In one experiment brain damaged monkeys were trapped in tiny perspex boxes for up to an hour at a time to count how many times they would rotate. They would also be injected with amphetamine which made them rotate faster. Many monkeys found this distressing and bewildering. They could be seen crying out, foaming at the mouth, twisting frantically and desperately trying to escape.

"It's good fun to get them to do different tasks & to set up different tasks."
Researcher

Many of the monkeys were trained (called 'shaping') to carry out a number of behavioural and cognitive tasks prior to being brain damaged. After the infliction of brain damage, the animals were then made to repeat the same tasks. Their performance before and after the infliction of brain damage was then assessed. The monkeys were coerced into performing these tasks with the use of water deprivation and food restrictions. Some monkeys were subjected to both regimes. A thirsty and/or hungry monkey will 'work' (the term used by the researchers) for a reward of marshmallows, syrup soaked bread or a flavoured milk drink.

Some of the monkeys suffered from a weak arm or side of their body following brain damage. Tests were devised that required them to use their weak/damaged arm to retrieve a food reward.

Water deprivation meant that some experimental monkeys were only allowed water for two out of every 24 hours. Although there was some intermittent respite, the deprivation could continue for the entire length of the experiment which could last for two and a half years.

Some monkeys were also deliberately kept hungry by having their food restricted (receiving no breakfast or given half rations) or being given the 'test diet' (a bland, unappealing diet of pellets and carrots, which the researchers themselves recognised as being unpalatable to marmosets) to make the animals more receptive to the treats given during testing.

An 'extra' forage mix was given to the monkeys on a Friday afternoon for the weekend. However, some researchers would even deprive their research monkeys of this so that they could either 'work' them over the weekend or keep them hungry for testing on the Monday.

Here, at Cambridge University, these highly sensitive monkeys lived a barren existence in small, bare cages. The use of food and water deprivation was an additional source of stress inflicted on them. Our investigator found that experimental animals on food restriction could become very distressed as other monkeys were fed in cages around them. Brain damaged monkeys were sometimes placed back on a deprivation diet within just a short time of having surgery. It was clear that the provision of food and water was done to suit the needs of the researchers, not those of the monkeys.

Training

The training or 'shaping' of the marmosets to perform tasks could take up to 12 weeks to complete prior to brain surgery. Training could involve both correct behaviour being rewarded and incorrect behaviour being punished. Instructions for some researchers to follow included:

• Chase monkey into test box
• Keep 'miserable' or 'angry' marmosets in test apparatus
• Bang on the shutter, bang on the window
• Punish bad habits such as grooming by making a loud bang every time he does something wrong
• Lower the shutter... if necessary onto their fingers
• Use food restrictions to make the marmosets more amenable to 'shaping'

Testing

The monkeys were made to perform a range of tests both before and following brain damage. The tests used would depend on what experiment the animal was being used in.

One research project involved training the monkey to respond to the 'correct' image on a touch screen. To do this, the animals were kept in a small perspex box and shut inside another enclosed box. Various images were flashed up on the screen in front of them. If they touched the correct one, they were rewarded with a drink of flavoured milk. Some of these animals had a telemetric probe stitched into their body to measure blood pressure and heart rate. A researcher admitted to the BUAV investigator that one test had frightened a monkey when she was presented with a variety of images to get a response: "The very first stimulus the animal saw that wasn't the white square was a picture of a tree... the animal went nuts and was at the front of the screen and turned around and the split second after it saw the tree it darted to the back of the box and just stayed there for about a minute and the blood pressure raised incredibly. It was just amazing."

"It was just frightened. It didn't know what was going on. So that was the most impressive thing we've seen with this animal."

The effects of another kind of post-operative brain damage were measured by testing the ability of the monkeys to carry out skilled tasks using their limbs. For example, some brain damage resulted in the monkeys having a weak arm or side of their body. The 'staircase' or 'valley' test required brain damaged monkeys to use their damaged/weak arm to retrieve, through a narrow opening, the marshmallow rewards placed on a plastic staircase before them.

A particularly disturbing part to one experiment involved monkeys being confined in an extremely small perspex box for up to one hour at a time to see how often they would rotate. The brain damage inflicted would cause the monkeys to turn and/or rotate their bodies to either the left or right. The monkeys would also be injected with drugs beforehand which caused them to either rotate at a faster rate or to rotate in the opposite direction. The monkeys clearly found this highly distressing and bewildering and could be seen crying out, twisting frantically, foaming at the mouth or desperately trying to escape.

In another test, brain damaged monkeys had sticky paper labels attached around their feet or hands to see how they would remove them. Others had sticky plaster wrapped around one arm, forcing them to use their weak arm to retrieve marshmallows from tubes.

See for yourself some of the actual secret footage as filmed by our investigator.

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