How to do a meta‐analysis

Meta‐analysis is a statistical tool for estimating the mean and variance of underlying population effects from a collection of empirical studies addressing ostensibly the same research question. Meta‐analysis has become an increasing popular and valuable tool in psychological research, and major review articles typically employ these methods. This article describes the process of conducting meta‐analysis: selecting articles, developing inclusion criteria, calculating effect sizes, conducting the actual analysis (including information on how to do the analysis on popular computer packages such as IBM SPSS and R) and estimating the effects of publication bias. Guidance is also given on how to write up a meta‐analysis.     

Bitter avoidance in guinea pigs (Cavia porcellus) and mice (Mus musculus and Peromyscus leucopus)

Rejection of bitter substances is common in many species and may function to protect an animal from ingestion of bitter-tasting toxins. Since many plants are bitter, it has been proposed that high tolerance for bitterness would be adaptive for herbivores. Earlier studies conducted on herbivorous guinea pigs (Cavia porcellus) have been used to support this proposal. We tested guinea pigs with bitter plant secondary metabolites (salicin, caffeine, quinine hydrochloride) and bitter protein hydrolysates (two types of hydrolyzed casein, hydrolyzed soy) in a series of two-choice preference tests. For comparison, we tested two nonherbivorous mouse species (Mus musculus and Peromyscus leucopus). Guinea pigs did show weaker avoidance of quinine hydrochloride than did the mice, confirming predictions generated from earlier work. However, guinea pigs had similar responses to caffeine as did Peromyscus. Both of these species showed weaker avoidance responses than Mus to 10 mM caffeine. For salicin, guinea pigs were the only species to avoid it at 10 mM and their preference scores at this concentration were significantly lower than for the two mice species. Guinea pigs avoided all of the protein hydrolysates more strongly than the other species. Responses to the protein hydrolysates did not reflect the patterns observed with the simple bitter compounds, suggesting that other properties of these complex stimuli may be responsible for guinea pig avoidance of them. Our results suggest caution in accepting, without further empirical support, the premise that guinea pigs (and herbivores in general) have a generalized reduced bitter sensitivity.     

Temperature increases in preterm infants during massage therapy

Temperature was assessed in 72 preterm infants randomly assigned to a control or a massage therapy group. A greater increase in temperature was noted for preterm infants receiving massage therapy versus a control group, even though the incubator portholes remained open during the 15 min massage therapy session but not for the control group over an equivalent time period.     

Breastfeeding and antidepressants

Although a large literature supports the benefits of breastfeeding, this review suggests that breastfeeding is less common among postpartum depressed women, even though their infants benefit from the breastfeeding. Depressed mothers, in part, do not breastfeed because of their concern about potentially negative effects of antidepressants on their infants. Although sertraline (Zoloft) and paroxetine (Paxol) concentrations are not detectable in infants’ sera, fluoxetine (Prozac) and citalopram (Celexa) do have detectable levels. Unfortunately these findings are not definitive because they are based on very small sample, uncontrolled studies. As in the literature on prenatal antidepressant effects, the question still remains whether the antidepressants or the untreated depression itself has more negative effects on the infant. It is possible that the positive effects of breastfeeding may outweigh the positive effects of the antidepressants for both the mother and the infant. In addition, some alternative therapies may substitute or attenuate the effects of antidepressants, such as vagal stimulation or massage therapy, both therapies being noted to reduce depression. Further studies of this kind are needed to determine the optimal course of therapy for the benefit of the depressed, breastfeeding mother and the breastfed infant.     

Differential sucking by neonates of depressed versus non-depressed mothers

Forty-two neonates (M = 39-h old) of depressed and non-depressed mothers sucked on cold (50 °F) and warm (78 °F) nipples on alternating trials. Half the infants received the cold nipple on the first of the eight trials (20 s each) and the other half received the warm nipple first. Neonates of depressed mothers sucked twice as much as neonates of non-depressed mothers, suggesting arousal dysregulation, overactivity or greater hedonic behavior in the newborns of depressed mothers. Although the newborns did not show a preference for cold or warm nipples, a temperature order effect revealed that neonates who received the cold nipple on the first trial sucked significantly more on trials 2–8 than those who received the warm nipple on the first trial, suggesting that an initially cold nipple might elicit greater sucking. More research is needed on maternal mood effects and temperature of objects to determine how these factors affect neonatal sucking behaviors.     

Counselling strategies for bereaved people offered in primary care

The aim of this study was to identify strategies that general practice-based counsellors used when offering support to bereaved clients. Over the last decade, there has been a rapid growth in the provision of counselling services associated with British primary care services. A study was designed involving qualitative methods of data collection (semi-structured interviews) and analysis (a grounded theory approach). Counsellors were recruited from two cities in Southern Britain (Plymouth and Southampton). Twenty nine (76% response rate) counsellors agreed to participate (Southampton n = 15, Plymouth, n = 14). Semi-structured face-to-face audio-taped interviews elicited information about their perceptions of the appropriateness of general practitioner referrals, counselling strategies and models of bereavement. Analysis indicated that counsellors saw bereavement counselling within a broader agenda of work concerned with loss and relationship management. Many drew on eclectic approaches to bereavement counselling and specific strategies included: facilitating telling of the 'story' of the loss; engaging in active listening and valuing allowing people to talk; establishing a supportive relationship; and enabling the bereaved person to deal with unfinished business and to say 'goodbye'. Counsellors drew on implicit stage/phase models of grief that assumed levels of distress reduced over time. The value of these strategies requires more exploration.     

Epistemology without metaphysics

The paper outlines a view of normativity that combines elements of relativism and expressivism, and applies it to normative concepts in epistemology. The result is a kind of epistemological anti-realism, which denies that epistemic norms can be (in any straightforward sense) correct or incorrect; it does allow some to be better than others, but takes this to be goal-relative and is skeptical of the existence of best norms. It discusses the circularity that arises from the fact that we need to use epistemic norms to gather the facts with which to evaluate epistemic norms; relatedly, it discusses how epistemic norms can rationally evolve. It concludes with some discussion of the impact of this view on “ground level” epistemology.

The relation of self-esteem variability to emotion variability, mood, personality traits, and depressive tendencies

The relation of self-esteem variability to personality, mood, and behavior was investigated. Self-esteem variability was measured by calculating the standard deviation of self-ratings made during a week of experience-sampling. Participants high in self-esteem variability were self-conscious, socially anxious, and avoidant of social contexts. Self-esteem variability was partially independent of the conceptually similar trait of affect-intensity. The contributions of the study to work on self-esteem stability are discussed.     

Preventative Behavioral Parent Training: A Preliminary Investigation of Strategies for Preventing At-Risk Children From Developing Later Conduct Problems

Children exhibiting conduct problems comprise the largest source of referrals to children's mental health services. The treatment for conduct problems that possesses the greatest amount of empirical support is behavioral parent training. Unfortunately, a cogent approach to the identification of risk factors and prevention of chronic conduct problem display has not been developed. This project was an initial longitudinal assessment examining the merits of preventative behavioral parent training as a primary prevention strategy for at-risk children. Results demonstrated that prevention participants were engaging in normative rates of disruptive behaviors at 6-month follow-up, whereas comparison children showed a behavioral decline over time.