Do Horses See Colour?

I used to work in a University Animal Behaviour laboratory. We generally did “operant” experiments where you teach the animal to make a response for food – peck a button, nose a lever, press a lever with your paw depending on what species of animal we were studying. Then set up rules and stimuli associated with the food delivery and you can get the animals to tell you about their world.

The boss came to me one day, “We have a student who really wants to do her Masters thesis using horses.  It’s up to you, if you want to do it then we’ll say yes”.   Generally, most of the research we did was with hens and more lately possums.  They are small and inexpensive to attain and feed.  Did I want to have horses at work?… well YEAH!

As the research tech in charge of the day to day running of the lab I was in charge of sourcing animals and caring for them or setting up systems so others (students and part-time cleaners) could care for them as well as building equipment, programming computers, keeping records etc etc.  So now that would include horses 😊

So I started to plan the equipment… it would need back projecting colour slides, a feed delivery device of some sort and some levers for the horses make their choices.  After some initial construction of a stall type layout that would face into a garage area I brought my pony, “Red”, in to test it out.  Red’s primary job was to be paddock mate for a retired racehorse I had – a famous one actually, he’d won the Melbourne Cup in 1976!  I’d been looking after him since his retirement around 1984.  But I had another horse at home so Red was able to come to work.  He was perfect for a test pony as he was quite nervous, “Get a grip Red” was a daily phrase, if I built equipment that Red was happy in, then chances were all horses would be ok.

Just as well Red was there, he was NOT happy with the way I initially had the stall set out.  I had to turn it around so the horses could go into the garage and turn into the stall facing out.  This made it more difficult to have the back projecting slides but Red was happier.  And if you think about the garage as being sort of like a cave then no horse is going to want to stand facing inwards, they will want to turn and face out.  We later discovered also that having a friend tied up next to the stall was a great help, so each horse took a turn at being subject or support horse each day.

Back projection was solved by getting the student’s mother to sew up a tent of black material.  With virtually no budget and not a whole lot of time the feeder ended up being automatic dispensing but not automatic filling.  So after each reward was triggered (positive food reinforcement) the student had to reach up, reset the little food hopper and put the next feed in there.  Basically she did a whole lot of squats each day, who needs gym membership!

The task the horses were going to do was relatively straight forward.  There were two levers for them to press, each in front of a small screen.  Each screen would show a slide, one a colour one grey.  The correct response was to press the lever in front of the coloured slide.  Every correct would be signalled by a short beep, from time to time there would also be a small amount of food dropped into the bowl between the levers.  Which screen the colour  was projected on would vary randomly for each trial.

Interestingly you cannot give food for every correct response.  If you do then the horse can just press one lever for every trial and get fed half the time, that is every time the correct colour is on that side.  Much easier than having to think!  So we set up a rule that is “the next feed will be for a correct left/right trial”, that way in order to get fed the horses had to respond on both levers, if you respond only on the left lever when the next feed is due on the right you will never receive any food no matter if you get the trial correct or not.  On all trials the horse got correct there was also a short beep to signal correct even if not fed.  If the horse pressed the lever in front of the grey screen then there was no beep or food.

One interesting thing we discovered early on in the initial training was that the horses found pressing the lever very easy and they were very enthusiastic.  We had just given a pony control of the food delivery!  Red was very happy.  The problem was that although we had set it up so that initially any lever press when the screens were both showing a coloured slide would get food, the horses would play with the lever the whole time, so the slides would show for only a fraction of a second.  We needed them to actually learn to look at the screens, they weren’t even going to notice them at all if they didn’t slow down the lever pressing!  So we set up a rule… not only did the screen need to be on for the lever press to be effective but there had to be no lever presses for three seconds before the screen would turn on.  This worked very well and got all horses looking at the screens as a signal that the lever would work.  

To ensure that the horse could not discriminate on any difference in brightness between the colour and grey slides there were three brightnesses of each colour, and each of those was paired with greys that were lighter, darker or the same brightness.  So for any trial the correct colour choice could be the same brightness as the grey screen or lighter or darker.

I wrote an article for horsetalk on the results of the study… follow this link to find out what we discovered!