A scientist holding a rat.

The 3Hs Initiative

Housing, Handling and Habituation

Improving the lives of laboratory rodents one lab at a time

Framework Concept​

To focus on the lifetime experience of laboratory mice and rats and methods which increase their positive affective experiences and reduce cumulative suffering.​

Core Aims

1. To reduce the use of physical restraint which causes distress, induces a negative affective state and can have long term detrimental effects on welfare and scientific outcomes​

2. To improve housing of laboratory rodents to provide more natural environments whilst also enabling the practical requirements of scientific studies​

3. To develop habituation methods to facilitate more positive affective associations with the handler and mitigate the negative impacts of aversive procedures​

4. To evidence the welfare benefits which can be achieved using our objective measures of affective state

A Bit More About Us

The Psychopharmacology Research Group was established in Bristol in 2007 by Professor Emma Robinson. Our research focused on investigating cognitive and affective behaviours in the context of psychiatric disorders particularly mood disorders.

Recognising the limitations of conventional models of depression, we prioritised developing new ways to objectively quantify affective state in rats and mice. We now have the methods needed to understand, in an unbiased way and avoiding anthropomorphic interpretations, the affective state of laboratory rats and mice. Using these methods, we are learning more about the welfare consequences of the procedures we use as well as the impact of the animal’s day to day environment on their wellbeing. We also apply these methods to validate the welfare benefits which can be achieved through the application of the 3Hs.

With support from the National Centre for the 3Rs and BBSRC we have put together this CPD learning resource to disseminate our 3Hs initiative. We have also added some additional resources for those interested in knowing more about our methods to quantify affective state and other approaches we employ to improve the translational validity of our animal research.​

How to Use This Resource

Each of the 3Hs modules provides details of methods we have shown have a positive impact on animal welfare.

Divided into each of the 3Hs and with information relevant to rats and mice, you will find videos, photos that illustrate the different approaches, and validation data where available. This is an active research programme, and we will continue to update the content of the site. We have also added an additional resources section’ where details of our objective methods to quantify affective state and information relating to our other programme about the importance of dose in preclinical research as well as downloadable guidance documents will be provided.​

Watch our webinar

Check out our recent webinar covering the background and principles of the 3Hs Initiative.

The webinar features practical examples of refinements to the housing, handling, and habituation of rats and mice. We provide quantitative evidence of welfare benefits and insight into protocols used in research active laboratories.

Watch now


The standard laboratory caging systems for rats and mice are known to provide limited opportunities for natural behaviours but are seen as necessary to enable animals to be managed in a way which is compatible with scientific procedures and space constraints.

All animals need to be health checked and animals undergoing procedures need to be readily identified, handled and monitored. The challenge is how to achieve positive impacts on welfare by providing opportunities for natural behaviour while also being able to manage the animals in a way which meets the scientific objectives. In this section we discuss our approaches to environmental enrichment and the impact of different housing environments on affective state.​

Read more about housing


As prey species, rats and mice are naturally fearful of human handling but the strains used in the laboratory are much more docile than their wild counter-parts.

While they have been selectively bred for animals which accept handling and are not normally aggressive, their association with humans can be improved by using positive reinforcement and minimising the use of physical restraint. Physical restraint is potentially aversive and reducing its use or avoiding it all together has positive welfare benefits. In this section, we describe methods which can be used to reduce the distress rats and mice can experience during common procedures particularly in relation to the administration of substances.​

Read more about handling


When animals are gradually introduced to a procedure, they become accustomed to it and their behaviour changes.

We often refer to this as habituation and it can be used to prepare animals for handling and procedures and reduce the distress they experience. To properly habituate an animal, a graduated training protocol is used which takes the animal from its current state to accepting the procedure using small progressive steps which minimise any aversive experience and enhance the positive.  In this section we describe our standardised protocols to habituate rats or mice to handling and prepare animals for substance administration using palatable solutions. We also provide examples of how a similar approach can be used for more complex procedures such as working with methods involving head mounted devices.

Read more about habituation

Additional Resources

In this section you can find more information about selected procedures we use in our own research and for which we have developed refined methods and approaches to improve the translational validity of studies in animal models.

This includes habituation methods to support studies involving restraint which are essential to the scientific objectives and appropriate dosing for studies involving substance administration. We also provide more information about our affective bias methods used to quantify affective state.​

Browse our resources

CPD Quiz and Certificate

Take this short quiz and receive your CPD certificate.

Feedback is provided with each of the questions when you submit your answer. At the end of the quiz we will ask you to provide some general demographic information.

Take the quiz

If you would like to follow up on any of the content or discuss the methods described, contact us as the following: