A differential outcomes effect using biologically neutral outcomes in delayed matching-to-sample with pigeons

The differential outcomes effect (DOE) pertains to enhanced conditional discrimination performance if each correct stimulus-choice sequence is always followed by a different outcome (e.g., food vs. water) compared to when each correct sequence is followed equally often by either outcome. The present experiments sought evidence of a DOE in pigeons, using biologically neutral outcomes. Experiment 1 replicated findings with rats demonstrating that a DOE can occur when one outcome is a biologically neutral light and the other is the absence of that light. Experiment 2 extended these findings by demonstrating a DOE when two biologically neutral outcomes of similar sensory and associative properties were employed.     

Resolving the small-pockets problem helps clarify the role of education and political ideology in shaping vaccine scepticism

Understanding the factors associated with vaccine scepticism is challenging because of the ‘small-pockets’ problem: The number of highly vaccine-sceptical people is low, and small subsamples such as these can be missed using traditional regression approaches. To overcome this problem, the current study (N = 5,200) used latent profile analysis to uncover six profiles, including two micro-communities of vaccine-sceptical people who have the potential to jeopardize vaccine-led herd immunity. The most vaccine-sceptical group (1.14%) was highly educated and expressed strong liberal tendencies. This group was also the most sceptical about genetically modified crops and nuclear energy, and most likely to receive news about science from the Internet. The second-most vaccine-sceptical group (3.4%) was young, poorly educated, and politically extreme (both left and right). In resolving the small-pockets problem, the current analyses also help reconcile competing theoretical perspectives about the role of education and political ideology in shaping anti-vaccination views.     

Single band amplitude envelope cues as an aid to speechreading

Amplitude envelopes derived from speech have been shown to facilitate speech-reading to varying degrees, depending on how the envelope signals were extracted and presented and on the amount of training given to the subjects. In this study, three parameters related to envelope extraction and presentation were examined using both easy and difficult sentence materials: (1) the bandwidth and centre frequency of the filtered speech signal used to obtain the envelope; (2) the bandwidth of the envelope signal determined by the lowpass filter cutoff frequency used to “smooth” the envelope fluctuations; and (3) the carrier signal used to convey the envelope cues. Results for normal hearing subjects following a brief visual and auditory-visual familiarization/training period showed that (1) the envelope derived from wideband speech does not provide the greatest benefit to speechreading when compared to envelopes derived from selected octave bands of speech; (2) as the bandwidth centred around the carrier frequency increased from 12.5 to 1600 Hz, auditory-visual (AV) performance obtained with difficult sentence materials improved, especially for envelopes derived from high-frequency speech energy; (3) envelope bandwidths below 25 Hz resulted in AV scores that were sometimes equal to or worse than speechreading alone; (4) for each filtering condition tested, there was at least one bandwidth and carrier condition that produced AV scores that were significantly greater than speech-reading alone; (5) low-frequency carriers were better than high-frequency or wideband carriers for envelopes derived from an octave band of speech centred at 500 Hz; and (6) low-frequency carriers were worse than high-frequency or wideband carriers for envelopes derived from an octave band centred at 3150 Hz. These results suggest that amplitude envelope cues can provide a substantial benefit to speechreading for both easy and difficult sentence materials, but that frequency transposition of these signals to regions remote from their “natural” spectral locations may result in reduced performance.