Is colour as important as shape for remembering objects?
Practising memory for some objects made people forget other objects that shared only their colour just as much as objects that shared only their shape, suggesting colour is a full-strength memory cue.
Source
The relative contribution of shape and colour to object memory
Study at a glance
- Design
- Human experiment — Two lab experiments using a recognition-practice (retrieval-induced forgetting) paradigm with a practice group and a no-practice control group; Experiment 1 used familiar objects, Experiment 2 novel objects.
- N
- 40 university students per experiment (20 practice group, 20 control group); separate samples in Experiments 1 and 2.
- Population
- Undergraduate students at Swansea University with normal colour vision.
- Outcome
- Recognition memory sensitivity (A') at test for unpractised objects sharing shape, colour, both or neither with practised objects, compared with baseline items and a control group.
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What they did
Students studied 40 target objects for 5 seconds each, then a practice group did three rounds of old-new recognition on a small subset while a control group did filler tasks. Unpractised objects were built to share only shape, only colour, both, or neither with the practised ones. Experiment 1 used everyday objects such as chairs and lamps; Experiment 2 used novel made-up objects that could all be told apart by shape alone, so colour was irrelevant to the task.
What they found
In both experiments, objects sharing only colour and objects sharing only shape with practised items were recognised less well, a pattern called retrieval-induced forgetting, and the two effects were of similar size (in Experiment 1, d = .56 for shape-only items). Objects sharing both features showed no forgetting in Experiment 1, where they were nearly identical to practised items, but did in Experiment 2, where their parts were rearranged. Objects sharing neither feature were not forgotten, and practice did not measurably boost memory for the practised objects themselves.
The limits
What it doesn't show
Each group had only 20 students, all from one university, and several key interactions were only marginal, so effect-size estimates are imprecise. The conclusion that colour and shape contribute 'equally' rests on finding similar forgetting effects rather than a formal test of equivalence. The paradigm infers memory contents indirectly from forgetting, and the authors note a non-inhibitory blocking account could in principle explain some of the pattern; the task used pictures on a screen, not real objects or longer delays.
Key terms
- Retrieval-induced forgetting (RIF)
- Practising retrieval of some memories impairs later memory for related but unpractised items that competed with them during practice.
- Recognition practice
- A version of retrieval practice in which people repeatedly judge whether items are old or new rather than recalling them.
- Rp+, Rp– and Nrp items
- Practised items, unpractised items related to practised ones, and unpractised items from unpractised categories that serve as the baseline.
- A' (A-prime)
- A non-parametric measure of recognition sensitivity that combines hits and false alarms; higher means better discrimination of old from new.
- Encoding specificity
- The principle that memory is best when the cues present at retrieval match those present when the item was learned.
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Quiz yourself
In this study, what showed that colour is used to retrieve objects from memory?
Common questions
Why use forgetting to study what is stored in memory?
If a feature like colour is part of an object's memory, other objects with that colour compete when you practise retrieving it and later suffer forgetting; so forgetting is an indirect sign that the feature is used to index memories, without asking people to attend to it.
Why did the 'both features' objects escape forgetting in Experiment 1?
They were almost identical to the practised objects, so practice probably primed them instead of suppressing them; when similarity was reduced in Experiment 2, they were forgotten as predicted by Anderson's feature-overlap model.
Doesn't shape matter more for recognising objects?
For naming and categorising, shape usually dominates, but this study suggests that for retrieving specific episodes from memory colour is used about as strongly as shape, even when shape alone would be enough.
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