Forty-eight of the 51 students in the evolutionary principles of health course completed all surveys at both pre- and post-semester (94% response rate). Of the three students not completing the surveys, two students did not complete the surveys at pre-semester and the other left college before the end of the semester. In the control course, three students’ responses were eliminated because these students reported that they were simultaneously enrolled in a course on evolution. Three additional students did not complete the pre- or post-surveys for unspecified reasons. Therefore, the control group was comprised of 26 students that completed all surveys at pre- and post-semester (90% response rate).
The following analyses included data from the evolutionary principles of health course only, henceforth referred to as teleology intervention (TI). Four percent (4%) of the students were sophomores, 36% juniors, 56% seniors, and 4% post-baccalaureate students. Prior to this course, students reported taking a mean (SD) = 0.43 (0.64) courses on evolution in high school and a mean (SD) = 1.25 (0.79) courses in college. On 5-point Likert scales students self-scored their prior educational exposure on evolution as a mean (SD) = 3.27 (1.25) and scored their parents’ attitudes toward evolution as a mean (SD) = 3.38 (1.23). Self-reported religious affiliation included: 10% Catholic, 0% Eastern Religion, 14% Fundamental Christian, 4% Jewish, 0% Muslim, 24% None, 16% Other Protestant, and 32% reported Other. On the importance of religion in the students’ lives, 38% listed “not important,” 20% “slightly important,” 16% “moderately important,” and 26% listed “very important.”
Pre-semester data
At pre-semester, students in the TI course with lower levels of teleological reasoning had higher understanding of natural selection (i.e., higher CINS scores) (r=-0.65; p<0.0001) (Table 1). Students with lower levels of teleological reasoning had higher acceptance of evolution (r=-0.44; p=0.0017) and lower religiosity (r=0.35; p=0.014). Students reporting that their parents had more positive attitudes toward evolution had higher acceptance of evolution (r=0.58; p<0.0001). There were no differences between the TI course and the control course on any measure at pre-semester (see Additional file 3).
To control for all other variables and illustrate the relative influence of each variable (parental attitude, religiosity, prior education, teleological reasoning, and natural selection understanding) on students’ incoming acceptance of evolution (I-SEA), we conducted a multiple linear regression (Table 3): R2 = .45; F(5, 42) = 6.88, p<0.0001 (Adjusted R2 = 0.38). Together, these variables accounted for 38% of the variance in student acceptance of evolution scores, with significant unique variance contributed only by parent attitude toward evolution (positively).
Multiple linear regression determined the relative influence of each variable on student understanding of natural selection (CINS without the six teleology questions) prior to instruction (Table 4): R2 = .42; F(5, 42) = 6.02, p<0.00028 (Adjusted R2 = .35). Together, these variables accounted for 35% of the variance with significant unique variance contributed by incoming teleological reasoning (negatively). To summarize, parental attitudes toward evolution were the greatest predictor of students’ acceptance of evolution and teleological reasoning was the main predictor of natural selection understanding, prior to instruction.
Pre-post comparisons
Wilcoxon signed rank tests examined whether variables changed in response to the course material (Figure 1). Students improved their understanding of evolution (CINS without the six teleology questions) (MPre=9.00 (2.92); MPost=10.27 (2.35); Hedges’ g=0.48; P=0.0001). CINS score increased in 64.5%, stayed the same in 12.5%, and decreased in 23.0% of students at post-semester compared to pre-semester. Students’ endorsement of teleological reasoning decreased over the course of the semester (MPre=3.00 (0.80); MPost=2.00 (0.87); Hedges’ g=1.20; P<0.0001). Student endorsement of teleological reasoning decreased in 96% of students and increased in two students. The decrease in endorsement of teleological reasoning is consistent with a significant improvement on the six CINS questions which had teleological themes or distractors (MPre=2.15 (1.83); MPost=3.54 (1.81); Hedges’ g=0.76; P<0.0001). Student acceptance of evolution (I-SEA) increased (MPre=100.50 (15.55); MPost=106.70 (13.75); Hedges’ g=0.42; P<0.0001). Acceptance of evolution increased in 70.8%, stayed the same in 14.6%, and decreased in 14.6%, of our sample. Similarly, student acceptance of human evolution (I-SEAHE) increased (MPre=32.65 (6.63); MPost=35.40 (5.38); Hedges’ g=0.46; P<0.0001). Student level of religiosity did not change during the semester. No significant changes were observed on any of these measures in the control group (Additional file 3).
Post-semester data
Natural selection understanding at post-semester was significantly correlated with post-semester measures of teleological reasoning (r=-0.38; p=0.0074), student religiosity (r=-0.39; p=0.0064), and acceptance of evolution (r=0.39; p=0.0068). Higher student religiosity was associated with lower levels of understanding of natural selection (r=-0.38; p=0.0064) and lower levels of human evolution acceptance (r=-0.53; p<0.0001). Students with lower levels of teleological reasoning had higher acceptance of evolution (r=-0.44; p=0.0017).
We conducted a multiple linear regression to determine the relative influence of each variable, independently of the others, on the post-semester natural selection understanding (CINS) score. Overall, 45% of the variance was explained (Table 5): R2 = .52; F(6, 41) = 7.40, p<0.0001 (Adjusted R2 = 0.45). Only pre-semester natural selection understanding (p<0.001) contributed significant unique variance.
Reliability and criterion validity of measures
As a measure of internal consistency for the CINS, Cronbach’s alpha was 0.81 at pre- and 0.77 at post-semester. For the teleology survey used in this study, Cronbach’s alpha was 0.91 at pre- and 0.89 at post-semester. For the I-SEA, Cronbach’s alpha was 0.95 at pre- and 0.96 at post-semester. The scores from the 36-item teleology measure based on Kelemen et al (7) significantly correlated with incorrect responses from the six teleology-themed questions on the CINS at pre- (r=0.48; p=0.0006); and post- (r=0.53; p=0.0001) semester.
Qualitative analysis
Two raters independently scored each student response to the four open-ended questions during the tenth week of the semester to determine each student’s level of acceptance of evolution, using a 5-point Likert scale. Kappa’s interrater reliability was 0.95. The raters discussed the slight scoring differences and agreed on consensus ratings, where 69% of students completely accepted evolution, 16% mostly accepted evolution, 12% had neutral/unknown evolution acceptance, 4% mostly did not accept evolution, and 0% completely did not accept evolution.
The thematic analysis of the responses to the open-ended questions revealed that 69% of students mentioned that teleology was a new concept to them during this course. The lack of awareness of teleological reasoning in students’ own thinking is shown in representative quotes below.
"I had never previously heard of teleological statements before this class. It's interesting to change my cognitive process of automatically attributing a purpose to the existence of things."
"My use of the term teleology was non-existent before I took this class[…]teleology was nowhere to be found in my personal lexicon until I encountered the word in this class."
"I have been seeing life in a less teleological way. I was new to the word teleology."
"Before this class I didn't know what teleology was. I think it is a very interesting concept that I definitely accept like most of the things in this class."
“I am now able to look at evolution through a biological perspective which has helped me to really solidify my understanding. I have also begun to attempt to not think teleologically about evolution, which is something I had no concept [of] before this class.”
The vast majority of students (84%) mentioned that, as a result of the course, their use of teleological thinking/awareness has changed or decreased and that they are now more aware of evolutionary mechanisms as causal factors, rather than an end goal, functionality or purpose, as causal factors in evolution. For example,
"My cognizant awareness of how teleology infiltrates thinking about how the world works has increased over the course of this class. It is so easy to fall into teleological reasoning, as if an intelligent designer crafted the material universe. However, I don't believe in such a creator, so it is important for my language to accurately reflect my perspective."
"I find it fascinating how my way of thinking has changed. Instead of just thinking of the purpose of our lives I have become more aware of the causes as well."
The majority of students viewed thinking non-teleologically about human evolution to be a persistent challenge during the semester. 71% of students mentioned that it is easier for them to think that evolution has a purpose and more difficult to think about evolution as a random, non-directed process.
“It is very easy to think of evolution as having a purpose and direction, so the idea that it is random was the hardest part for me to grasp.”
"I still have a difficult time understanding the non-teleological way of thinking in evolution and the ideas of unguided, directionless occurrences."
“At first, thinking teleologically was very hard not to do and it was slightly confusing to refrain from this way of talking and thinking because it felt like the logical, natural way to explain things.”
“There always seems to be a way to find exceptions to this non-teleological way of thinking and this was also evident in our class discussions. Natural selection being a completely random process does not make much sense to me since the goal is always to influence reproduction in a positive light. To me, evolution seems very purpose driven. If it was completely random and purposeless then isn’t there a chance that the least fit individuals might be able to survive some of the time? There is a lot of research and information about teleology that I would love to read about and learn more from, but to be honest I struggle immensely to not see the purpose behind it. I believe that natural selection is a real process, but couldn’t it also be a beautifully created process designed to help the fittest individuals adapt and survive? If it is really true that we are here completely by chance, and there was and is no real purpose for our own individual lives, then why does anything we ever do matter? Why would having a moral code matter? It is these questions I had to ask myself when we talked about this topic, and it is for these reasons I believe teleology to be impossible to reject.”
“It is still so hard for me to not think teleologically when thinking about evolution. I feel like everything is supposed to have a purpose, but when really its just natural causes, and that we evolved this way by chance. I will say that my use of teleology has changed, but I still continue to use teleological statements because I was just raised to believe that everything happens for a reason.”
Over a third of students (37%) mentioned that they viewed teleological thinking as a potential obstacle to learning/accepting evolution.
“It is very hard to not think of things as having a cause or reason behind them. I'm still slipping and it seems like everyone in this class does as well.”
“We have a hard time thinking of things as natural and random, probably because you have to extend your thoughts past the human lifetime, to a more grand overarching idea about life. I definitely understand that nature does not have a purpose, but sometimes it's easy to explain things as if it does have a purpose for simplicity.”
“I think it is difficult for humans to avoid attributing purpose to natural occurrences within nature because knowing the cause of everything helps us feel as though we have a better grasp on the way things are. […]Being in the course has transitioned my use of teleological thinking because I agree that it causes misunderstanding and misconceptions of the occurrence of natural events.”