Abstract: Cats positive effects on their owners’ physiological and psychological health, including improved mood and activation of the human prefrontal cortex and inferior frontal gyrus in the brain. However, the association between the health benefits provided by cat ownership and the characteristic behaviors and reactions of cats is unclear. We recruited 29 participants to measure human prefrontal cortex activity, using functional near-infrared spectroscopy, during interactions with a cat. After the experiments, participants subjectively responded to a questionnaire regarding success rates for interactions with the cat, and completed the Self-assessment Manikin—a scale used to measure emotion. Interactions comprised eight types in four categories (touch, play, train, and feed). This study showed that interactions with a cat significantly activated the prefrontal cortex, regardless of interaction type. During training, the integral values of oxygenated hemoglobin in the left inferior frontal gyrus were the highest in all the interaction categories; however, success rates were lower than in the touch and feed interactions. Regarding the Self-assessment Manikin scores, all interaction categories showed a positive correlation between success rate and valence score, especially in the train and play interactions than in the touch and feed interactions. These results indicate that interactions with a cat activate the prefrontal cortex in humans, including the inferior frontal gyrus region. Moreover, cats’ autonomous behaviors and reactions positively influenced the participants. The characteristic temperament of cats may be a key factor influencing the health benefits of owning cats.
Discussion
Sequential change in Oxy-Hb signal of the PFC
Interactions with a cat activated participants’ PFC, regardless of interaction type. The experiment protocol consisted of interactions typical in cat owners’ homes; therefore, this result suggested that owning a cat enhances the function of the owners’ PFC. Furthermore, PFC controls executive function [12]; therefore, interactions with a cat may improve executive function. This result is consistent with previous studies [10][11]. To our knowledge, this study may be one of the first to explain the mechanism that everyday interaction with cats enhance PFC function.
Integral values of the IFG for the train and play interactions
We focused on the integral values of Oxy-Hb signals in left and right IFG regions. In all interactions, the integral values did not correlate with each success rate individually. However, there was a significant difference among interaction categories. The integral values of the train interaction were larger than those of the other interaction categories. Notably, in the left IFG region, the integral values of the train interaction were significantly larger than those of the other categories. The left IFG controls the mirror neuron system [36] and empathy [37]. This study suggested that performing training interactions with a cat would be an effective way to help develop these brain functions.
There are several possible reasons for significant activation of the IFG during the train interaction. First, participants might have not been accustomed to training a cat; thus, it is possible that unnatural interaction situation promoted Oxy-Hb activation for participants. Training is still not a typical interaction between a cat and its owner in general households. Nevertheless, training using clicker has recently become a standard method to improve cats’ welfare [20] and develop effective relationships between cats and humans [38]. Training a cat should be recognized as a common interaction between cats and their owners.
Second, the characteristic temperament of cats (i.e., not typically displaying obedient behavior) might have been the reason for activation of the IFG. For the train interaction, participants reported significantly lower success rates than for the feed and touch interactions. The cat frequently showed autonomous behaviors and reactions to participants owing to the independent nature of cats. Participants might try to anticipate the cat’s next action and determine how to succeed. This thinking process might have been the reason for the activation of the IFG.
The play interaction also showed a lower success rate than did the feed and touch interactions. Further, the integral values of the IFG during playing with the cat were larger than those during feeding. In the play interaction, it was difficult for participants to attract the cat to play. As with the train interaction, participants might think about the way to succeed in this interaction.
The thinking processes used during the train and play interactions related to fundamental nonverbal communication skills necessary not only for interactions between people and animals but also for interpersonal interactions. Therefore, the train and play interactions with a cat, which induce the activation of the IFG, have potential to treat individuals with ASD, which have impaired function in the IFG region [18]. Previous studies showed that interactions with an animal can improve the social communication skills of children with ASD [39][40]. Although much of the previous research has been performed using therapy dogs [41], a few studies have posited that cats can also be useful for therapy with people with ASD [42][43]. However, the mechanism was still unclear.
It is frequently difficult to speculate on cats’ behaviors, even for their owners. The behaviors and temperament of cats, such as independence, is a unique trait compared to dogs. As cat domestication was shorter than for dogs, and may not even be complete [28], the genes of domestic cats are not distinct from those of wild cats [44]; thus, even household cats frequently display autonomous behaviors like wild animals. The present results suggest that cats’ unique behaviors and reactions are the key factors explaining the mechanism underlying the health benefits that cats can provide to individuals with ASD. However, this study targeted healthy participants, not those with ASD; therefore, further studies are needed to determine whether cats positively effects the treatment of individuals with ASD.
Integral values of the IFG for the feed and touch interactions
During the feed interaction, the integral values were significantly less compared to the other interaction types; however, the success rate was higher than in the train and play interactions. Since feeding is the most fundamental interaction between a human and an animal, the cat relatively obeyed participants during the feed interaction. Participants may have felt it was easy to speculate on the cat’s behavioral reactions during the feed interaction; therefore, the IFG region was not activated.
As with feeding, tactile communication with a cat is a central interaction between a cat and its owner. In this study, the touch interaction showed a higher success rate than either the train or the play interaction; however, the integral values of the IFG were larger than during the feed interaction. This could be the result of tactile stimulation. A previous study showed that the IFG region was activated by touching a cat [13], which is consistent with the findings of this study. Therefore, the current results might show that tactile stimuli, which occur through interaction with a cat, affect IFG activation.
SAM
Valence scores from the SAM significantly positively correlated with success rates. The valence dimension in the SAM is the measurement of emotions, such as happiness and satisfaction [32]. In this study, participants felt positive emotion when the cat obeyed them. Moreover, the train and play interactions, which had a significantly lower success rate than the feed and touch interactions, showed a relatively higher correlation coefficient than the feed and touch interactions. Therefore, the present result indicates that the lower the success rate of interaction with a cat, the more likely positive emotions of the participants occurred when the interaction succeeds. As mentioned above, cats and dogs have different temperaments, and cats frequently showed autonomous behavior and reaction for their owners. These characteristic temperaments of cats may be the key factor to enhance human psychological status.
During the play interaction, only the arousal score for the SAM significantly positively correlated with success rates. The arousal dimension in the SAM is the measurement of emotions such as excitement [32]. In the play interaction, the success meant the cat responded to the cat toys using its paws. It is possible that the movement of the cat increased the arousal of the participants. Previous studies claimed that the arousal response is related to enhanced cognitive function [45]. Additionally, exercise, which increases arousal, also improves executive function [46][47]. Therefore, playing with a cat may promotes the development of human cognitive function. Furthermore, 90% of cat owners play with their cats at least once per day [48]; thus, play with cats is a common interaction for their owners. The results of the current study may show the mechanism of an association between owning pets and improved executive functions.
Limitations
This study had several limitations. First, we used a laboratory cat, not a house cat. This was because of the difficulty of conducting this experiment in cat owners’ homes. Domestic cats are territorial animals [49], and would not behave typically with their owner if an unfamiliar person and apparatus were to be in their territory. Thus, we utilized a laboratory cat. However, the cat had been raised in the laboratory like as a house cat; therefore, the cat had the characteristic temperament of a house cat.
Second, during the experiments, only participants could initiate an interaction, not the cat. Specifically, in the touch interactions, we requested that participants pet the cat. However, cats often display allogrooming (i.e., groom other cats using their tongue) and allorubbing (i.e., rubbing their head and tail toward other cats) behaviors toward humans [50]. If interactions between participants and the cat had been mutual, the results may have varied. In future studies, researchers should design a protocol that allows for free and mutual interactions between cats and participants.
Third, we used Bonferroni’s and Scheffe’s methods for post-hoc analyses; although, we did not use a false discovery rate approach. Therefore, further studies should use false discovery rate to control the proportion of false positives among channels that are significantly detected.
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