Research Note: Evaluation of the incidence of white striping and underlying myopathic abnormalities affected by fast weight gain in commercially fed broiler chickens.

Significant improvements in genetics, nutrition, and food efficiency have had a great impact on the rapid growth of broilers, notably with increases in muscle mass. However, with rapid growth, the broiler industry has been negatively impacted by the increased incidence of myopathies, including white striping. White striping affects the pectoralis major muscle of broilers, particularly the larger breasts of rapidly growing modern commercial broiler lines. In this study, we documented the growth process of commercial broiler chickens from hatching to market weight at 6 wk. Gross pathology and histopathology analyses were performed on pectoralis major muscle collected weekly from birds culled from 1 to 6 wk. The severity of both gross and histologic pathologies in the breast muscle increased over time. White striping was initially observed at week 2, with a rise in the incidence and severity through the sixth week. Mild histopathology was noted in week 2, characterized by macrophage infiltration and limited phagocytosis of the muscle. Muscle condition deteriorated with age and weight gain, with more prevalent macrophages, phagocytosis, and interstitial fibroblasts. By week 5 and 6, there was severe myopathy including regions of obliterated muscle tissue. Linear regression models show a positive correlation between white striping, gross pathology, and histopathology relative to weight and age.

Older and younger adults' interactions with friends and strangers in an iterated prisoner's dilemma.

This study examined age-related differences in behavioral reactions to interpersonal conflict within an iterated prisoner's dilemma (PD). Participants completed an iterated PD game alone and with a partner, either a stranger or a friend who accompanied them to the session. The partner, however, was actually a program that occasionally behaved selfishly or always reciprocated. Afterwards, participants formed trait impressions of their partner's morality and competence. Participants cooperated more with friends than strangers and more with reciprocating partners than selfish ones. Older adults cooperated more with selfish partners and offered more favorable impressions than did younger adults. Overall, perceived partner trait morality was positively associated with cooperative behavior. Relative to younger adults, older adults were more passive during conflict but grew less so as selfishness continued. This passivity co-occurred with more favorable partner impressions and better objective performance, suggesting a degree of calibration not shown by younger adults.

Peripheral threat detection in facial expressions by younger and older adults.

Everyday threat detection includes recognizing threat cues in facial expressions found in our peripheral visual field. The current study examined age differences in the detection of emotion in low and high intensity angry and fearful facial expressions presented in younger and older adults' parafoveal (±5°) and peripheral visual field (±10°, ±15°). For both age groups, detection performance was better for higher than for lower intensity stimuli, and detection performance declined with greater peripheral distance. Although younger and older adults displayed a similar pattern of findings for angry facial expressions, younger adults appeared to be more sensitive to lower intensity fearful expressions across all viewing positions. These findings demonstrate that, although threat detection may be partly maintained into older age, neurophysiological changes may accompany aging that selectively reduce older adults' sensitivity to peripheral facial cues of fear.

The impact of emotional faces on younger and older adults' attentional blink.

The attentional blink (AB) is the impaired ability to detect a second target (T2) when it follows shortly after the first (T1) among distractors in a rapid serial visual presentation (RSVP). Given questions about the automaticity of age differences in emotion processing, the current study examined whether emotion cues differentially impact the AB elicited in older and younger adults. Twenty-two younger (18-22 years) and 22 older adult participants (62-78 years) reported on the emotional content of target face stimulus pairs embedded in a RSVP of scrambled-face distractor images. Target pairs included photo-realistic faces of angry, happy, and neutral expressions. The order of emotional and neutral stimuli as T1 or T2 and the degree of temporal separation within the RSVP systematically varied. Target detection accuracy was used to operationalise the AB. Although older adults displayed a larger AB than younger adults, no age differences emerged in the impact of emotion on the AB. Angry T1 faces increased the AB of both age groups. Neither emotional T2 attenuated the AB. Negative facial expressions held the attention of younger and older adults in a comparable manner, exacerbating the AB and supporting a negativity bias instead of a positivity effect in older adults.

Age-related differences in emotion matching are limited to low intensity expressions.

Multi-label tasks confound age differences in perceptual and cognitive processes. We examined age differences in emotion perception with a technique that did not require verbal labels. Participants matched the emotion expressed by a target to two comparison stimuli, one neutral and one emotional. Angry, disgusted, fearful, happy, and sad facial expressions of varying intensity were used. Although older adults took longer to respond than younger adults, younger adults only outmatched older adults for the lowest intensity disgust and fear expressions. Some participants also completed an identity matching task in which target stimuli were matched on personal identity instead of emotion. Although irrelevant to the judgment, expressed emotion still created interference. All participants were less accurate when the apparent difference in expressive intensity of the matched stimuli was large, suggesting that salient emotion cues increased difficulty of identity matching. Age differences in emotion perception were limited to very low intensity expressions.

Age-related differences in event-related potentials for early visual processing of emotional faces.

With advancing age, processing resources are shifted away from negative emotional stimuli and toward positive ones. Here, we explored this 'positivity effect' using event-related potentials (ERPs). Participants identified the presence or absence of a visual probe that appeared over photographs of emotional faces. The ERPs elicited by the onsets of angry, sad, happy and neutral faces were recorded. We examined the frontocentral emotional positivity (FcEP), which is defined as a positive deflection in the waveforms elicited by emotional expressions relative to neutral faces early on in the time course of the ERP. The FcEP is thought to reflect enhanced early processing of emotional expressions. The results show that within the first 130 ms young adults show an FcEP to negative emotional expressions, whereas older adults show an FcEP to positive emotional expressions. These findings provide additional evidence that the age-related positivity effect in emotion processing can be traced to automatic processes that are evident very early in the processing of emotional facial expressions.

The visual discrimination of negative facial expressions by younger and older adults.

Previous research has demonstrated that older adults are not as accurate as younger adults at perceiving negative emotions in facial expressions. These studies rely on emotion recognition tasks that involve choosing between many alternatives, creating the possibility that age differences emerge for cognitive rather than perceptual reasons. In the present study, an emotion discrimination task was used to investigate younger and older adults' ability to visually discriminate between negative emotional facial expressions (anger, sadness, fear, and disgust) at low (40%) and high (80%) expressive intensity. Participants completed trials blocked by pairs of emotions. Discrimination ability was quantified from the participants' responses using signal detection measures. In general, the results indicated that older adults had more difficulty discriminating between low intensity expressions of negative emotions than did younger adults. However, younger and older adults did not differ when discriminating between anger and sadness. These findings demonstrate that age differences in visual emotion discrimination emerge when signal detection measures are used but that these differences are not uniform and occur only in specific contexts.

If only I had taken my usual route : age-related differences in counter-factual thinking.

Previous research suggests that young adults can shift between rational and experiential modes of thinking when forming social judgments. The present study examines whether older adults demonstrate this flexibility in thinking. Young and older adults completed an If-only task adapted from Epstein, Lipson, and Huh's (1992 , Journal of Personality and Social Psychology, 62, 328) examination of individuals' ability to adopt rational or experiential modes of thought while making a judgment about characters who experience a negative event that could have been avoided. Consistent with our expectations for their judgments of the characters, young adults shifted between experiential and rational modes of thought when instructed to do so. Conversely, regardless of the mode of thought being used or the order with which they adopted the different modes of thought (i.e., shifting from experiential to rational in Study 1 and from rational to experiential in Study 2), older adults consistently offered judgments and justifications that reflected a preference for experiential-based thought.

Everyday problem solving across the adult life span: solution diversity and efficacy.

Everyday problem solving involves examining the solutions that individuals generate when faced with problems that take place in their everyday experiences. Problems can range from medication adherence and meal preparation to disagreeing with a physician over a recommended medical procedure or compromising with extended family members over where to host Thanksgiving dinner. Across the life span, research has demonstrated divergent patterns of change in performance based on the type of everyday problems used as well as based on the way that problem-solving efficacy is operationally defined. Advancing age is associated with worsening performance when tasks involve single-solution or fluency-based definitions of effectiveness. However, when efficacy is defined in terms of the diversity of strategies used, as well as by the social and emotional impact of solution choice on the individual, performance is remarkably stable and sometimes even improves in the latter half of life. This article discusses how both of these approaches to everyday problem solving inform research on the influence that aging has on everyday functioning.

Anger management: age differences in emotional modulation of visual processing.

Although positive and negative images enhance the visual processing of young adults, recent work suggests that a life-span shift in emotion processing goals may lead older adults to avoid negative images. To examine this tendency for older adults to regulate their intake of negative emotional information, the current study investigated age-related differences in the perceptual boost received by probes appearing over facial expressions of emotion. Visually-evoked event-related potentials were recorded from the scalp over cortical regions associated with visual processing as a probe appeared over facial expressions depicting anger, sadness, happiness, or no emotion. The activity of the visual system in response to each probe was operationalized in terms of the P1 component of the event-related potentials evoked by the probe. For young adults, the visual system was more active (i.e., greater P1 amplitude) when the probes appeared over any of the emotional facial expressions. However, for older adults, the visual system displayed reduced activity when the probe appeared over angry facial expressions.

Age differences in everyday problem-solving effectiveness: older adults select more effective strategies for interpersonal problems.

Using the Everyday Problem Solving Inventory of Cornelius and Caspi, we examined differences in problem-solving strategy endorsement and effectiveness in two domains of everyday functioning (instrumental or interpersonal, and a mixture of the two domains) and for four strategies (avoidance-denial, passive dependence, planful problem solving, and cognitive analysis). Consistent with past research, our research showed that older adults were more problem focused than young adults in their approach to solving instrumental problems, whereas older adults selected more avoidant-denial strategies than young adults when solving interpersonal problems. Overall, older adults were also more effective than young adults when solving everyday problems, in particular for interpersonal problems.

The differential effects of mood on age differences in the correspondence bias.

The present study found that age-related differences in the correspondence bias were differentially influenced by induced mood. Young and older adults completed an attitude-attribution task after having been induced to experience a positive, neutral, or negative mood. Although negative moods intensified age-related differences in the correspondence bias, young and older adults were equally susceptible to the correspondence bias when in a positive mood. In addition, induced mood differentially influenced the attributional confidence of young and older adults. Whereas negatively induced young adults were less confident than positively induced young adults in their attributions, negatively induced older adults were more confident than positively induced older adults in their attributions. Findings are discussed in terms of how positive and negative moods operate differently in motivating young and older adults' attributional judgments.