Interesting psychology experiments 3: Contagious yawning works with dogs



If you have a dog you probably know that dogs yawn now and then. But did you ever notice that they yawn as a response to your yawning? This phenomenon is well known between humans as “contagious yawning”, but recent research indicates that even dogs can “catch” human yawns.

In 2008, Joly-Mascheroni et al. conducted a study investigating whether human yawns can elicit dog yawns. To test this, an experimenter was together in a room with a dog, the owner being behind the dog. For five minutes, the experimenter tried to make eye-contact with the dog and started yawning when eye-contact was established. This was repeated over and over again, causing most dogs to yawn at some point during this period. In the control condition, the procedure was similar, apart from the experimenter performing “non-yawning mouth opening actions”.

The results were the following: 21 out of 29 dogs yawned in the yawn-condition while no dogs yawned in between the sessions or during the control condition. The dogs yawned after a mean time of 1 minute and 39 seconds. This is strong evidence that contagious yawning also exists between humans and dogs.

The researchers note that their results allow for different interpretations. Previous research indicated that dogs yawn during stressful situations. In this case this would mean that the yawning condition was somehow stressful for the dogs while the non-yawning condition was not. The other interpretation is that contagious yawning between dogs and humans is empathy-mediated. This would be supported by the fact that more empathic people respond more strongly to other people’s yawns in experiments with humans and by evidence that dogs are surprisingly good at understanding human social cues.

Some studies were performed afterwards yielding mixed results, supposedly due to varying methodology, such as using video-taped yawns. In 2013, Teresa Romero et al. conducted a study directly addressing the interpretation problem mentioned above. To address these issues, they had the owner and a stranger perform yawns to test whether owners can elicit more yawns, which would be expected by the empathy-interpretation. Furthermore they measured the heart rate of the dogs to assess whether the yawning-condition was stressful to them.

Their protocol for yawning vs. non-yawning conditions was similar to Joly-Mascheroni et al. The results showed that significantly more yawns were observed with the owner yawning compared to a strange experimenter yawning. Furthermore the heart rate data demonstrated that the situation was not stressful for the animals. This strongly favors the empathy-mediated interpretation of contagious yawning between humans and dogs.

Because the research on this topic is still relatively young, the mechanisms involved aren’t yet understood. For example, Teresa Romero et. al. mention that the evolutionary origin of contagious yawning between humans and dogs is unknown. It is especially difficult to interpret that dogs show contagious yawning together with humans but not together with other dogs. Thus, further research is required to address such questions.

I would be interested to know whether you can make your dog yawn by repeatedly yawning while making eye contact; I actually managed to do so. Please let me know in the comments.

This post is part of the blog post series “Interesting psychology experiments”.
See also:
Interesting psychology experiments 1: The marshmallow experiment
Interesting psychology experiments 2: Car crash study

Joly-Mascheroni RM, Senju A, Shepherd AJ (2008) Dogs catch human yawn. Biology Letters 4: 446–448. doi: 10.1098/rsbl.2008.0333

Romero T, Konno A, Hasegawa T (2013) Familiarity Bias and Physiological Responses in Contagious Yawning by Dogs Support Link to Empathy. PLoS ONE 8(8): e71365. doi:10.1371/journal.pone.0071365

Interesting psychology experiments 2: Car crash study


In 1974, Elizabeth Loftus and John Palmer from the University of Washington conducted two experiments [1] investigating the effects of the words used in a question about an event on the memory the participants had of this event.

In the first experiment, the participants were shown several car crashes and were afterwards asked to estimate at which speed the cars collided. Previous studies indicated that humans are surprisingly bad at estimating the speed of cars. After watching films of cars colliding, the participants were given a questionnaire concerning the accident. One question was “About how fast were the cars going when they X?” X was the variable in this case. The participants were divided in five groups, all having a different ‘X’ in their question: (1) contacted, (2) hit, (3) bumped, (4) collided and (5) smashed. The hypothesis was that the choice of verb can have an influence on the speed estimated.

Their results indicate that this was the case; the choice of word had a statistically significant effect on the speed estimate. The largest difference was found for ‘contacted’ vs. ‘smashed’ (about 9mph). While these results confirm their hypothesis, it is unclear whether this was merely due to response bias or due to a real modification of the memory the participants had of the accidents.

Therefore, a second study was conducted: Participants watched a film of a multiple car accident and filled out a questionnaire, again including a speed estimate, afterwards. This time, the participants were divided in three groups: (1) One group being asked about the speed during the accident using the verb ‘smashed’, (2) one group being asked about the speed during the accident using the verb ‘hit’ and (3) a control group not being asked about the speed during the accident at all. The speed estimates for ‘smashed’ vs. ‘hit’ were again significantly different, as expected on the basis of experiment one.

One week later, participants were asked to fill out another questionnaire including several questions concerning the accident. One of these questions was: “Did you see any broken glass?” There was no broken glass on the film, but the hypothesis was that the ‘smashed’ group might report having seen broken glass because they estimated the accident to occur at a higher speed – making the involvement of broken glass more likely. Their results confirmed this: People in the ‘smashed’ group were significantly more likely to report having seen broken glass than people in the ‘hit’ and ‘control’ groups.

This suggests that a memory of an event can be modified by things as simple as different wordings in questions about the event. While this particular study suggests high flexibility of memory, it is difficult to draw conclusions from it for real life events because it occurred in a laboratory study, including only films of accidents. As noted here [2], there was a study concerning eyewitness testimony showing relatively constant and accurate memory of an emotional event over time. This casts doubt on whether memory is as flexible as the Loftus and Palmer experiments suggested if important real life events are concerned.

This blog post is part of the series “Interesting psychology experiments”.
See also:
Interesting psychology experiments 1: The marshmallow experiment
Interesting psychology experiments 3: Contagious yawning works with dogs

[1] Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of auto-mobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behavior, 13, 585-589
[2] McLeod, S. A. (2010). Loftus and Palmer

Interesting psychology experiments 1: The marshmallow experiment


In the late 1960s, Professor Walter Mischel from the Stanford University started a set of studies investigating delayed gratification in young children. [1]  In the original studies, the procedure was the following: Children, between 3 and 5 years old, were given a marshmallow and were told that they would get a second marshmallow if they wait long enough and don’t eat the first one. The time until the child started eating the marshmallow was measured, the upper limit being 15 minutes because then the experimenter came back with the promised second marshmallow.

Interestingly, follow-up studies showed that the duration of time the children waited for the second marshmallow correlated with the achievements of them many years later. Children who waited longer than others in this experiment tended to  have more success in school, higher SAT scores, lower BMI (Body Mass Index), higher income and more successful marriages later in life.[2]

The common interpretation of these findings was that self-discipline is the factor causing the different times children are waiting during the experiment. The idea behind this is that high self-discipline carries on into later life and enables the children to have a more successful life.

This interpretation was questioned by a recent study with a relatively low sample size. This study wanted to investigate whether rational decision making in the form of the assessment of the reliability of the environment is also an important factor. Previous studies indicated that uncertainty about the arrival of the second marshmallow decreases waiting time. This study specifically intended to test the difference in waiting times for two different conditions: The reliable and the unreliable condition. Their hypothesis was that children in the reliable condition will view the situation as more reliable and therefore wait longer, the opposite being expected for children in the unreliable condition.

The researchers changed the protocol to include the reliable and unreliable conditions in their experiment: Before starting the actual marshmallow task, they completed two different aspects of the experiment. First, the experimenter brought a very limited set of crayons and a piece of paper to the room where the child was sitting and said that he could bring additional crayons from the other room. The child naturally wanted more crayons and in the reliable condition they received those soon while in the unreliable condition the experimenter apologized and said that no additional crayons were in the other room. This was repeated with a sticker: In the reliable condition the experimenter brought a larger sticker from the other room while in the unreliable condition the child had to use a smaller sticker despite being promised a larger one. Afterwards the marshmallow task was completed in the way described above.

Their findings were statistically highly significant: The children in the reliable group waited for a mean time of 12 minutes and 2 seconds while the children in the unreliable group waited for a mean time of 3 minutes and 2 seconds. This supports their hypothesis that the child’s assessment of the reliability of the situation is a contributing factor to the duration of time waited.  This also has implications for the original findings: Depending on the background of the children their belief in the reliability of the world can differ, resulting in a different duration of time they wait. While this doesn’t imply that self-discipline isn’t also a contributing factor, it indicates that it’s not the only one.

To sum up, the marshmallow experiment is a surprisingly efficient predictor of the success of children later in life. Early interpretations of this included mainly self-discipline as the cause of both the longer waiting time and the later success in life while a recent study suggests that the explanation is a more complex one and has to include the ability to make rational decisions.

This blog post is part of the series “Interesting psychology experiments”.
See also:
Interesting psychology experiments 2: Car crash study
Interesting psychology experiments 3: Contagious yawning works with dogs

Photo source: wikimedia

Two new blog post series

I’m delighted to announce that I’m going to start two new blog post series now. The first one will be called ‘Myths about veganism’, dealing with and commenting on several common myths such as ‘vegans don’t get enough protein’ or ‘cows have to be milked’. This way I hope to bring the truth or untruth behind these myths to the attention of more people. I’ll post on one myth at a time so I’m able to go into some detail without making too long posts. 

While veganism and animal rights are very important to me, I don’t want this blog to be solely about these topics, so the second blog post series is going to focus on another interest of mine: Psychology. It is going to be called ‘Interesting psychology experiments’ and will go into some depth about such experiments – again one at a time. 

While I already have several posts in mind for both blog post series, I’m open to suggestions, so if you know a vegan myth or a psychology experiment you would like to see me write on, please let me know in the comments. Don’t forget to ‘follow’ in order to see these upcoming blog post series. 

Eating animals makes us deny their mental capacities, research shows

seagull-249638_1280As a follow-up on “Why we don’t eat certain animals” where I lined out some reasons for an unjustified asymmetry in our treatment of animals, I decided to make a post on two publications showing psychological effects potentially involved in meat consumption such as denial of mental capacities of edible animals among meat-eaters. 

Dr Steve Loughnan from the University of Melbourne and colleagues conducted a study [1] investigating the hypothesis that eating meat but at the same regarding animals as deserving ethical treatment results in cognitive dissonance. Their experiment tested and confirmed that people who recently ate meat are less likely to attribute a high moral status to animals.

The experiment included two groups of participants: One group ate beef and the other group ate nuts. Afterwards all participants were asked to complete a questionnaire on the moral treatment of animals and specifically cows. Their results demonstrated that people who were in the ‘meat-condition’ chose significantly fewer animals as deserving moral concern and also rated cows as deserving significantly less moral concern. While the ‘meat-condition’ did not make participants attribute fewer sensations to cows, it was observed that attributing a reduced moral status to cows correlated with attributing fewer sensations to them. They argue that this “dementalization” justifies the reduced moral status on a psychological level. 

In follow-up studies [2], Loughnan and colleagues showed that animals which are generally considered appropriate to eat are rated as having “less mind” than those who are not. Furthermore, they found that meat-eaters attributed less mental capacity to animals upon being reminded that these animals suffer for meat production as compared to not being reminded of that fact. Finally, they confirmed the dissonance hypothesis previously mentioned by finding out that people who were told to think about meat-production tended to deny mind to edible animals: This was only the case for the group of participants previously told that they would eat meat afterwards – the control group ate an apple afterwards and no significant link was observed. This denial of mind could according to the authors be a psychological mechanism to deal with the dissonance caused by knowing about the conditions in meat-production but eating meat soon nevertheless. 

[1] Loughnan, S., Haslam, N., & Bastian, B. (2010). The role of meat consumption in the denial of moral status and mind to meat animals. Appetite, 55, 156-159
[2] Don’t Mind Meat? The Denial of Mind to Animals Used for Human Consumption Brock Bastian, Steve Loughnan, Nick Haslam and Helena R. M. Radke Pers Soc Psychol Bull published online 6 October 2011