path and force it back down the hill, so the triangle block was always hindering the climber block. Ok, so that was the first phase. Then in the second phase of the experiment, the researchers placed the helper and hinderer blocks in front of each infant and they noted which block each infant reached for.
Student 2: What was the purpose of that? Was it to reach for the helper block?
Professor: That’s right, and that’s exactly what happened in almost every case. Karen, I see you have another question?
Student 1: I’m wondering how you could be sure that they’re choosing based on social evaluation. I’m mean, maybe they just like circles better than squares, or maybe they just like to see things going up the hill more than they like to see things coming down the hill or something.
Professor: Excellent question, which is what the researchers were obviously wondering as well because, as I mentioned earlier, they did a second experiment. They took another group of six-month-olds and showed them scenarios very similar to the ones in the first experiment. Everyone clear on this point? Ok, I’ll continue. Well, only this time, the climber block didn’t have eyes and it never moved by itself. It only got pushed up the hill by one block, very gently, very smoothly and down the hill by the other block very gently, very smoothly.
Student 1: So in the second experiment, the idea was that the babies wouldn’t perceive the climber block as a living thing and it wasn’t trying to do anything, so it couldn’t really be helped or hindered.
Professor: Exactly.
Student 1: So then there wouldn’t be any social evaluation involved.
Professor: Exactly! And what’s more, this time, when the researchers offered the infants the wooden blocks, they didn’t have a clear preference.
Student 1: That’s very interesting.
Professor: What’s considered most significant about these studies is not so much that the infants were able to make social evaluations, but that they were able to evaluate interactions between unknown individuals, interactions that had nothing to do with themselves. That’s pretty sophisticated.
Student 1: Sure is, especially for a six-month-old.