Depressed mothers use less of the exaggerated prosody that is typical of infant-directed (ID) speech than do nondepressed mothers. We investigated the consequences of this reduced perceptual salience in ID speech for infant learning. Infants of nondepressed mothers readily learned that their mothers' speech signaled a face, whereas infants of depressed mothers failed to learn that their mothers' speech signaled the face. Infants of depressed mothers did, however, show strong learning in response to speech produced by an unfamiliar nondepressed mother. These outcomes indicate that the reduced perceptual salience of depressed mothers' ID speech could lead to deficient learning in otherwise competent learners.

The effectiveness of infant-and adult-directed (ID and AD) speech as signals for adult faces was studied. In the pairing phase of Experiment 1, 4-month-olds received 6 presentations of an ID or AD speech segment that either preceded (forward pairings) or followed (backward pairings) the presentation of a smiling face. In the summation test phase, infants received 4 novel checkerboard pattern presentations, 2 with and 2 without the speech segment. Only infants in the ID forward pairing condition exhibited significant positive summation. In Experiment 2, the differences between ID and AD forward pairing groups were replicated with different speech exemplars. In Experiment 3, an ID speech segment that was paired with a smiling or sad face elicited significant positive summation, while one paired with a fearful or angry face did not. These differences in visual responding were not accompanied by differences in infant facial affect. Ways in which ID speech may facilitate associative learning are discussed.The infant-directed (ID) speech of adults, which is characterized by higher overall frequency, greater frequency variability, and exaggerated prosody relative to adult-directed (AD) speech (Fernald & Simon, 1984;Fernald et al., 1989; Grieser & Kuhl, 1988), has been posited by Fernald (1984) and others (Papousek, Papousek, & Symmes, 1991;Stern, Spieker, & MacKain, 1982) to affect several aspects of infant responsiveness in the caregiver-infant dyad. These include engaging and maintaining attention, modulating arousal levels, communicating affect, and facilitating learning and information-processing. A growing number of studies have confirmed the predicted effects of ID speech on infant attention (

The role of the relative durations of conditioned stimulus-unconditioned stimulus (CS-US) gap and intertrial interval (ITI) were studied in two trace autoshaping experiments. In Experiment 1, CS-US gap duration was held constant at 12 s, and the duration of the ITI was systematically varied from IS s to 240 s across five groups of pigeons. Conditioned excitation (CS-approach) emerged at ITIs greater than 60 s, whereas conditioned inhibition (CS-withdrawal) emerged at ITIs less than 60 s. In Experiment 2, the time between successive USs averaged 87 s for all birds, and the duration of the CS-US gap was systematically varied from 6 s to 72 s across seven groups. Conditioned excitation was observed only in the 6-s gap condition, and conditioned inhibition developed in the 24-s through 72-s gap conditions. These findings indicate that the relative durations of CS-US gap and the ITI (or the interreinforcement interval [IRI]) are more important than is the absolute degree of CS-US contiguity in determining whether and what type of conditioning occurs on trace arrangements. Implications for theoretical treatments of contiguity in conditioning are discussed.Trace conditioning procedures, which in-conditioned responses (CRs) than are procevolve conditioned stimulus (CS) presentation dures in which (a) the CS remains on until or followed after an unfilled temporal gap by un-beyond the moment of US delivery, that is, conditioned stimulus (US) delivery, are less delay conditioning, or (b) some other discrete likely to lead to the acquisition of excitatory external stimulus intervenes id the gap between CS and US, that is, serial conditioning (Kamin,

Child-directed (CD) speech segments produced by 20 mothers who varied in self-reported symptoms of depression, recorded during a structured play interaction with their 2- to 6-month-old infants, were used as conditioned stimuli with face reinforcers in a conditioned attention paradigm. After pairings of speech segments and faces, speech segments were assessed for their ability to increase time spent looking at a novel checker-board pattern (summation test) using 225 4-month-old infants of nondepressed mothers. Significant positive summation, an index of associative learning, was obtained in groups of infants tested with speech produced by mothers with comparatively fewer self-reported symptoms of depression (Beck Depression Inventory or BDI < or = 15). However, significant positive summation was not achieved using speech samples produced by mothers with comparatively more symptoms of depression (BDI > 15). These results indicate that the CD speech produced by mothers with symptoms of depression does not promote associative learning in infants.

In four experiments pigeons were exposed to key-light illuminations separated from food delivery by 12-60 sec. Approach to the key light did not develop on conventional trace-conditioning arrangements but occurred consistently whenever some auditory or visual stimulus (a) filled the CS-US gap (serial conditioning) or (b) was always present except during the gap. Various comparison groups showed that this enhancement of conditioning cannot be mainly attributed to similarity between the CS and the added stimulus, or to spread of specific responses evoked by that stimulus, or to potentiation of CS's neural aftereffects by the extra stimulus. However, modifications of condition b in the final experiment revealed that CS approach was strong only when the stimulus present during the intertrial interval remained on until the termination of CS; if the stimulus ended at CS onset, conditioning did not occur. Although discriminability of CS-US gaps from intertrial periods seems necessary for conditioning to occur in the absence of close CS-US contiguity, the outcome of the final experiment indicates that such discriminability is not sufficient for conditioning. The results are primarily interpreted in terms of (a) possible second-order conditioning effects and (b) changes in the associative strength of the "local context" existing when CS appears, which may lead to superconditioning of CS.