Discussion

A central aim of Experiment 1 was to understand whether OAs have age-related emotion recognition deficits when the experiment has been specifically designed to reduce many of the methodological and possible effects of sample differences that are evident in previous research. By limiting these possible confounding effects the current results may be more confidently attributed to emotion recognition ability rather than potential confounding variables that make comparisons across the field difficult. A further aim of Experiment 1 was to use a non-emotion task to examine whether the ability to meet task demands could explain age-related differences in emotion recognition accuracy. Finally, a more fine-grained understanding of emotion

recognition development in older age was achieved by comparing this ability between YAs, younger-older adults, and older-older adults.

It was hypothesised that OAs would have lower emotion recognition accuracy from static faces than YAs. Furthermore, it was predicted that age-related differences would not be the same across all emotion types. Specifically, OAs would be less accurate than YAs for recognising some negative emotions (sad, fear, or anger), whereas accuracy for disgust or happy recognition would be at least maintained. In contrast it was predicted that YAs and OAs would have comparable accuracy on the non-emotion task. It was also expected that the breadth of age-related emotion

recognition deficits would increase with advancing older age. The hypotheses were partially supported. OAs and YAs were comparable overall in emotion recognition ability, which was not predicted. However, when specific emotions were considered the hypothesis was somewhat supported as OAs were less able than YAs to accurately recognise anger, also OAs and YAs did not significantly differ in accuracy for disgust and happy recognition. Furthermore, the number of significant findings regarding age- related recognition deficits for specific emotion types with advancing older age remained at one, as older-older adults were less able to recognise sadness than the younger age groups. Finally, as predicted OAs and YAs did not differ in their ability to make non-emotion judgements from faces; however, older-older adults were less able than YAs and younger-older adults to make non-emotion and emotion categorical judgements from facial expressions.

In the current study OAs and YAs did not differ in their overall emotion recognition ability. A few studies concur with this finding that emotion recognition accuracy is similar across the age groups (e.g., Phillips, MacLean, & Allen, 2002). However, this is in contrast to some evidence that overall emotion recognition accuracy in OAs is lower than YAs on tasks using static faces (e.g., Calder et al. 2003; Isaacowitz et al., 2007; Keightley et al., 2006; Krendl & Ambady, 2010). The disparity in results

between studies, however, may be related to the different pattern of emotion recognition ability across emotion types. For instance, in both Keightley et al. (2006) and Krendl and Ambady (2010) OAs, compared to YAs, either had similar or reduced recognition accuracy across emotion types resulting in an overall age-related deficit in emotion recognition accuracy. In contrast, the OAs in the current study had higher mean scores for disgust recognition and were marginally better at identifying neutral facial

expressions than YAs, although neither of these differences reached significance. These two specific emotion recognition advantages for OAs, compared to YAs, perhaps

balanced out the age-related emotion recognition deficit for anger recognition. As a result the overall emotion recognition accuracy did not significantly differ between OAs and YAs. Therefore, overall emotion recognition accuracy should be treated with caution as it may mask advantages as well as disadvantages for recognition ability across discrete emotion types in OAs compared to YAs.

Furthermore, the present findings demonstrate that, compared to YAs, OAs have reduced emotion recognition ability for anger. An age-related deficit for anger

recognition in OAs is consistent with some of the previous age-related emotion recognition research (Calder et al., 2003; Isaacowitz et al., 2007; Phillips, Maclean, & Allen, 2002; Sullivan and Ruffman, 2004a). The current findings suggest, therefore, that age-related emotion recognition deficits in OAs are limited to anger. Given the careful design of the emotion recognition task it is likely that these age-related impairments can be best explained in terms of emotion recognition ability in OAs. In contrast to the current findings there is evidence of broader age-related emotion recognition deficits in OAs across emotion types. For example, Keightley et al. (2006) reported that OAs had poorer accuracy than YAs for the recognition of two emotions, fear and sadness, whilst Krendl and Ambady (2010) reported that OAs were less able than YAs to recognise four emotions in faces (happy, sad, fear, and anger). The disparity in the breadth of age-related emotion recognition deficits in the literature may reflect sample and methodological differences (e.g., education, gender, stimuli, response time limits). Whilst it is not possible to state exactly which of these

differences may account for the discrepancies between studies regarding the breadth of emotion recognition deficits in older age, the age differences between the OA samples may provide a useful explanation. For example, the OA sample in the current study had a mean age of 70 years and a study by Suzuki, Hoshino, Shigemasu and Kawamura (2007) used OAs with a comparable mean age (69.7 years) found only one age-related

emotion recognition deficit in OAs (albeit sadness rather than anger). In contrast, the OAs in Krendl and Ambady had a mean age of 75.8 years and the authors reported that OAs were less able to recognise four emotion types than YAs. As such the breadth of age-related emotion recognition deficits in Krendl and Ambady may reflect the

advanced age of their OA sample compared to the age of the current OA sample. This argument is somewhat supported by the findings in the current study that older-older adults are less able than YAs to recognise faces overall, as well as sad faces,

demonstrating a general decline in emotion recognition ability with advanced older age. It is likely, therefore, that the advanced neurological and cognitive changes that

naturally occur with increasing older age (Resnick, Pham, Kraut, Zonderman, & Davatzikos, 2003) impairs the ability of older-older adults to recognise emotions

compared to younger-older adults. This possibility is investigated in more detail later in the discussion.

Despite the current findings of age-related impairments for recognition of anger in OAs, the deficits did not extend to fear recognition between OAs and YAs and this is in contrast to previous research (Calder et al., 2003; Keightley et al., 2006; Krendl & Ambady, 2010). Calder at al. (2003) used age groups that were matched for gender and verbal intelligence in a similar fashion to the current study. Yet Calder et al. reported an age-related deficit for fear recognition in OAs. However, Calder et al. included surprise in their experiment and as explained in Chapter 2 (Section 2.1.6) an age-related decline for recognition of fear may reflect confusions between fear and surprise. The absence of surprise in the current task avoided the possible fear-surprise confusion; hence, the current findings imply that OAs are as able as YAs to recognise fear. This would be a plausible explanation only if other studies that excluded surprise from the emotion recognition task also failed to report age-related deficits for fear recognition. However, Krendl and Ambady (2010) did not assess the recognition of surprise

nevertheless found an age-related deficit for fear recognition in OAs. However, Krendl and Ambady used images taken from the DANVA 2 (Nowicki & Duke, 1994) and, as explained in Section 3.3.1, tasks based on this dataset appear to produce more age- related deficits than tasks based on alternative datasets. Thus, age-related impairments in recognition for fear in OAs maybe attributed to the choice of the face database or the inclusion of surprise in the task. However, the current study is not compromised by these two methodological issues, thus the maintenance of fear is likely to reflect emotion recognition abilities in OAs.

Finally, regarding findings for the negative emotions, the present study reports higher mean accuracy for disgust in OAs than YAs. However, the p value (p = .048) was nonsignificant when multiple comparisons were accounted for. Research has reported superior effects for disgust recognition in OAs compared to YAs (Calder et al. 2003; Suzuki et al., 2007; Wong, Cronin-Golomb, & Neargarder, 2005). A trend for increased accuracy for recognising disgust in older age suggests that emotion

recognition ability does not decline with age across all emotions. Calder et al. (2003) and Williams et al. (2009) argue that superior disgust recognition in OAs is a

maintained ability rather than an increased ability in old age, as disgust recognition is still developing in YAs. In this manner, age-related differences in disgust recognition are a function of an underdeveloped ability to detect disgust in YAs compared to a matured ability for disgust recognition in OAs (Calder et al., 2003). It should be noted though that there is some evidence that disgust recognition ability is either lower in OAs than YAs (e.g., Isaacowitz et al., 2007) or, as is the case in the current study, similar between the age groups (MacPherson, Phillips, & Della Sala, 2002). Hence an advantage in disgust recognition in OAs than YAs is not consistent across studies. Regarding positive emotions OAs were as accurate as YAs when recognising happiness from static faces. This preservation of emotion recognition for positive

emotion with age, coupled with age-related deficits in OAs for recognising negative emotions, may reflect a positivity effect in OAs (Charles, Mather, & Carstensen, 2003). However, as previously discussed (see Chapter 1, Section 1.7.1.3) a higher ability for happy recognition than other emotion types may also be a function of the task as it is easier to detect a singular positive emotion from an array of negative emotions (Isaacowitz & Stanley, 2011). It is, therefore, difficult to disentangle the two explanations using the typical emotion recognition tasks format. However, to distinguish between the possible influences of positivity effect or task design on the pattern of emotion recognition ability in OAs across emotion types research needs to use tasks specifically designed to tease apart the two concepts. This issue will be addressed in Phase 2 of the current thesis.

Turning to the possibility that emotion recognition deficits may increase with advancing older age, current findings suggest that, compared to YAs and younger-older adults, older-older adults had a recognition deficit for sadness; younger-older adults did not have any specific age-related emotion recognition impairments compared to YAs. Interestingly despite the possible effects of progressive cognitive and neurological changes with older age (e.g., Wilson, 2002) the older-older adults in the current study were still as able as YAs and younger-older adults to recognise happiness, fear, anger, disgust, and neutral faces. Furthermore, it appears that younger-older adults in the current study are as able to recognise emotions as YAs and it is only with advancing age that emotion specific recognition differences between the age groups emerge. The current findings, therefore, suggest that the age of the OA sample needs to be considered when comparing results in the field.

Regarding age-related emotion recognition deficits in older-older adults, the current findings are similar to one study that used an older OA sample than those typically found in the area. Stanley and Isaacowitz (2015) used an OA sample with a

mean age of approximately 75 years and compared to YAs these OAs were less accurate at recognising sad and angry faces. This finding is largely in line with the current research, however, age-related impairments for recognising anger in the current study was limited to comparisons between the extreme age groups of YAs and OAs and was not replicated when the older age group was split. Thus the advantage of the current study is that it provides a more fine-grained understanding of the effects of advancing older age on emotion recognition ability than research that has only compared YAs and OAs.

To recap, the current findings indicate that OAs are as able as YAs to recognise happy, fear, sad, disgust, and neutral faces; however, OAs are less able to recognise anger from static faces. Furthermore, older-older adults were less able to recognise emotion from faces with particular difficulties for sad faces than YAs, whereas

younger-older adults do not appear to have any emotion recognition deficits compared to YAs. These findings are discussed in relation to cognitive and neurological

explanations of emotion recognition.

Cognitive aging may provide a possible explanation for the current findings. According to the processing speed hypothesis faster speeds of processing facilitate cognitive performance (Salthouse, 1991). It is feasible that OAs’ slower processing speed than YAs may reduce their ability to process and categorise emotion information. Indeed there is some evidence that processing speed may account for some of the age- related deficits in emotion recognition ability in OAs (Horning, Cornwall, & Davis, 2012). However, if processing speed was the only explanation of a decline in emotion recognition ability in OAs then it may be expected that OAs would be less able than YAs to recognise all emotion types, rather than the select deficits reported in this study. Further, fluid abilities have been associated with emotion recognition ability in OAs (e.g., Horning, Cornwall, & Davis, 2012) but other studies suggest fluid intelligence

does not account for age-related emotion recognition deficits (e.g., Keightley et al. 2006). In the current study OAs had similar levels of fluid intelligence as YAs, therefore, cognitive aging based on intelligence is unlikely to explain the reported age- related impairment of anger. However, the OAs in the current study may have reduced abilities compared to YAs in unmeasured cognitive skills such as working memory or executive function. In particular lower executive function has been related to lower recognition accuracy for anger (Krendl & Ambady, 2010). Given the omission of a measure of executive function in the current study and the age-related differences in processing speed, then cognitive aging cannot be confidently rejected as an explanation of the current findings.

Furthermore, cognitive aging may help to explain the age-related emotion recognition deficits observed in the older-older adults. The older-older adults in the current study had significantly lower levels of verbal intelligence, fluid intelligence, and general cognitive functioning than younger-older adults. It is, therefore, possible that the demise in cognitive abilities with advancing older age may result in reduced recognition ability for sadness in older-older adults compared to younger-older adults. Although of interest the current older-older adults had similar cognitive abilities to YAs, thus cognitive demise with age is unlikely to fully explain the apparent decline in

recognition ability for sadness between these two age groups.

The current emotion recognition findings are somewhat in line with a

neurological explanation of emotion recognition ability in OAs (e.g., Ruffman, Henry, Livingstone, & Phillips, 2008). For instance, an age-related deficit in recognising anger in OAs may result from a rapid decline in the orbitofrontal cortex (OFC) compared to other neural areas in older age (Raz et al., 1997), as it has been shown that the OFC is involved in the processing of angry facial expressions (e.g., Sprengelmeyer, Rausch, Eysel, & Przuntek, 1998). Further, the age-related deficit for sad recognition in older-

older adults compared to YAs and younger-older adults may reflect an age-related decrease in the volume of the anterior cingulate cortex in OAs (Resnik, Pham, Kraut, Zonderman, & Davatzikos, 2003), as this brain area is associated with processing of sad faces (Blair, Morris, Frith, Perrett, & Dolan, 1999). Furthermore, the basal ganglia is believed to be spared from aging effects and is related to processing of happy faces (Phan, Wager, Taylor, & Liberzon, 2002) and disgust faces (Calder et al., 2001), hence the preserved neurological functioning may account for the maintenance with age of disgust and happy recognition from faces (Calder et al., 2003). However, a neurological explanation would also suggest that OAs maybe less able to recognise fear compared to YAs as there is evidence that activity in the amygdala declines with age and the

amygdala is an important processor of facial displays of fear (Gunning-Dixon et al., 2003; Phillips et al., 1998). However, the current findings suggest that age-related changes in amygdala functioning do not compromise the ability to recognise fear in older age. It is often difficult to relate behavioural outcomes, such as emotion

recognition ability, to specific by neurological activity (Hedden & Gabrieli, 2004) but further investigation using modern brain imaging techniques is warranted to increase our understanding regarding the effects of neurological changes on emotion recognition ability in OAs. This will enable research to move beyond correlational associations to establish causation of neurological changes and recognition ability for specific

emotions.

Given that OAs and YAs did not differ in levels of empathy, fluid intelligence, and extroversion it is unlikely that these skills and traits may account for the age-related differences in emotion recognition abilities reported here. Furthermore, OAs were not disadvantaged compared to YAs on many characteristics, such as positive and negative affect, anxiety, alexithymia, openness and conscientiousness, that may reduce emotion recognition ability (e.g., Cook, Brewer, Shah, & Bird, 2013; Schmid & Mast, 2010).

Thus, it is unlikely that difficulties for OAs to recognise anger compared to YAs are a function of these abilities. However, it could be argued that the characteristics of the YA participants in the current study for instance, lower positive affect, alongside higher negative affect, neuroticism, and alexithymia compared to OAs, may lower YAs’ ability to make accurate emotion recognition judgements. If this were the case then the current findings of largely preserved emotion recognition ability in OAs may reflect difficulties in emotion recognition ability in YAs rather than maintained ability of OAs. However, YAs’ ability to recognise happiness appears to be at ceiling suggesting that the YAs had good emotion recognition ability, at least for happiness.

The discussion will now turn to comparing accuracy on the emotion recognition and non-emotion tasks in YAs and OAs. The documented similarities between the emotion and non-emotion tasks allows for confident comparisons between the two. In the current study accuracy was lower on the emotion task than the non- emotion task and OAs and YAs did not differ in accuracy across the two tasks. The latter finding suggests that OAs were as able as YAs to meet the demands of the task. It is likely, therefore, that the age-related decline for anger recognition is not a result of OAs’ inability to meet the demands of the task. However, when comparing YAs, younger-older, and older-older adults’ accuracy across the emotion and non-emotion tasks, older-older adults were less accurate than both of the younger age groups. Furthermore, the age-related decline in accuracy on the emotion recognition and non-