Incidental and intentional visual memory: What memories are and are not affected by encoding tasks?

Abstract

Prior research into the impact of encoding tasks on visual memory (Castelhano & Henderson, 2005) indicated that incidental and intentional encoding tasks led to similar memory performance. The current study investigated whether different encoding tasks impacted visual memories equally for all types of objects in a conjunction search (e.g., targets, colour distractors, object category distractors, or distractors unrelated to the target). In sequences of pictures, participants searched for prespecified targets (e.g., green apple; Experiment 1), memorized all objects (Experiment 2), searched for specified targets while memorizing all objects (Experiment 3), searched for postidentified targets (Experiment 4), or memorized all objects with one object prespecified (Experiment 5). Encoding task significantly improved visual memory for targets and led to worse memory for unrelated distractors, but did not influence visual memory of distractors that were related to the target's colour or object category. The differential influence of encoding task indicates that the relative importance of the object both positively and negatively influences the memory retained.

Keywords:

• Visual memory
• Incidental v. intentional encoding
• Visual search

Acknowledgements

I want to thank Emily Watts, Josh Liddel, Jordan Griffin, Chareika Fox, Michael Keeton, and Liberty Wise for their help with data collection and Camilla Williams for her help in editing the manuscript. Portions of this research were presented at the 50th annual meeting of the Psychonomic Society (2009) in Boston, MA.

Notes

¹A subset of the object categories from Williams et al. (2005) were replaced (axe, hammer, knife handle, pen, pliers, scissors, and screwdriver) because the colour for these objects was limited to only a portion of the object (e.g., red axe handle), making them more difficult to describe as a search target than the remaining objects. The replacement objects (bottle, stand mixer, wristwatch, vase, tape dispenser, toaster, and book, respectively) matched the original objects on colours.

²One could argue that related distractor memory was improved compared to unrelated distractor memory in Experiment 5 because the colour-category label would benefit all objects that shared a feature of the label. If the knowledge that a particular colour and category would be presented was sufficient to improve memory, the related distractors in Experiment 5 should have been remembered better than those of the experiments where no label was given prior to the sequence (Experiments 2 and 4). However, memory performance for the category distractors in Experiment 5 was numerically worse than the same objects in Experiments 2 and 4, t(70)=–1.68, p=.098, and colour distractor memory was only marginally better than the Experiments 2 and 4, t(70)=1.84, p=.07. Thus, the knowledge that an object will appear that shares a colour or category does not necessarily improve memory for a related object.