Peter E. Morris

Effect size estimates: Current use, calculations, and interpretation.

The Publication Manual of the American Psychological Association (American Psychological Association, 2001, American Psychological Association, 2010) calls for the reporting of effect sizes and their confidence intervals. Estimates of effect size are useful for determining the practical or theoretical importance of an effect, the relative contributions of factors, and the power of an analysis. We surveyed articles published in 2009 and 2010 in the Journal of Experimental Psychology: General, noting the statistical analyses reported and the associated reporting of effect size estimates. Effect sizes were reported for fewer than half of the analyses; no article reported a confidence interval for an effect size. The most often reported analysis was analysis of variance, and almost half of these reports were not accompanied by effect sizes. Partial η2 was the most commonly reported effect size estimate for analysis of variance. For t tests, 2/3 of the articles did not report an associated effect size estimate; Cohens d was the most often reported. We provide a straightforward guide to understanding, selecting, calculating, and interpreting effect sizes for many types of data and to methods for calculating effect size confidence intervals and power analysis.

The relationship between self reports of imagery and spatial ability

A puzzling question arising from imagery research is why no relationship has been found between self-reports of imagery and performance on spatial tests thought to require the use of imagery. To investigate this, spatial ability, measured by performance on two spatial tests, was compared with performance on the Vividness of Visual Imagery Questionnaire (VVIQ; Marks, 1973) and a newly constructed imagery questionnaire. The choice of items and ratings for the new questionnaire was based on Kosslyns (1980, 1994) theories of the imagery system. Ratings on the new questionnaire consistently correlated significantly with performance on the spatial tests, whereas ratings from the VVIQ did not. The new ratings captured more of the imagery process than ratings of vividness alone, but the largest change depended upon the type of item imagined. Ratings of items of the same type as used on the spatial tests predicted performance on the spatial tests, whereas vividness ratings of items recalled or constructed from long-term memory did not. Participants can successfully introspect on several different properties of their images, and their ratings do predict performance on tasks thought to require imagery. The large effect of item type raises questions about the predictive value of existing models of the imagery system especially in relation to the role of phenomenological properties of our images.

Linking images and free recall

An examination of the literature on free recall with instructions to form mental images suggests that recall is facilitated only when the images which are formed link items together. In Experiments I and II subjects were instructed to form images which linked together three items in one image, or to form separate images to each item. Recall was facilitated for the linking imagery subjects, but the separate imagery subjects had no better recall that the controls. Experiment III demonstrated that there was no interference with subjective organization in the single image condition. Apparently, mental imagery improves free recall through strengthening of the association between items, and not by improving the distinctiveness, availability, or form of storage of the individual items.

Selective interference with the use of visual images in the symbolic distance paradigm.

Eight experiments investigated the effects of visual, spatial, auditory, and executive interference on the symbolic comparison of animal size and ferocity, semantic goodness of words, and numbers. Dynamic visual noise (DVN) and the reading of visually presented stimulus items were shown to selectively interfere with response times on the animal size comparison task, though the slope of the symbolic distance function remained unchanged. Increased change of DVN significantly increased interference, but interference was reduced by equiluminant DVN. Spatial tracking reduced the slope of the symbolic distance function in contrast to an executive task that only increased mean latency and errors for all comparisons. Results suggest that the generation of an image is necessary for size comparison, but neither imagery nor executive function is responsible for the frequently observed distance-time function.

Expanding retrieval practice: An effective aid to preschool children's learning.

The benefits of expanding retrieval practice for preschool children were explored in two experiments. In Experiment 1, three groups learned names for six plush toy pigs using expanding retrieval practice, a reward incentive, or a control condition. Reward did not significantly improve learning but retrieval practice doubled recall. In Experiment 2, three groups learned names to soft toys, comparing recall following massed elaborative study with either expanding retrieval practice or expanding re-presentation. Recall was tested after 1 minute, 1 day, and 2 days. A very large effect size (d = 1.9) indicated the very considerable benefit from expanding retrieval practice over the elaboration condition. Comparison with the re-presentation condition suggested that half of the benefit of expanding retrieval practice came from spaced scheduling and half from retrieval practice. Expanding retrieval practice provides an effective method to improve learning by young children.

A CORRELATIONAL STUDY OF VARIABLES RELATED TO IMAGERY

This is an exploratory correlational study of a number of variables relating to imagery. The EEG of each of 32 Ss was monitored during post-observation imaging to words varying in imagery (Paivio, Yuille, & Madigan, 1968). Ss then recalled the words and completed several questionnaires. The following significant correlations were obtained; (i) Paivios I-rating of words and experienced imaging (p < 0.01); (i) Experienced imaging during the task and alpha abundance (EEG) (p < 0.05); (iii) Betts Test of Vividness of Imagery (QMI) and Gordon Test of Visual Imagery Control (p < 0.01); (iv) Betts QMI and incidental recall of words (p < 0.05); (v) Gordon test score and incidental recall (p < 0.05); (vi) Betts QMI and extroversion (p < 0.01), and (vii) extroversion and alpha abundance (p < 0.01). Two correlations of interest which failed to reach significance were: (i) Paivios I-rating of words and alpha suppression, and (ii) Paivios I-rating of words and incidental recall. Both findings may be attributed to the effects of differential instruction to image.

Attractiveness, distinctiveness, and recognition of faces: Attractive faces can be typical or distinctive but are not better recognized

The debate surrounding the relationship between facial attractiveness and distinctiveness appears to arise from different definitions of distinctiveness. In our study unfamiliar faces were rated for attractiveness, age, and distinctiveness. Two measures of distinctiveness were used: ease of spotting the face in a crowd (traditional) and deviation from an average face (deviation). Recognition was not predicted by attractiveness. The traditional ratings produced a complex relationship with attractiveness, where unattractive faces were distinctive, but attractive faces were rated at all levels of distinctiveness. When the effects of age were partialled out, attractiveness no longer predicted traditional distinctiveness. However, deviation ratings produced a strong negative correlation with attractiveness, even when the effects of age were removed.

Facial distinctiveness: Its measurement, distribution and influence on immediate and delayed recognition

It is conventionally assumed that many faces are relatively typical and few are distinctive (e.g. Valentine, 1991), producing a highly skewed distribution. However, Burton and Vokey (1998) argue that the distribution will be normal, and our review of previous research suggested this is true. In three studies we explored the distributions using different techniques to estimate distinctiveness. Both traditional ratings and pairwise selection produced normal distributions. However, ratings emphasizing the degree of deviation from a typical face were skewed towards the distinctive end of the scale. The instructions given when distinctiveness is rated may not necessarily oppose typicality with distinctiveness: a face that is relatively typical might also stand out in a crowd because of some particular feature, familiarity or a host of other reasons. In our fourth study, recognition memory was predicted by all of the distinctiveness measures, with the relationship being stronger after a 5-week delay than in the immediate test.

The improved name game: Better use of expanding retrieval practice

Morris and Fritz (2000) demonstrated the effectiveness of the name game as a retrieval-practice based technique for learning the names of group members. We hypothesised that a reversed version of the name game would be even more effective. Performance was contrasted with a no-retrieval condition that mimicked the name game in every way except for the retrieval of the names, allowing an estimate of the specific contribution of retrieval practice. The benefit of a few refresher rounds of the game after 2 weeks was also examined. The reversed name game was superior to the original name game and the refresher rounds benefited all groups. The very considerable superiority of the name game over the no-retrieval condition demonstrated the magnitude of the benefit of expanding retrieval practice.

Chapter 22 Imagery and spatial ability: When introspective reports predict performance

Publisher Summary This chapter attempts to take an initial step in constructing an introspective measure of imagery ability based on present theories and findings on the structure of the imagery system; one that will be of practical use in investigating the role of imagery in cognition. Two factors were considered in the construction of the questionnaire: the items and dimensions rated. Five items were selected that were either the same as or very similar to the type of items used in the five spatial tests with which the questionnaire was to be compared. The presentation of these items was also in a similar style to that of the items on the spatial tests. A variety of ratings was made for each item imagined. These were of two kinds, ratings of the subjective ease of a hypothesized process and ratings of pictorial aspects of an image that could reflect underlying processes either on their own or by interaction with each other. Throughout the questionnaire, the type of transformation required was of a single type, image rotation.