Long-term memory
Is colour as important as shape for remembering objects?
Open access · cc by · source: Europe PMC
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.
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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Key findings
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.
Methodology
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.
Limitations
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.
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