There are psychological benefits to watching fish and crustaceans in an aquarium, according to a new study led by Deborah Cracknell. Cracknell's team observed people’s natural interactions with a marine life display, and took heart rate, blood pressure, and questionnaire results from 84 experimental participants. But the display wasn’t a fish tank that you could fit in your living room—it was a large exhibit at the National Marine Aquarium in Plymouth, United Kingdom.
Sitting and looking at the display led to significant reductions in blood pressure and heart rate. “Most of these gains occurred within the first five minutes,” the authors write. (The results are not due simply to sitting, they say, as experimental participants had a rest period before a curtain was opened to reveal the display.)
If an environment is rich, fascinating, in line with the person’s likes, and involves being away from the daily routine, then it will be restorative.
The researchers were able to take advantage of a new marine life display being created at the museum. They took measurements when the display was "empty," about half full, and fully stocked. The empty display contained artificial seaweed and corals, and was full of sea water that needed time to settle, but no fish. When half full, the tank contained 60 fish (of six species) and 14 crustaceans (of two species). Fully stocked, there were 138 fish (19 species) and 13 crustaceans (of three species).
Not surprisingly, ordinary visitors to the museum spent longer in front of the display when it was partially or fully stocked. There was a lot of variation, with the average time being about four minutes, but some people spent up to 20 minutes looking at it. More than 100 members of the public were observed, with a sign at the entrance informing them a study was taking place.
Experimental participants were recruited to come to the museum at one of the three time points. “Participants in all three conditions found 10 minutes in front of the exhibit was an enjoyable and interesting experience that made them feel better,” the researchers write. Even when the exhibit was empty, participants said they would be willing to sit in front of it for another seven and a half minutes. But they said they were willing to observe it for significantly longer—11 and a half minutes—when it was partially or fully stocked.
The partially and fully stocked conditions led to bigger improvements in mood, enjoyment, and how interesting it was compared to the empty display. All three stages of the exhibit also led to decreases in heart rate and blood pressure. Heart rate dropped more when the tank was full or partially full compared to when it was empty.
"In general, as duration of exposure increased people became both more positive and calmer, but as biota [marine life] levels increased, people became more positive but relatively less calm," the researchers write. "This latter finding is concordant with the notion that greater levels of biota are associated with more interest and fascination." In other words, the more fish there were in the tank, the more interesting it was to watch.
There are several theories that might explain these results. One is the idea that people have an innate tendency to like nature (the biophilia hypothesis). Another theory is that spending time in nature is restorative and can improve feelings of stress and fatigue from concentration (attention restoration theory). If an environment is rich, fascinating, in line with the person’s likes, and involves being away from the daily routine, then it will be restorative.
Previous studies of the effects of aquaria in health-care settings have had mixed results. More research is needed to find out if an aquarium of the type people keep fish in at home would have similar effects. But this study found that watching the exhibit for just a short time had psychological benefits.