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Effect of circadian rhythms on retrieval-induced forgetting

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This study investigated the effects of natural circadian rhythms on retrieval-induced forgetting (RIF; Anderson et al. in J Exp Psychol Learn Mem Cogn 20:1063–1087, 1994). Individuals tested at optimal times (i.e., morning persons tested in the morning and evening persons tested in the evening) showed a significantly greater RIF effect than individuals tested at non-optimal times (i.e., morning persons tested in the evening and evening persons tested in the morning). Thus, the limited quantity of resources available to allocate in the inhibitory activity during non-optimal times produced a significant decrement in RIF. These findings are compatible with the inhibitory account of RIF and with the notion of a resource-demanding process underlying this memory phenomenon.

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Fig. 1


  1. We paid particular attention in selecting anagrams whose solutions were far from interfering with the experimental categories and items. None of the solutions of the anagrams were close to creating interference with the recall of experimental categories and items.

  2. Before breaking the results down by two separate 2 × 2 ANOVAs, we conducted a 2 × 2 × 2 mixed-model ANOVA with item strength (strong vs. weak items) and item type (Nrp and Rp− items) as repeated measures factors and synchrony (optimal times vs. non-optimal times) as a between subject factor. This analysis revealed a significant main effect of item strength, F (1, 50) = 11.80, p < .001, 2 = .19, and a significant main effect of item type, F (1, 50) = 11.04, p < .001, 2 = .18. Furthermore, the interaction between item type and synchrony and the interaction between item type and item strength were both significant, F (1, 50) = 7.52, p < .01, 2 = .13 and F (1, 50) = 10.15, p < .01, 2 = .17, respectively. Finally, the three-way interaction was not significant, F (1, 50) = 1.32, p > .2, 2 = .03. Possibly, this last result is due to a general lack of statistical power. However, in order to better address whether synchrony differently affected RIF for strong and weak categories, we conducted two separate ANOVAs, one for high taxonomic frequency and one for low taxonomic frequency exemplars (see Anderson et al. 1994, for similar procedure).


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Correspondence to Gennaro Pica.



Categories and exemplars used in the retrieval-practice task sorted by category composition (high taxonomic frequency and low taxonomic frequency exemplars). The Italian translation of the exemplars is provided in parentheses.




High taxonomic frequency


Cat (Gatto), Giraffe (Giraffa), Cow (Mucca), Horse (Cavallo), Tiger (Tigre), Lion (Leone)


Cannon (Cannone), Sword (Spada), Gun (Pistola), Bomb (Bomba), Rifle (Fucile), Knife (Coltello)


Aluminium (Aluminio), Silver (Argento), Steel (Acciaio), Zinc (Zinco), Lead (Piombo), Iron (Ferro)


Icecream (Gelato), Tiramisu’, Cake (torta), Pudding (budino), Tart (Crostata), Pastry (Pastiera)

Low taxonomic frequency


Hydroplane (Aliscafo), Mini-van (Pilmino), Raft (Zattera), Airship (Dirigibile), Lambretta, Inflatable (Gommone)


Rally, Motocross, Snowboard, Chess (Scacchi), Wrestling, Minigolf


Chestnut Brown (Castano), Vermilion (Vermiglio), Magenta, Amber (Ambra), Emerald (Smeraldo), Ruby (Rubino)


Holly (Agrifoglio), Ironwood (Carpino), Conifer (Conifere), Ebony (Ebano), Tree-fern (Felce), Silver-wattle (Mimosa)

Control: high taxonomic frequency


Worker (Operaio), Teacher (Insegnante), Lawyer (Avvocato), Doctor (Medico), Professor (Professore), Employee (Impiegato)

Control: low taxonomic frequency


Flipper, Colorforms (Formine), Kite (Aquilone), Puppet (Burattini), Domino, Trading card (Figurine)

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Pica, G., Pierro, A. & Kruglanski, A.W. Effect of circadian rhythms on retrieval-induced forgetting. Cogn Process 15, 29–38 (2014).

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