Dr Robert W Stackman, Jr – Dr Sarah J Cohen | Of Mice and Matching: When Rodents Show They Can Match Pictures to Objects

Researchers at Florida Atlantic University have discovered that mice possess a sophisticated cognitive ability previously thought to be limited to primates and certain bird species – they can recognise real objects after only seeing pictures of them. This breakthrough finding not only challenges our understanding of rodent intelligence but also opens new possibilities for studying human memory and cognition.

Testing Mice Visual Recognition

Have you ever picked up a physical product and recognised it immediately because you’d seen it advertised in a magazine or online? This ability to match a real object with a picture seen previously – a skill known as picture-object equivalence – is something humans often take for granted. For years, scientists believed this cognitive skill was limited to humans, other primates, and a few bird species. Now, groundbreaking research reveals that mice also possess this ability, challenging long-held assumptions about rodent intelligence and visual processing capabilities.

The implications reach beyond simply understanding mouse cognition. Since mice are widely used in research on human brain disorders and diseases, confirming that they share this fundamental cognitive ability with humans makes them even more valuable as model organisms for investigating human memory and learning.

A New Way to Test Mouse Memory

Drs Robert Stackman and Sarah Cohen at Florida Atlantic University set out to investigate whether mice could demonstrate picture-object equivalence through a series of innovative experiments. Traditional methods for studying animal memory usually involve having the animals directly interact with physical objects. However, Drs Stackman and Cohen’s team modified these tests so that mice were first shown photographs of objects, and then later presented with real, three-dimensional (3D) versions to see if they could make the connection.

‘There was a prevailing view that this kind of representational insight – understanding that a 2D picture corresponds to a 3D object – might be beyond rodents’ capabilities,’ explains Dr Cohen. ‘But we found that mice can spontaneously make this connection, provided they have enough time to carefully view and encode the picture in their memory.’

How Do You Test If a Mouse Recognises Something?

The research team leveraged the natural curiosity of mice and their tendency to spend more time investigating novel items than familiar ones. In their experiments, mice were first shown photographs of objects during a ‘sample session’. Twenty-four hours later, in the ‘test session’, the mice were presented with both the actual 3D object from the photograph and a novel 3D object they had never encountered.

If the mice could match the real object to the picture they had seen earlier, they would treat it as ‘familiar’ and focus their attention on the new object instead. This is precisely what the researchers observed – the mice consistently spent more time exploring the novel objects rather than those they had previously seen in picture form.

Ruling Out Simple Explanations

Naturally, sceptics might argue that the mice were simply responding to basic visual features, such as colour or shape, rather than truly understanding the connection between pictures and objects. To address these concerns, Drs Stackman and Cohen’s team conducted several additional experiments to rule out these simpler explanations.

They tested whether mice could still match pictures to objects when the objects were rotated to show different angles, when the pictures were black-and-white silhouettes, when the objects shared similar sizes and colours but differed in shape, and when the pictures displayed only outlines of the objects.

In all cases, the mice successfully demonstrated picture-object equivalence, indicating that they weren’t merely responding to basic visual cues but were, in fact, making the cognitive leap between 2D representations and 3D reality.

The Hippocampus as Key to Picture Recognition

The research team also investigated which parts of the mouse brain were involved in this picture-object matching ability. They discovered that temporarily inactivating a brain region called the hippocampus – known to be essential for memory – prevented the mice from matching pictures to objects.

Dr Robert Stackman explains, ‘This finding suggests that the hippocampus plays a crucial role in storing and processing visual memories in a way that allows mice to later recognise real objects they’ve only seen in pictures’. This insight parallels what we know about visual memory processing in humans, further supporting the use of mice as model organisms for studying human cognitive processes.

Implications for Research and Understanding

This discovery has significant implications for both fundamental research and our understanding of animal cognition. First, it shows that mice possess more sophisticated visual processing abilities than previously thought, prompting an assessment of their potential cognitive capabilities.

More practically, this finding strengthens the case for using mice to study aspects of human memory and visual processing. Many neurological and psychiatric conditions affect these cognitive processes, and having a reliable animal model that shares fundamental cognitive abilities with humans is invaluable for advancing research.

The research team is now exploring how this ability develops in mice and whether it might be impaired in mouse models of human cognitive disorders.

New Horizons for the Study of Human Cognitive Disorders

The discovery that mice can match pictures to objects opens exciting new avenues for research. Drs Stackman and Cohen and their colleagues are now developing more sophisticated tests to determine the limits of mouse recognition abilities. They are also investigating how this capability might be affected in mouse models of conditions like Alzheimer’s disease or schizophrenia, which often impact visual processing and memory.

‘This finding really changes how we think about mouse cognition’, says Dr Cohen. ‘It suggests that mice process visual information in ways more similar to humans than we previously thought, making them even more valuable for studying human cognitive disorders.’

The research also raises intriguing questions about the evolution of visual processing and recognition abilities across different species. If mice can perform this complex cognitive task, what other capabilities might they – and other animals – possess that we have yet to discover? As we continue to unravel the intricacies of animal cognition, this research reminds us not to underestimate the capabilities of other species. Sometimes, they might be more like us than we realise.